Search PubMed⌕ Search

Biomedical subjects

Deborah A Kuban

Publications and source records attributed to Deborah A Kuban.

At least 19 recordsLinked to original sources
PubMed2006

The predictive value of 2-year posttreatment biopsy after prostate cancer radiotherapy for eventual biochemical outcome.

PURPOSE: To determine the value of a 2-year post-radiotherapy (RT) prostate biopsy for predicting eventual biochemical failure in patients who were treated for localized prostate cancer. METHODS AND MATERIALS: This study comprised 164 patients who underwent a planned 2-year post-RT prostate biopsy. The independent prognostic value of the biopsy results for forecasting eventual biochemical outcome and overall survival was tested with other factors (the Gleason score, 1992 American Joint Committee on Cancer tumor stage, pretreatment prostate-specific antigen level, risk group, and RT dose) in a multivariate analysis. The current nadir + 2 (CN + 2) definition of biochemical failure was used. Patients with rising prostate-specific antigen (PSA) or suspicious digital rectal examination before the biopsy were excluded. RESULTS: The biopsy results were normal in 78 patients, scant atypical and malignant cells in 30, carcinoma with treatment effect in 43, and carcinoma without treatment effect in 13. Using the CN + 2 definition, we found a significant association between biopsy results and eventual biochemical failure. We also found that the biopsy status provides predictive information independent of the PSA status at the time of biopsy. CONCLUSION: A 2-year post-RT prostate biopsy may be useful for forecasting CN + 2 biochemical failure. Posttreatment prostate biopsy may be useful for identifying patients for aggressive salvage therapy.

Aged↗
PubMed2006

Nadir prostate-specific antigen within 12 months after radiotherapy predicts biochemical and distant failure.

OBJECTIVES: To determine whether nadir prostate-specific antigen (PSA) levels within 12 months (nadir PSA12) after completion of radiotherapy (RT) can be used as an early marker of recurrence risk. METHODS: A total of 4839 patients were treated with RT and without hormonal therapy from 1986 to 1995 for Stage T1-T2 prostate cancer at nine institutions. Of these 4839 patients, 4833, with a median follow-up of 6.3 years, met the criteria for analysis. The study endpoints included freedom from PSA failure, initiation of androgen deprivation, or documented local or distant failure (PSA-DFS); freedom from clinically apparent distant metastasis (DMFS); and overall survival (OS). RESULTS: Patients with a nadir PSA12 of 2.0 ng/mL or less had an 8-year PSA-DFS, DMFS, and OS rate of 55%, 95%, and 73%, respectively, compared with 40%, 88%, and 69%, respectively, for patients with a nadir PSA12 of more than 2.0 ng/mL. Multivariate analysis confirmed that a nadir PSA12 of greater than 2 ng/mL was an independent predictor of PSA-DFS, DMFS, and OS. Classification and regression tree analysis identified the nadir PSA12 levels after RT associated with PSA-DFS, DMFS, and OS. Nadir PSA12, combined with the pretreatment PSA level, identified patients at particularly high risk of distant metastasis. CONCLUSIONS: The results of this large, multi-institutional study have demonstrated that nadir PSA12 is predictive of clinical outcomes for patients with localized prostate cancer after RT. A high pretreatment PSA level and high nadir PSA12 will identify patients at particularly high risk who might benefit from early adjuvant therapy.

Adenocarcinoma↗
PubMed2006

Multi-institutional analysis of long-term outcome for stages T1-T2 prostate cancer treated with permanent seed implantation.

PURPOSE: To assess long-term prostate-specific antigen (PSA) outcome after permanent prostate brachytherapy (BT) and identify predictors of improved disease-free survival. METHODS AND MATERIALS: Eleven institutions combined data on 2,693 patients treated with permanent interstitial BT monotherapy for T1-T2 prostate cancer. Of these patients, 1,831 (68%) were treated with I-125 (median dose, 144 Gy) and 862 (32%) were treated with Pd-103 (median dose, 130 Gy). Criteria for inclusion were: available pre-BT PSA, BT > or =5 years before data submission, BT between 1988-1998, and no androgen deprivation before failure. The median follow-up was 63 months. RESULTS: Among patients where the I-125 dose to 90% of the prostate (D90) was > or =130 Gy, the 8-year PSA relapse-free survival (PRFS) was 93% compared with 76% for those with lower D90 dose levels (p < 0.001). A multivariable analysis identified tumor stage (p = 0.002), Gleason score (p < 0.001), pretreatment PSA level (p < 0.001), treatment year (p = 0.001), and the isotope used (p = 0.004) as pretreatment and treatment variables associated with PRFS. When restricted to patients with available postimplantation dosimetric information, D90 emerged as a significant predictor of biochemical outcome (p = 0.01), and isotope was not significant. The 8-year PRFS was 92%, 86%, 79%, and 67%, respectively, for patients with PSA nadir values of 0-0.49, 0.5-0.99, 1.0-1.99, and >2.0 ng/mL (p < 0.001). Among patients free of biochemical relapse at 8 years, the median nadir level was 0.1 ng/mL, and 90% of these patients achieved a nadir PSA level <0.6 ng/mL. CONCLUSIONS: Outcome after permanent BT for prostatic cancer relates to tumor stage, Gleason score, pretreatment PSA, BT year, and post-BT dosimetric quality. PSA nadir < or =0.5 ng/mL was particularly associated with durable long-term PSA disease-free survival. The only controllable factor to impact on long-term outcome was the D90 which is a reflection of implant quality.

Brachytherapy↗
PubMed2006

Dosimetric comparison of four target alignment methods for prostate cancer radiotherapy.

PURPOSE: The aim of this study was to compare the dosimetric consequences of 4 treatment delivery techniques for prostate cancer patients treated with intensity-modulated radiotherapy (IMRT). METHODS AND MATERIALS: During an 8-week course of radiotherapy, 10 patients underwent computed tomography (CT) scans 3 times per week (243 total) before daily treatment with a CT-linear accelerator. Treatment delivery was simulated by realigning a fixed-margin treatment plan on each CT scan and calculating doses. The alignment methods were those based on the following: skin marks, bony registration, ultrasonography (US), and in-room CT. For the last two methods, prostate was the alignment target. The dosimetric effects of these alignment methods on the prostate, seminal vesicles, rectum, and bladder were compared. The average daily minimum dose to 0.1 cm3 was used as the metric for target coverage. RESULTS: Skin and bone alignments provided acceptable prostate coverage for only 70% of patients, US alignment for 90%, and CT alignment for 100%. CT-based alignment of the prostate provided seminal vesicle (SV) coverage of > or = 69 Gy for all patients; US and bone alignments provided SV coverage of > or = 60 Gy. This SV coverage may be acceptable for early-stage cancer (equivalent SV dose = 55.8 Gy at 1.8 Gy per fraction), but unacceptable for late-stage cancer (SV dose = 75.6 Gy). At 75.6 Gy, the acceptable rate for SV coverage was 40% for skin and bone alignments, 70% for US, and 80% for CT. CONCLUSIONS: Direct target alignment methods (US and CT) provided better target coverage. CT-guided alignment provided the best and most consistent dosimetric coverage. A larger planning target volume margin is needed for SV coverage when the alignment target is the prostate.

Algorithms↗
PubMed2006

Biochemical and clinical significance of the posttreatment prostate-specific antigen bounce for prostate cancer patients treated with external beam radiation therapy alone: a multiinstitutional pooled analysis.

BACKGROUND: The posttreatment prostate-specific antigen (PSA) bounce phenomenon has been recognized in at least 20% of all patients treated with radiation. The purpose of the current report was to determine if there was a difference in biochemical and clinical control between the bounce and nonbounce (NB) patients using pooled data on 4839 patients with T1-2 prostate cancer treated with external beam radiation therapy (RT) alone at 9 institutions between 1986 and 1995. METHODS: The median follow-up was 6.3 years. A posttreatment PSA bounce was defined by a minimal rise of 0.4 ng/mL over a 6-month follow-up period, followed by a drop in PSA level of any magnitude. Endpoints included no biochemical evidence of disease (bNED) failure (BF) (ASTRO definition), distant failure (DF), cause-specific failure (CSF), and overall survival (OS). Patients were stratified by pretreatment PSA, Gleason score, T stage, age, dose, and risk group. RESULTS: In all, 978 (20%) patients experienced at least 1 posttreatment PSA bounce. Within 3 subgroups (risk group, pretreatment PSA, and age), statistically significant differences of remaining bounce-free were observed on univariate analysis. Patients < 70 years had a 72% chance of remaining bounce-free at 5 years compared with 75% for older patients (P = .04). The NB patients had 72% bNED control at 10 years compared with 58% for the bounce patients. The effect of a bounce remained statistically significant on multivariate analysis (P < .0001). No statistically significant difference in DF, CSF, or OS was observed. CONCLUSIONS: Patients treated with external beam radiation therapy alone who experience a posttreatment PSA bounce have increased risk of BF. However, this did not translate into a difference in clinical failure with the available follow-up in the current study.

Adult↗
PubMed2006

Influence of obesity on biochemical and clinical failure after external-beam radiotherapy for localized prostate cancer.

BACKGROUND: Several reports have shown that obesity is associated with increased risk of biochemical failure after radical prostatectomy. However, limited information is available regarding the impact of obesity on prostate cancer progression after radiotherapy. The current study sought to determine whether obesity was an independent predictor of biochemical failure (BF) and clinical recurrence (CF) among patients treated with external-beam radiotherapy (EBRT). METHODS: A retrospective analysis was performed on 873 patients receiving EBRT as the sole treatment for localized prostate cancer between 1988 and 2001. The Kaplan-Meier method, log-rank test, and Cox proportional hazards analyses were performed. RESULTS: Of the 873 patients, 18% were mildly obese and 5% were moderately to severely obese. Obesity was related to younger age at diagnosis (P < .001), more recent year of diagnosis (P = .03), and race (P = .03), with African-American men having the highest obesity rates. During a mean follow-up of 96 months, 295 patients experienced BF and 127 had CF. On multivariate analysis, controlling for clinical and treatment characteristics, increased body mass index (BMI) significantly predicted BF (hazards ratio [HR] = 1.04; 95% confidence interval [95% CI], 1.02-1.07) with a positive trend by BMI category (P = .001). Similar results were found when the outcome was CF; BMI remained an independent predictor of progression (HR = 1.05; 95% CI, 1.01-1.09), with a statistically significant trend by increased BMI category (P = .03). CONCLUSIONS: The current findings validate the important role of obesity, not only on BF but also on CF, and suggest a link to the biologic basis of tumor progression that can be therapeutically exploited.

Adult↗
PubMed2006

First-year PSA kinetics and minima after prostate cancer radiotherapy are predictive of overall survival.

PURPOSE: We analyzed whether first-year prostate-specific antigen (PSA) kinetics and minima are predictive of overall survival (OS). METHODS AND MATERIALS: The data set contained 1,174 patients treated with external beam radiotherapy (RT) from 1987 to 2001. The relative rate of change (lambda) in post-RT PSA values during the first year (13.5 months) was computed using regression analysis of ln(PSA) vs. time. We also computed the PSA minimum (mPSA) reached during the same period. Recursive partitioning analysis was used to identify the relevant cutpoints for the factors being investigated for its association with survival: age, pretreatment PSA, radiation dose, relative rate of change in PSA post-RT, and 1-year PSA minimum. For each of the other factors stage, Gleason score and risk group, all possible cutpoints were considered in the multivariate analyses. Significant factors were considered in the multivariate analyses to identify independent predictors for overall survival. RESULTS: The median value of lambda was -1.0 years(-1) (range, -11.0-5.1 years(-1)). The 1-year minimum had a median of 0.8 ng/mL (range, 0.01-30.9 ng/mL). Recursive partitioning analysis and Cox proportional hazards analyses identified the following pretreatment or treatment factors adversely related to OS: age, Gleason score, stage, and dose. First-year mPSA > or = 4 ng/mL and lambda > 0 were post-RT independent prognostic factors for worse OS. CONCLUSION: First-year post-RT PSA kinetics and minima are early response parameters predictive of overall survival for prostate cancer patients. These factors may be useful in selecting patients for early salvage therapy.

Adult↗
PubMed2006

Increasing external beam dose for T1-T2 prostate cancer: effect on risk groups.

PURPOSE: The aim of this study was to investigate effect of increasing dose on risk groups for clinical failure (CF: local failure or distant failure or hormone ablation or PSA>or=25 ng/ml) in patients with T1-T2 prostate cancer treated with external beam radiotherapy. METHODS AND MATERIALS: Patients (n=4,537) were partitioned into nonoverlapping dose ranges, each narrow enough that dose was not a predictor of CF, and risk groups for CF were determined using recursive partitioning analysis (RPA). The same technique was applied to the highest of these dose ranges (70-76 Gy, 1,136 patients) to compare risk groups for CF in this dose range with the conventional risk-group classification. RESULTS: Cutpoints defining low-risk groups in each dose range shifted to higher initial PSA levels and Gleason scores with increasing dose. Risk groups for CF in the dose range 70-76 Gy were not consistent with conventional risk groups. CONCLUSIONS: The conventional classification of risk groups was derived in the early PSA era, when total doses<70 Gy were common, and it is inconsistent with risk groups for patients treated to doses>70 Gy. Risk-group classifications must be continuously re-examined whenever the trend is toward increasing total dose.

Humans↗
PubMed2006

Comparison of biochemical failure definitions for permanent prostate brachytherapy.

PURPOSE: To assess prostate-specific antigen (PSA) failure definitions for patients with Stage T1-T2 prostate cancer treated by permanent prostate brachytherapy. METHODS AND MATERIALS: A total of 2,693 patients treated with radioisotopic implant as solitary treatment for T1-T2 prostatic adenocarcinoma were studied. All patients had a pretreatment PSA, were treated at least 5 years before analysis, 1988 to 1998, and did not receive hormonal therapy before recurrence. Multiple PSA failure definitions were tested for their ability to predict clinical failure. RESULTS: Definitions which determined failure by a certain increment of PSA rise above the lowest PSA level to date (nadir + x ng/mL) were more sensitive and specific than failure definitions based on PSA doubling time or a certain number of PSA rises. The sensitivity and specificity for the nadir + 2 definition were 72% and 83%, vs. 51% and 81% for 3 PSA rises. The surgical type definitions (PSA exceeding an absolute value) could match this sensitivity and specificity but only when failure was defined as exceeding a PSA level in the 1-3 ng/mL range and only when patients were allowed adequate time to nadir. When failure definitions were compared by time varying covariate regression analysis, nadir + 2 ng/mL retained the best fit. CONCLUSIONS: For patients treated by permanent radioisotopic implant for prostate cancer, the definition nadir + 2 ng/mL provides the best surrogate for failure throughout the entire follow-up period, similar to patients treated by external beam radiotherapy. Therefore, the same PSA failure definition could be used for both modalities. For brachytherapy patients with long-term follow-up, at least 6 years, defining failure as exceeding an absolute PSA level in the 0.5 ng/mL range may be reasonable.

Adenocarcinoma↗
PubMed2005

PSA nadir predicts biochemical and distant failures after external beam radiotherapy for prostate cancer: a multi-institutional analysis.

PURPOSE: To determine the significance of prostate-specific antigen (PSA) nadir (nPSA) and the time to nPSA (T(nPSA)) in predicting biochemical or clinical disease-free survival (PSA-DFS) and distant metastasis-free survival (DMFS) in patients treated with definitive external beam radiotherapy (RT) for clinical Stage T1b-T2 prostate cancer. METHODS AND MATERIALS: Nine participating institutions submitted data on 4839 patients treated between 1986 and 1995 for Stage T1b-T2cN0-NxM0 prostate cancer. All patients were treated definitively with RT alone to doses > or =60 Gy, without neoadjuvant or planned adjuvant androgen suppression. A total of 4833 patients with a median follow-up of 6.3 years met the criteria for analysis. Two endpoints were considered: (1) PSA-DFS, defined as freedom from PSA failure (American Society for Therapeutic Radiology and Oncology definition), initiation of androgen suppression after completion of RT, or documented local or distant failure; and (2) DMFS, defined as freedom from clinically apparent distant failure. In patients with failure, nPSA was defined as the lowest PSA measurement before any failure. In patients without failure, nPSA was the lowest PSA measurement during the entire follow-up period. T(nPSA) was calculated from the completion of RT to the nPSA date. RESULTS: A greater nPSA level and shorter T(nPSA) were associated with decreased PSA-DFS and DMFS in all patients and in all risk categories (low [Stage T1b, T1c, or T2a, Gleason score < or =6, and PSA level < or =10 ng/mL], intermediate [Stage T1b, T1c, or T2a, Gleason score < or =6, and PSA level >10 but < or =20 ng/mL, or Stage T2b or T2c, Gleason score < or =6, and PSA level < or =20 ng/mL, or Gleason score 7 and PSA level < or =20 ng/mL], and high [Gleason score 8-10 or PSA level >20 ng/mL]), regardless of RT dose. The 8-year PSA-DFS and DMFS rate for patients with nPSA <0.5 ng/mL was 75% and 97%; nPSA > or =0.5 but <1.0 ng/mL, 52% and 96%; nPSA > or =1.0 but <2.0 ng/mL, 40% and 91%; and nPSA > or =2.0 ng/mL, 17% and 73%, respectively. The 8-year PSA-DFS and DMFS rate for patients with T(nPSA) <6 months was 27% and 66%; T(nPSA) > or =6 but <12 months, 31% and 85%; T(nPSA) > or =12 but <24 months, 42% and 94%; and T(nPSA) > or =24 months, 75% and 99%, respectively. A shorter T(nPSA) was associated with decreased PSA-DFS and DMFS, regardless of the nPSA. Both nPSA and T(nPSA) were significant predictors of PSA-DFS and DMFS in multivariate models incorporating clinical stage, Gleason score, initial PSA level, and RT dose. The significance of nPSA and T(nPSA) was supported by landmark analysis, as well as by analysis of nPSA and T(nPSA) as time-dependent covariates. A dose > or =70 Gy was associated with a lower nPSA level and longer T(nPSA) in all risk categories, and a greater dose was significantly associated with greater PSA-DFS and DMFS in multivariate analysis. Regression analysis confirmed that higher clinical stage, Gleason score, and initial PSA were associated with a greater nPSA level. CONCLUSION: The results of this large, multi-institutional analysis of 4833 patients have provided important evidence that nPSA and T(nPSA) after definitive external beam RT are not only predictive of a predominantly PSA endpoint (PSA-DFS), but are also predictive of distant metastasis in all clinical risk categories. Greater RT doses were associated with lower nPSA, longer T(nPSA), and improved PSA-DFS and DMFS.

Disease-Free Survival↗
PubMed2005

Increased risk of biochemical and local failure in patients with distended rectum on the planning CT for prostate cancer radiotherapy.

PURPOSE: To retrospectively test the hypothesis that rectal distension on the planning computed tomography (CT) scan is associated with an increased risk of biochemical and local failure among patients irradiated for prostate carcinoma when a daily repositioning technique based on direct prostate-organ localization is not used. METHODS AND MATERIALS: This study included 127 patients who received definitive three-dimensional conformal radiotherapy for prostate cancer to a total dose of 78 Gy at The University of Texas M. D. Anderson Cancer Center. Rectal distension was assessed by calculation of the average cross-sectional rectal area (CSA; defined as the rectal volume divided by length) and measuring three rectal diameters on the planning CT. The impact of rectal distension on biochemical control, 2-year prostate biopsy results, and incidence of Grade 2 or greater late rectal bleeding was assessed. RESULTS: The incidence of biochemical failure was significantly higher among patients with distended rectums (CSA >11.2 cm(2)) on the planning CT scan (p = 0.0009, log-rank test). Multivariate analysis indicates that rectal distension and high-risk disease are independent risk factors for biochemical failure, with hazard ratios of 3.89 (95% C.I. 1.58 to 9.56, p = 0.003) and 2.45 (95% C.I. 1.18 to 5.08, p = 0.016), respectively. The probability of residual tumor without evidence of radiation treatment (as scored by the pathologist) increased significantly with rectal distension (p = 0.010, logistic analysis), and a lower incidence of Grade 2 or greater late rectal bleeding within 2 years was simultaneously observed with higher CSA values (p = 0.031, logistic analysis). CONCLUSIONS: We found strong evidence that rectal distension on the treatment-planning CT scan decreased the probability of biochemical control, local control, and rectal toxicity in patients who were treated without daily image-guided prostate localization, presumably because of geographic misses. Therefore, an empty rectum is warranted at the time of simulation. These results also emphasize the need for image-guided radiotherapy to improve local control in irradiating prostate cancer.

Aged↗
PubMed2005

Out-of-field photon and neutron dose equivalents from step-and-shoot intensity-modulated radiation therapy.

PURPOSE: To measure the photon and neutron out-of-treatment-field dose equivalents to various organs from different treatment strategies (conventional vs. intensity-modulated radiation therapy [IMRT]) at different treatment energies and delivered by different accelerators. METHODS AND MATERIALS: Independent measurements were made of the photon and neutron out-of-field dose equivalents resulting from one conventional and six IMRT treatments for prostate cancer. The conventional treatment used an 18-MV beam from a Clinac 2100; the IMRT treatments used 6-MV, 10-MV, 15-MV, and 18-MV beams from a Varian Clinac 2100 accelerator and 6-MV and 15-MV beams from a Siemens Primus accelerator. Photon doses were measured with thermoluminescent dosimeters in a Rando phantom, and neutron fluence was measured with gold foils. Dose equivalents to the colon, liver, stomach, lung, esophagus, thyroid, and active bone marrow were determined for each treatment approach. RESULTS: For each treatment approach, the relationship between dose equivalent per MU, distance from the treatment field, and depth in the patient was examined. Photon dose equivalents decreased approximately exponentially with distance from the treatment field. Neutron dose equivalents were independent of distance from the treatment field and decreased with increasing tissue depth. Neutrons were a significant contributor to the out-of field dose equivalent for beam energies > or =15 MV. CONCLUSIONS: Out-of-field photon and neutron dose equivalents can be estimated to any point in a patient undergoing a similar treatment approach from the distance of that point to the central axis and from the tissue depth. This information is useful in determining the dose to critical structures and in evaluating the risk of associated carcinogenesis.

Algorithms↗
PubMed2005

The calculated risk of fatal secondary malignancies from intensity-modulated radiation therapy.

PURPOSE: Out-of-field radiation doses to normal tissues may be associated with an increased risk of secondary malignancies, particularly in long-term survivors. Step-and-shoot intensity-modulated radiation therapy (IMRT), an increasingly popular treatment modality, yields higher out-of-field doses than do conventional treatments, because of an increase in required monitor units (beam-on time). METHODS: We used published risk coefficients (NRCP Report 116) and out-of-field dose equivalents to multiple organ sites to estimate a conservative maximal risk of fatal secondary malignancy associated with 6 IMRT approaches and 1 conventional external-beam approach for prostate cancer. RESULTS: Depending on treatment energy, the IMRT treatments required 3.5-4.9 times as many monitor units to deliver as did the conventional treatment. The conservative maximum risk of fatal second malignancy was 1.7% for conventional radiation, 2.1% for IMRT using 10-MV X-rays, and 5.1% for IMRT using 18-MV X-rays. Intermediate risks were associated with IMRT using 6-MV X-rays: 2.9% for treatment with the Varian accelerator and 3.7% for treatment with the Siemens accelerator, as well as using 15-MV X-rays: 3.4% (Varian) and 4.0% (Siemens). CONCLUSION: The risk of fatal secondary malignancy differed substantially between IMRT and conventional radiation therapy for prostate cancer, as well as between different IMRT approaches. Perhaps this risk should be considered when choosing the optimal treatment technique and delivery system for patients who will undergo prostate radiation.

Dose-Response Relationship, Radiation↗
PubMed2005

Validation of an accelerated 'demons' algorithm for deformable image registration in radiation therapy.

A greyscale-based fully automatic deformable image registration algorithm, originally known as the 'demons' algorithm, was implemented for CT image-guided radiotherapy. We accelerated the algorithm by introducing an 'active force' along with an adaptive force strength adjustment during the iterative process. These improvements led to a 40% speed improvement over the original algorithm and a high tolerance of large organ deformations. We used three methods to evaluate the accuracy of the algorithm. First, we created a set of mathematical transformations for a series of patient's CT images. This provides a 'ground truth' solution for quantitatively validating the deformable image registration algorithm. Second, we used a physically deformable pelvic phantom, which can measure deformed objects under different conditions. The results of these two tests allowed us to quantify the accuracy of the deformable registration. Validation results showed that more than 96% of the voxels were within 2 mm of their intended shifts for a prostate and a head-and-neck patient case. The mean errors and standard deviations were 0.5 mm+/-1.5 mm and 0.2 mm+/-0.6 mm, respectively. Using the deformable pelvis phantom, the result showed a tracking accuracy of better than 1.5 mm for 23 seeds implanted in a phantom prostate that was deformed by inflation of a rectal balloon. Third, physician-drawn contours outlining the tumour volumes and certain anatomical structures in the original CT images were deformed along with the CT images acquired during subsequent treatments or during a different respiratory phase for a lung cancer case. Visual inspection of the positions and shapes of these deformed contours agreed well with human judgment. Together, these results suggest that the accelerated demons algorithm has significant potential for delineating and tracking doses in targets and critical structures during CT-guided radiotherapy.

Algorithms↗
PubMed2005

Symptomatic local recurrence of prostate carcinoma after radiation therapy.

BACKGROUND: Symptomatic local recurrence of prostate carcinoma (SLRPC) after radiation therapy (RT) is associated with morbidity and debilitating symptoms that have a substantial impact on the patient's quality of life. Most reports on the results of RT for localized prostate carcinoma (PC) do not address this endpoint. The objective of this study was to determine the incidence of SLRPC and to identify the risk factors for this endpoint. METHODS: The medical charts of 1006 patients who received RT for localized PC at the University of Texas M. D. Anderson Cancer Center between 1987 and 1997 were reviewed. Local symptoms were defined as hematuria, voiding symptoms, urinary obstruction, and pelvic pain. Progressive symptoms accompanied by either confirmatory histology or cystoscopic findings were attributed to PC. Univariate and multivariate analyses using Cox proportional hazards models were applied to identify risk predictors. RESULTS: Among 964 patients for whom follow-up data were available, 277 patients had prostate-specific antigen (PSA) progression, and 45 patients died of PC during a median follow-up of 9.4 years. In total, 33 patients (3.4%) developed SLRPC. In patients who experienced biochemical progression, the actuarial 5-year incidence of SLRPC was 8.3%. Among the patients who had developed SLRPC, 23 patients (69.7%) died of PC at a median of 25.3 months from the onset of local symptoms. Adverse histologic tumor subtypes (ductal, small cell, and sarcomatoid) were associated significantly with SLRPC (hazard ratio, 8.4; 95% confidence interval, 2.99-23.63). Clinical T classification at diagnosis, Gleason score, and initial PSA level showed a trend toward an increased hazard ratio. CONCLUSIONS: SLRPC after radiotherapy therapy was an uncommon but clinically significant event. Aggressive histologic subtypes were predictive of this endpoint. Clinical T classification, Gleason score, and initial prostate-specific antigen levels also may have predictive value.

Aged↗
PubMed2005

Implementation and validation of a three-dimensional deformable registration algorithm for targeted prostate cancer radiotherapy.

PURPOSE: Daily prostate deformation hinders accurate calculation of dose, especially to intraprostatic targets. We implemented a three-dimensional deformable registration algorithm to aid dose tracking for targeted prostate radiotherapy. METHODS AND MATERIALS: The algorithm registers two computed tomography (CT) scans by iteratively minimizing their differences in image intensity. For validation, we measured the accuracy in registering (a) a pelvic CT set to its mathematically deformed counterpart, (b) CT scans of a deformable pelvic phantom with and without an endorectal balloon inflated, to simulate intraprostatic targets, 23 CT-opaque seeds were embedded in the prostate, and (c) two pelvic CT scans of a patient obtained on 2 separate days. RESULTS: The mean (SD) error in registering the pelvic CT set to its transformed set was 0.5 mm (1.5), with correlation coefficient improvement from 0.626 to 0.991. Using the deformable pelvic phantom, the correlation coefficient improved from 0.543 to 0.816 after registration. The mean (SD) error in tracking the intraprostatic seeds was 0.8 mm (0.5). The correlation coefficient improved from 0.610 to 0.944 after registration of the two patient CT sets. CONCLUSION: The algorithm had an accuracy of about 1 mm. It could be used for optimizing dose calculation and delivery for prostate radiotherapy.

Algorithms↗
PubMed2005

Assessing the impact of an alternative biochemical failure definition on radiation dose response for high-risk prostate cancer treated with external beam radiotherapy.

PURPOSE: The American Society for Therapeutic Radiology and Oncology (ASTRO) biochemical failure definition has recently been compared with various alternative definitions. We assessed the effect of using an alternative failure definition on the dose-response characteristics of high-risk prostate cancer treated with radiotherapy alone. METHODS AND MATERIALS: This study included 363 high-risk prostate cancer patients treated with external beam radiotherapy alone from 1987 to 1999. These patients have one or more of the following: 1992 American Joint Committee on Cancer (AJCC) digital rectal examination (DRE) stage > or = cT3, prostate-specific antigen (PSA) > 20 ng/mL, and/or biopsy Gleason score > or = 8. We previously reported the dose response based on the ASTRO definition for these patients. In this study, a biochemical failure is defined as a PSA rise > or = 2 ng/mL above the current nadir PSA (CN + 2). The failure date is defined as the time at which the event occurred (i.e., the call date). RESULTS: Using CN + 2, the tumor control probability (TCP) continues to decrease with time as opposed to reaching a plateau as with the ASTRO definition. At 5 years, TCD50 (95% CI), the dose to achieve 50% tumor control, for high-risk prostate cancer, is 70.4 (68.0-72.9) Gy using CN + 2 [ASTRO: 75.5 (70.7-80.2) Gy]. The relative slope, gamma50 (95% CI) is 1.8 (0.8-2.8) [ASTRO: 1.7 (0.7-2.7)]. Recursive partitioning again identified two subgroups: PSA < vs. > or = 13 ng/mL (ASTRO: PSA < or = vs. > 20 ng/mL). The difference in TCD50 between the two subgroups is about 20 Gy at 5 years (ASTRO: about 15 Gy at 5 years). CONCLUSION: This analysis using the CN + 2 failure definition continues to show a dose response for the high-risk group of patients. However, the dose-response characteristics differ from those estimated using the ASTRO definition. We observed that the position (TCD50) and steepness (gamma50) of the dose-response curve changed with time as long as the TCP continued to decrease. This suggests that the dose response characteristics derived from data with longer follow-up may be different from those derived with shorter follow-up using the CN + 2 or similar failure definitions which do not back-date the failure. These changes in dose-response characteristics as well as the time dependence of dose response should be noted when investigators design dose escalation trials for the high-risk prostate cancer patients.

Adenocarcinoma↗