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A T Dorsey

Publications and source records attributed to A T Dorsey.

At least 19 recordsLinked to original sources
PubMed2001

Observability of quantum phase fluctuations in cuprate superconductors.

We study the order parameter phase fluctuation effects in cuprate superconductors near T = 0, using a quasi-two-dimensional d-wave BCS model. An effective phason theory is obtained which is used to estimate the strength of the fluctuations, the fluctuation correction to the in-plane penetration depth, and the pair-field susceptibility. We find that, while the phase fluctuation effects are difficult to observe in the renormalization of the superfluid phase stiffness, they may be observed in a pair tunneling experiment which measures the pair-field susceptibility.

Journal Article↗
PubMed2001

Is brachytherapy comparable with radical prostatectomy and external-beam radiation for clinically localized prostate cancer?

PURPOSE: The aim of this study was to summarize the prostate brachytherapy literature and provide a comparative analysis of brachytherapy, radical prostatectomy, and external-beam radiation therapy outcomes for early-stage carcinoma of the prostate gland. MATERIALS AND METHODS: Published literature on brachytherapy, radical prostatectomy, and external-beam radiation therapy for clinically localized carcinoma ofthe prostate gland was reviewed. In addition, MEDLINE searches were performed to ensure completeness of the knowledge base. RESULTS: For patients with low-risk features, the biochemical results of prostate brachytherapy are as favorable as the most positive radical prostatectomy and external-beam radiation therapy series. In most studies, patients with intermediate- and high-risk disease have more durable biochemical outcomes when treated with brachytherapy (with or without external-beam radiation therapy). Long-term urinary morbidity is primarily restricted to patients with a history of transurethral resection. Significant bowel dysfunction is uncommon. Although erectile dysfunction occurs in approximately 50% of patients at 5 years, 80% respond favorably to sildenafil. Multiple postoperative dosimetric studies supported the ability of brachytherapists to adequately encompass the target volume. Compared with radical prostatectomy and external-beam radiation therapy, the total cost of prostate brachytherapy is 20% less. CONCLUSIONS: With prostate-specific antigen-based follow-up as long as 10 years, the results of prostate brachytherapy for low-risk patients are as favorable as the most positive radical prostatectomy and external-beam radiation therapy series. In most reports, intermediate- and high-risk patients have more durable biochemical outcomes when managed by brachytherapy approach (with or without external-beam radiation therapy). Serious complications following brachytherapy are relatively rare.

Brachytherapy↗
PubMed2001

Effect of prostate size and isotope selection on dosimetric quality following permanent seed implantation.

PURPOSE: The aim of this study was to assess retrospectively the influence of prostate size and the effect of isotope selection on implant quality in patients undergoing transperineal ultrasound-guided permanent prostate brachytherapy. PATIENTS AND METHODS: Two hundred forty-eight consecutive patients without prior transurethral resection of the prostate gland underwent permanent seed implantation using either iodine 125 or palladium 103 as monotherapy or a boost following moderate doses of external-beam radiation therapy from January 1998 through November 1999. Postimplant dosimetry was obtained on day 0 using thin slice computed tomography (CT) scans. Dosimetric quality was reported in terms of the following parameters: D90, V100, V150, and V200, where D90 is defined as the minimum dose covering 90% of the prostate volume, and V100, V150, and V200 are defined as the percentage volume of the prostate receiving at least 100%, 150%, and 200% of the prescribed minimal peripheral dose (mPD), respectively. In addition, the urethral dose was evaluated. Preimplant prostate size was divided into the following categories: <20, 20-30, 30-40, 40-50, and >50 cm3. Prostate volume was determined via transrectal ultrasound volumetric study. In addition, within each of the five size categories, the effect of isotope on implant quality was evaluated. RESULTS: No statistically significant volume dependence in D90, V100, or urethral doses was discerned, whereas V150 and V200 were volume dependent. Between isotopes, the following differences in dosimetric quality were statistically significant: V100, V150, V200, and mean and medial urethral dose. 125I implants had higher values of V100 (95% vs. 94%, p = .004) and urethral dose (118% vs. 110% of mPD, p < .001), and 103Pd implants had higher V150 and V200 (57% vs. 51% and 31% vs. 22%, respectively). Only the isotopic differences in V200 persisted for all the volumetric subgroups. There was no significant overall volume dependence based on neoadjuvant hormone use or nonuse for any of the quality parameters analyzed. CONCLUSIONS: The most important indicators of the quality of dosimetric coverage, V100 and D90, were not dependent on preimplant prostate volume or use of neoadjuvant hormones. The mean, median, and maximum urethral doses also showed no dependence on prostate size. Although there were isotopic differences in day 0 dosimetric parameters following permanent prostate brachytherapy, we do not consider the magnitude of any of these differences to be clinically significant.

Aged↗
PubMed2000

Comparison of dose length, area, and volume histograms as quantifiers of urethral dose in prostate brachytherapy.

PURPOSE: To determine the magnitude of the differences between urethral dose-volume, dose-area, and dose-length histograms (DVH, DAH, and DLH, respectively, or DgH generically). METHODS AND MATERIALS: Six consecutive iodine-125 ((125)I) patients and 6 consecutive palladium-103 ((103)Pd) patients implanted via a modified uniform planning approach were evaluated with day 0 computed tomography (CT)-based dosimetry. The urethra was identified by the presence of a urinary catheter and was hand drawn on the CT images with a mean radius of 3.3 +/- 0.7 mm. A 0.1-mm calculation matrix was employed for the urethral volume and surface analysis, and urethral dose points were placed at the centroid of the urethra on each 5-mm CT slice. RESULTS: Although individual patient DLHs were step-like, due to the sparseness of the data points, the composite urethral DLH, DAH, and DVHs were qualitatively similar. The DAH curve delivered more radiation than the other two curves at all doses greater than 90% of the prescribed minimum peripheral dose (mPD) to the prostate. In addition, the DVH curve was consistently higher than the DLH curve at most points throughout that range. Differences between the DgH curves were analyzed by integrating the difference curves between 0 and 200% of the mPD. The area-length, area-volume, and volume-length difference curves integrated in the ratio of 3:2:1. The differences were most pronounced near the inflection point of the DgH curves with mean A(125), V(125), and L(125) values of 36.6%, 31.4%, and 23.0%, respectively, of the urethra. Quantifiers of urethral hot spots such as D(10), defined as the minimal dose delivered to the hottest 10% of the urethra, followed the same ranking: area analysis indicated the highest dose and length analysis, the lowest dose. D(10) was 148% and 136% of mPD for area and length evaluations, respectively. Comparing the two isotopes in terms of the amount of urethra receiving a given dose, (103)Pd implants were significantly cooler than (125)I implants over most of the range of clinical interest, from 100% to 150% of mPD. CONCLUSION: Dose gradients in prostate implants result in the observed ordering of DAH, DVH, and DLH from higher to lower doses. The three histogram approaches remain in close agreement up to 100% of the mPD but diverge at higher doses. Although urethral point doses are the most easily determined, they underestimate the amount of urethra at risk at higher doses compared to dose area analysis. Because dosimetric parameters detailing high-dose regions such as D(10) show only slight differences between calculation methods, they are recommended over the corresponding geometric entities G(150) or G(175). The differences between the D(gg) entities are sufficiently small that they are unlikely to be of clinical significance or to confound analyses attempting to correlate urinary morbidity with urethral dosimetry.

Brachytherapy↗
PubMed2000

A comparison of radiation dose to the neurovascular bundles in men with and without prostate brachytherapy-induced erectile dysfunction.

PURPOSE: The etiology of erectile dysfunction after definitive local therapy for carcinoma of the prostate gland represents a multifactorial phenomenon including neurogenic compromise, venous insufficiency, local trauma, and psychogenic causes. It has been suggested that impotence after prostate brachytherapy is a consequence of excessive radiation dose to the neurovascular bundles (NVB). Herein we evaluate the potential relationship between radiation dose to the NVB and the development of erectile dysfunction following prostate brachytherapy. METHODS AND MATERIALS: The radiation dose to the NVB was evaluated for 33 patients who developed erectile dysfunction (ED) following brachytherapy plus 21 additional patients who were potent before and subsequent to brachytherapy. Of the 54 patient study group, the median follow up was 37 months, and 25 patients were managed with (125)I as a monotherapeutic approach and 29 received (103)Pd as a boost following 45 Gy of external beam radiation therapy. Radiographic localization of the NVB was performed via a two-dimensional geometric model that placed 3-NVB calculation points on the left and right posterolateral side of each 5-mm CT slice. Parameters evaluated included dose-surface histograms, dose parameters via point doses on each slice, the magnitude of the dose in relationship to the distance from the base, and the relationship between NVB radiation dose in patients with and without ED, patient response to sildenafil and case sequence number. RESULTS: In terms of percent prescribed minimum peripheral dose (% mPD), there was no significant difference in mean neurovascular bundle dose between potent and impotent patients, between the isotopes ((125)I or (103)Pd), mono- or boost therapy, or side of the prostate for which the overall average was 217% +/- 55% of mPD. There was also no significant dosimetric difference in terms of response to sildenafil based on a multivariate analysis which included % mPD and various dose thresholds and side of the gland. The dose distribution over the length of the prostate rose smoothly from the base and apex to peak at midgland in (125)I implants while (103)Pd implants had a relatively constant dose over the length of the prostate. Considering the calculation grid as forming a 6-mm wide ribbon along each side of the prostate, the average patient had 70 mm(2) area receiving at least 300% of mPD. CONCLUSION: In this study, no relationship between radiation dose to the NVB and the development of post brachytherapy erectile dysfunction was discernible. Such a difference may become evident with additional follow-up. If long-term brachytherapy-induced erectile dysfunction is related to the radiation dose to the NVB, the ultimate preservation of potency following prostate brachytherapy may be markedly inferior to what has been reported. Nevertheless, the majority of this patient population responded favorably to sildenafil.

Age Factors↗
PubMed2000

Rectal function following prostate brachytherapy.

PURPOSE: Quality of life following therapeutic intervention for carcinoma of the prostate gland has not been well documented. In particular, a paucity of data has been published regarding bowel function following prostate brachytherapy. This study evaluated late bowel function in 209 consecutive prostate brachytherapy patients via a one-time questionnaire administered 16-55 months postimplant. MATERIALS AND METHODS: Two hundred nineteen consecutive patients underwent permanent prostate brachytherapy from April 1995 through February 1998 using either (125)I or (103)Pd for clinical T1c-T3a carcinoma of the prostate gland. Of the 219 patients, 7 had expired. Of the remaining 212 patients (median follow-up, 28 months), each patient was mailed a self-administered questionnaire (10 questions) with a prestamped return envelope; 209 (98.6%) surveys were returned. Clinical parameters evaluated for bowel dysfunction included patient age, diabetes, hypertension, history of tobacco consumption, clinical T-stage, elapsed time since implant, and prostate ultrasound volume. Treatment parameters included utilization of neoadjuvant hormonal manipulation, utilization of moderate dose external beam radiation therapy prior to implantation, choice of isotope ((125)I vs. (103)Pd), rectal dose (average, median and maximum doses), total implanted seed strength, values of the minimum dose received by 90% of the prostate gland (D(90)), and the percent prostate volume receiving 100%, 150%, and 200% of the prescribed minimum peripheral dose (V(100), V(150) and V(200), respectively). Because detailed baseline bowel function was not available for these patients, a cross-sectional survey was performed in which 30 newly diagnosed prostate cancer patients of comparable demographics served as controls. RESULTS: The total rectal function scores for the brachytherapy and control patients were 4.3 and 1.6, respectively, out of a total 27 points (p < 0.001). Of the evaluated clinical parameters, only the preimplant number of bowel movements per day were correlated with the total survey score (p < 0.01). None of the treatment parameters were significantly correlated with the total survey score. Despite the fact that implantation with (103)Pd resulted in lower radiation doses to the rectum, the choice of isotope was not predictive of bowel function scores. A trend toward increased rectal scores was noted for older patients, and a nonsignificant improvement in rectal survey scores was noted with elapsed time from implantation. Only 19.2% (40/208) of the treatment group reported a worsening of bowel function following implantation. Patient perception of overall rectal quality of life, however, was inversely related to the utilization of external beam radiation therapy (p = 0.034). CONCLUSION: To date, no severe changes in late bowel function have been noted following prostate brachytherapy. Although the survey scores indicate bowel function is worse after an implant, the minor changes are not significant enough to bother most individuals. Less than 20% of patients reported that their bowel function was worse following prostate brachytherapy.

Aged↗
PubMed2000

Temporal resolution of urinary morbidity following prostate brachytherapy.

PURPOSE: To report the short-term urinary morbidity for prostate brachytherapy patients without a preimplant history of a transurethral resection of the prostate gland and who received prophylactic and prolonged alpha-blockers. alpha-blockers may decrease radiation-induced urethritis and increase urinary flow. Multiple clinical and treatment parameters were evaluated to identify factors associated with increased acute urinary morbidity. MATERIALS AND METHODS: One hundred seventy consecutive patients without a prior history of a transurethral resection of the prostate gland underwent transperineal ultrasound guided prostate brachytherapy for clinical T1c-T3a carcinoma of the prostate gland. For all patients, an alpha-blocker was initiated prior to implantation and continued at least until the international prostate symptom score (IPSS) returned to baseline levels. Clinical parameters evaluated for short-term urinary morbidity included patient age, clinical T stage, preimplant IPSS (obtained within 3 weeks of implantation), and prostate ultrasound volume. Treatment parameters included the utilization of neoadjuvant hormonal manipulation, the utilization of moderate dose external beam radiation therapy before implantation, the choice of isotope, the urethral dose, the total implant activity in millicuries, and a variety of dosimetric quality indicators (D(90) and V(100)/V(150)/V(200)). Catheter dependency and the duration of alpha-blocker dependency was also evaluated. On average, 11.2 IPSS surveys were obtained for each patient. RESULTS: One hundred fifty of the 170 patients (88.2%) had the urinary catheter permanently removed on day 0. Only one patient required an urinary catheter for > 5 days. Two patients (1.2%) required a subsequent transurethral resection of the prostate gland because of prolonged obstructive/irritative symptoms. To date, no patient has developed an urinary stricture or urinary incontinence. The IPS score on average peaked at 2 weeks following implantation. This score returned to within 1 point of the antecedent value at a median of 6 weeks and a mean of 13.3 weeks. At 26 and 50 weeks, 85% and 56% of the patients, respectively, continued with alpha-blockers. Of the clinical and treatment parameters evaluated for short-term urinary morbidity, only variants of the IPSS such as the maximum, maximum increase, and preimplant IPSS values correlated with time to return to the referent zone with p < 0.05. CONCLUSION: The return of the IPS score to baseline occurred more rapidly in our series than what has previously been reported. The 1.2% incidence of transurethral resections also compares favorably with the published literature. We believe these results may be due to maintaining the average urethral dose to approximately 115% of the prescribed dose and the prophylactic and long-term use of alpha-blockers.

Adrenergic alpha-Antagonists↗
PubMed2000

Seed fixity in the prostate/periprostatic region following brachytherapy.

PURPOSE: Although postoperative dosimetric analyses of prostate brachytherapy are commonly reported, the long-term persistence, or fixity, of seeds implanted in the prostate gland and periprostatic region remains unclear, with only a few reports regarding the loss or migration of the seeds in the implanted region and none which correlate lung embolization to pelvic seed loss. METHODS AND MATERIALS: The study population consisted of 175 consecutive patients implanted with either 125I (95 patients) or 103Pd (80 patients) using a mean of 136 seeds in a modified uniform loading approach to cover a planning volume that was 1.64 times the ultrasound prostate volume. An average of 64% of 125I seeds were embedded in braided vicryl suture, and these seeds were used on the periphery and extra prostatic regions. Following CT-based dosimetric analysis on day 0, all patients had orthogonal plain films of the pelvis obtained from day 0 to day 502, with an average of 2.3 film pairs per patient. Routine diagnostic PA and lateral chest X rays were obtained for 156 patients over the same time period. RESULTS: The mean pelvic seed fixity was greater than 98% throughout the time covered by this study. The seed fixity rates for 125I and 103Pd, although nearly equal, were significantly different up to 60 days post implant. The median 125I seed loss per patient was only 1 seed through 180 days while for 103Pd, the median seed loss was 2 seeds at 28 and 60 days and 3 seeds at 180 days. The fraction of patients experiencing no seed loss decreased from 40% at 28 days to 20% at 180 days for 125I and from 24% to 7% for 103Pd over the same time interval. Patient and treatment parameters closely correlated to local seed loss include the number of seeds implanted, the planning volume, and the number of loose seeds, and for 125I, the fraction of seeds in suture. The fraction of seeds placed outside the gland was not correlated with seed loss. Of the seeds lost from the pelvis, about 10% were found to embolize to the lungs. Among the 156 patients with post-implant chest X rays, the fraction of patients with pulmonary seed embolization was 34/156 (21.8%). Of the 20 patients who had post-implant chest X rays obtained within 14 days of brachytherapy, none had seeds detected in the lungs, while of the 136 patients who had chest X rays obtained greater than 30 days following implantation, 25.0% (34 patients) were noted to have seeds visualized in the lungs. CONCLUSIONS: With a median follow-up of 9 months, 125I seeds embedded in a vicryl suture or 103Pd seeds can be safely implanted in the prostate and periprostatic tissue with a high probability of prostate bed seed fixity and a low incidence of radioactive seed embolization to the lungs.

Aged↗
PubMed2000

Modern prostate brachytherapy.

As computer-aided margin tools become more sophisticated, physicists will be increasingly called upon to convert ultrasound prostate volumes to expanded planning target volumes (PTVs) to treat adequately extracapsular disease. The American Association of Physicists in Medicine Task Group 43 formalism and the new National Institute of Standards and Technology calibration system suitable for single low-energy seeds have been crucial in smoothly implementing changes in established seeds and in incorporating data from new manufacturers. However, the lack of consensus on treatment design and evaluation has led to an uncomfortably wide spectrum of clinical practice, only part of which can be attributed to variations inherent to any surgical procedure due to the practitioner's skill. The relative merits of implanting the prostate and margin with a modified uniform seed-loading approach to create plans with a relatively homogeneous dose distribution and a corresponding low risk of overdosing critical structures are addressed. Likewise, the advantages of performing postoperative dosimetry at the physically optimum time of greater than 2 weeks post implant are contrasted with the clinical advantages of obtaining the dosimetry as soon as possible. Proposed lower limits for quality parameters such D90 and V100 are reviewed. Measures of doses to the urethra, rectum, and neurovascular bundles are presented, along with correlations between various dosimetric parameters and other patient specific data with quality of life metrics involving urinary incontinence, rectal damage, and sexual dysfunction.

Brachytherapy↗
PubMed2000

The effect of constipation on rectal dosimetry following prostate brachytherapy.

The purpose of this study is to report the effect of dilatation of the anorectum on rectal dosimetry following an 125I prostate implant. Three months following prostate brachytherapy, 2 computed tomography (CT) scans of the prostate gland were obtained within 90 minutes of each other. The first CT scan revealed a dilated anorectum secondary to constipation. The second CT was obtained following the administration of an enema with a successfully evacuated rectum. Differences in radiation doses to the distended and empty rectum were computed via the mean dose, the maximum dose per slice, the distance from the base, and in terms of the surface of the anterior quadrant of the rectum receiving 100%, 125%, 150%, 175%, 200%, and 250% of the prescribed dose. The dose to the rectal wall was substantially increased in the distended state for all evaluated parameters. In general, the mean dose to the rectal wall was increased by a factor of 1.5 in the distended state. In both scenarios, the dose to the rectal wall peaked near midgland. In terms of 10 degrees rectal wall sectors receiving a given percentage of the prescribed minimal peripheral dose, S%mPD, the S100, S125, S150, S175, S200, and S250 were substantially greater for the distended versus the empty rectum. The magnitude of the percentage difference in dose between the distended and evacuated rectum increased with dose level while the difference in the number of sectors receiving a given dose level was greatest at 125% and 150% of the prescribed dose. We recommend detailed postimplant attention to bowel habits for at least 2 half-lives of the implanted isotope to minimize rectal distention, decrease radiation dose to the anterior rectal wall, and subsequently minimize potential constipation related rectal toxicity.

Adenocarcinoma↗
PubMed2000

Comparison of seed loading approaches in prostate brachytherapy.

Since uniform seed loading in prostate brachytherapy can produce an intolerably high dose along the urethra, some form of peripheral loading is commonly employed. We define three variants of peripheral loading and compare them in a small, medium, and large prostate in terms of coverage of the planning target volume (PTV), homogeneity, and ability to spare critical structures of excessive dose. Modified uniform loading has at least 2/3 of the seeds occupying sites on a 1 cm cubic grid keyed to the prostate base and the posterior border of the prostate. Nonuniform loading explicitly spares the urethra by using only basal and apical seeds in at least two centrally located needles. Peripheral loading uses higher activity seeds with the posterior implant plane 5 mm anterior to the posterior border of the prostate. The three prostate volumes (18.7, 40.7, and 60.2 cm3 by ultrasound) were expanded to planning volumes (32.9, 60.0, and 87.8 cm3, respectively). The planning volumes (PTVs) were loaded with a 125I seed distribution and activity sufficient to cover 99.7+/-0.3% of the PTV with the prescribed minimal peripheral dose (mPD) of 145 Gy. Activities used ranged from 0.32 to 0.37 mCi/seed (0.41-0.47 U/seed) for the first two approaches and from 0.57 to 0.66 mCi (0.72-0.84 U) for peripheral loading. Modified uniform loading produced the most uniform distribution based on dose-volume histograms and the volume receiving >150% of prescribed dose. All the approaches are capable of constraining the superior-inferior dose profile (the urethral path) to less than 150% of the mPD, but the nonuniform approach with explicit urethral sparing kept the urethral dose below 120% of the mPD. Dose profiles for the three approaches along the posterior-anterior midline axis are comparable near the urethra, but peripheral and nonuniform approaches have extended regions where the dose is >150% of mPD. These regions approach within 10 mm of the rectum or urethra, so these two approaches require greater accuracy in intraoperative execution of the plan. Although each of the three planning approaches can achieve the treatment goals of adequate coverage and critical structure sparing, modified uniform loading has a more homogeneous dose distribution. This approach may be more forgiving of systematic errors in seed placement.

Algorithms↗
PubMed2000

Isotope choice and the effect of edema on prostate brachytherapy dosimetry.

In prostate brachytherapy, post implant dosimetry quality parameters may be strongly affected by edema brought on by the trauma of the implant procedure since the amount of edema and the time course of its resolution are highly variable from patient to patient. Edema was simulated from preplans on three prostates which had ultrasound prostate volumes of 18.7, 40.7 and 60.2 cm3 expanded to planning volumes of 32.9, 60.0 and 87.8 cm3, respectively. The preplans were designed so that identical seed distributions for a given prostate gave virtually identical target dose coverage of 99.7+/-0.3% of the planning volume when using either 125I or 103Pd. Simulated CT edema volume expansions of 0%, 10%, 20% and 30% were imposed anisotropically in accordance with clinical observations so that the expansion in the superior-inferior direction was twice that of the transverse dimensions. Dose-volume histograms (DVHs) were analyzed for each prostate as a function of isotope and degree of edema. The 103Pd implants were more greatly affected by fixed amounts of edema than 125I implants, and the slopes of the DVH curves indicate less homogeneity from 103Pd implants. The DVHs were then weighted according to the portion of the isotope decay curve occupied by each edema step for half-lives of edema resolution of 5, 10 and 20 days which are within the range of clinically observed resolution times. The weighted DVHs were summed to give a net DVH corresponding to the overall dynamic effect of edema. A greater fraction of the defined prostate volume received doses in the range of likely therapeutic significance, from 75% to 125% of the prescribed minimal peripheral dose (mPD), from 125I implants than from 103Pd implants. These differences in dosimetric quality arise from two differences in the physical properties of the isotopes: more rapid attenuation of 103Pd photons with distance creates cool spots in an edematous prostate, and the shorter half-life of 103Pd causes a greater fraction of the isotope decay to consist of the prostate in an edematous state. An increase in 103Pd seed strength by about 10% beyond that required to achieve equal coverage with an identical seed distribution using 125I should minimize the differences brought on by edema.

Biophysical Phenomena↗
PubMed2000

Influence of prophylactic dexamethasone on edema following prostate brachytherapy.

PURPOSE: This work evaluates the prophylactic administration of dexamethasone as an adjunct to prostate brachytherapy to determine the effect of dexamethasone on postimplant edema, dosimetric quality, catheter dependency, and clinical outcome as assessed by serial American Urological Association (AUA) symptom score determinations. MATERIALS AND METHODS: In a controlled study, 22 unselected patients were placed alternately into either a dexamethasone or control arm. RESULTS: There was no statistically significant difference in volume between the experimental and control groups on either day 0 or day 28. Accordingly, the day 0 dosimetric parameters, short-term catheter dependency, and serial AUA symptom score determinations were equivalent in both patient groups. However, the patients receiving dexamethasone had a markedly smaller volume on day 3, but 9 of 11 experienced rebound edema with a volume on day 14 significantly greater than day 3. CONCLUSIONS: Because of the small number of patients evaluated, additional studies are essential to confirm these findings. At the present time, we do not recommend this dexamethasone schedule as a routine component of prostate brachytherapy.

Brachytherapy↗
PubMed1999

The dependence of prostate postimplant dosimetric quality on CT volume determination.

PURPOSE: The postoperative evaluation of permanent prostate brachytherapy requires a subjective determination of the implant volume. This work investigates the magnitude of the effect that various methods of treatment volume delineation have on dosimetric quality parameters for a treatment planning philosophy that defines a target volume as the prostate with a periprostatic margin. METHODS AND MATERIALS: Eight consecutive prostate brachytherapy patients with a prescribed dose of 145 Gy from 125I as monotherapy comprised the study population. The prostate ultrasound volume was enlarged to a planning volume by an average factor of 1.8 to encompass probable extracapsular extension in the periprostatic region. For this cohort, the mean pretreatment parameters were 30.3 cm3 ultrasound volume, 51.8 cm3 planning volume, 131 seeds per patient, and 42.9 mCi total activity. On CT study sets obtained less than 2 hours postoperatively, target volumes were drawn using three methods: prostate plus a periprostatic margin, prostate only which excluded the puborectalis muscles, the periprostatic fat and the periprostatic venous plexus, and the preplanning ultrasound magnified to conform to the magnification factor of the postimplant CT scan. Three sets of 5 dosimetric quality parameters corresponding to the different volumetric approaches were calculated: V100, V150, and V200 which are the fractions of the target volume covered by 100, 150, and 200% of the prescribed dose, and D90 and D100, which are the minimal doses covering 90 and 100% of the target volume. RESULTS: The postoperative CT volume utilizing the prostate plus margin technique was comparable to the initial planning volume (mean 55.5 cm3 vs. 51.8 cm3, respectively) whereas those determined via superimposing the preplan ultrasound resulted in volumes nearly identical to the initial ultrasound evaluation (mean 32.4 cm3 vs. 30.3 cm3). The prostate only approach resulted in volumes approximately 25% larger than the ultrasound volume approach. Despite the volume determinations being markedly different, no significant differences between the approaches were appreciated for V100, V150, V200, and D90. Large variations seen in D100 were uncorrelated to any of the other parameters and make D100 unsuitable as a quality indicator. CONCLUSIONS: In terms of a logarithmic measure, the variation between volumetric approach for V100, V150, V200, and D90 was less than one-fifth the variation of the CT volumes. These results which indicate relative independence of postimplant CT volume determination and dosimetric quality are only valid for a planning philosophy that includes the prostate with a periprostatic margin as the target volume.

Brachytherapy↗
PubMed1999

Potential role of various dosimetric quality indicators in prostate brachytherapy.

PURPOSE: Postoperative CT-based dosimetric analysis provides detailed information regarding the coverage and uniformity of an implant, but the assessment of implant quality remains an unanswered and controversial issue. There is no disagreement that a good implant should cover the target volume with an adequate dose, but there is no consensus as to what represents an adequate dose. MATERIALS AND METHODS: The American Brachytherapy Society has recently proposed that prostate brachytherapy quality be measured in terms of the following parameters: D90, V100, and V150 where D90 is defined as the minimal dose covering 90% of the prostate volume and V100 and V150 are defined as the percent volume of the prostate receiving at least 100% or 150% of the prescribed minimal peripheral dose (mPD), respectively. We report detailed day 0 dosimetric evaluation for 60 consecutive prostate brachytherapy patients implanted via a standard transperineal ultrasound guided approach in terms of D90, D100, V90, V100, and V150 and also the maximal and average rectal and urethral dose. RESULTS: Dosimetric evaluation resulted in a V100 greater than 80% of the prostate volume and a D90 greater than 90% of the mPD in the entire patient population. There was a statistically significant difference between the quality scores of 125I implants and 103Pd implants with the 125I mean V100 and D90 at 95.3% volume and 109.9% mPD, respectively, vs. 103Pd at 91.8% volume and 103.7% mPD. Likewise, the rectal and urethral doses as a fraction of mPD were significantly lower in 103Pd than in 125I implants. This occurred despite the fact that palladium implants were typically preplanned with significantly better coverage and hotter V150 than iodine implants. We consider V150 to be an important parameter for determining dose homogeneity although the clinical utility of dose homogeneity remains unknown. The mean V150 was 45.6 +/- 9.6% volume. There was no additional dosimetric utility from a determination of V90 while D100 was found to be overly sensitive to steep dose gradients at the periphery of the prostate. CONCLUSIONS: This report represents the first detailed postimplant day 0 dosimetric evaluation comparing ABS recommended quality parameters used to evaluate prostate brachytherapy. At the present time, no long-term clinical outcomes are available because of short follow-up. As PSA based follow-up data becomes available, however, this report may help define what represents an adequate implant.

Brachytherapy↗
PubMed1999

Rectal dosimetric analysis following prostate brachytherapy.

PURPOSE: To retrospectively assess the rectal tolerance dose in transperineal ultrasound-guided prostate brachytherapy using easily measured point doses. METHODS AND MATERIALS: Forty-five consecutive patients who underwent prostate seed implantation from January 1996 to October 1996, using either 125I or 103Pd as monotherapy or as a boost following 45 Gy of external beam radiotherapy (XRT), were evaluated. For monotherapy using 125I, the minimal peripheral dose (mPD) was 160 Gy, utilizing dosimetry parameters which are equivalent to 144 Gy under the American Association of Physicists in Medicine Task Group 43 (AAPM TG43) recommendations. Computed tomography (CT)-based dosimetry was performed within 9 days of the implant, with a urinary catheter in place for identification of the urethra, and a rectal obturator positioned prior to the CT scan for identification of the anterior rectal mucosa. Dosimetric parameters relevant to this study were the average, maximal and minimal anterior rectal mucosal dose, and the surface area and length of the anterior rectal mucosa irradiated to 50%, 75%, 90%, 100%, and 120% of the prescribed dose. Rectal complications were determined by patient reporting during office visits and telephone follow-up. Follow-up ranged from 19 to 28 months (median 23). RESULTS: Among the four cohorts, the average anterior rectal mucosal dose as a percent of the prescribed mPD was 82.5% +/- 14.1% (standard deviation, SD), and the average maximum was 120% +/- 35%. The length of the rectum receiving a given dose was found to be correlated with the rectal surface area receiving that dose (r2 = 0.82 - 0.93 over the dose range 0.5-1.2 mPD). Rectal complications occurred in only four patients, and consisted of mild, self-limited proctitis. Three of the four were in the top quartile of average and maximal rectal dose and length of rectum receiving > or = 100% of mPD, while the fourth was in the bottom quartile of these parameters. In terms of surface area, all four patients were in the upper half of the study group, with > or = 90 mm2 at dose levels > or = 100% of mPD. CONCLUSION: Our results indicate that in an implant program which maintains the anterior rectal mucosa point dose averages to about 85% of the prescribed dose (regardless of the choice of isotope or the treatment approach), the average maximum to 120% of mPD, and the length of the anterior rectal mucosa receiving 100% and 120% of the prescribed dose at approximately 10 mm and 5 mm, respectively, the incidence of mild self-limited proctitis will be in the range of approximately 9%, without incidence of rectal ulceration and/or fistula formation.

Brachytherapy↗
PubMed1999

Efficacy of sildenafil citrate in prostate brachytherapy patients with erectile dysfunction.

OBJECTIVES: To ascertain the efficacy of sildenafil citrate (Viagra) in patients with erectile dysfunction (ED) either before or after prostate brachytherapy by an open-label, nonrandomized study. METHODS: Sixty-two patients who underwent prostate brachytherapy between March 1995 and July 1998, had ED either before or after brachytherapy, and were interested in treatment with sildenafil comprised the patient population. Clinical and treatment parameters evaluated for medication efficacy included patient age at brachytherapy and at medication administration, hypertension, diabetes, smoking history, onset of ED, potency status before implant, frequency of intercourse before brachytherapy (if potent), use of neoadjuvant hormonal manipulation, use of moderate dose external beam radiation therapy before implantation, choice of isotope, V100 (the percentage of the prostate volume receiving at least 100% of the prescribed minimal peripheral dose), and sildenafil dose. RESULTS: Fifty (80.6%) of 62 patients responded favorably to sildenafil. None of the treatment parameters predicted medication failure, and among the clinical parameters, only diabetes predicted failure (3 of 5) and only with borderline statistical validity (P = 0.046). CONCLUSIONS: Our results suggest brachytherapy-induced impotence is as amenable to sildenafil treatment as ED from other causes. In addition, our 80.6% success rate is comparable to reported results for patients who underwent bilateral nerve-sparing radical prostatectomy and significantly better than patients who underwent unilateral nerve-sparing or non-nerve-sparing approaches.

Adenocarcinoma↗