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Biomedical subjects

A T Porter

Publications and source records attributed to A T Porter.

At least 91 records · Page 5Linked to original sources
PubMed1993

Frequency of residual neoplasm in the prostate following three-dimensional conformal radiotherapy.

The incidence of residual neoplastic cells on prostatic biopsy following conventional external beam radiotherapy is reported to range from 40-90%. As a result, it has been stated that current modalities of radiotherapy may carry an unacceptable local failure rate even in patients irradiated for low stage disease. In order to assess the potential benefits of three-dimensional (3-D) treatment planning, an unselected, consecutive group of patients with localized adenocarcinoma of the prostate was evaluated. This study was designed to determine the frequency of residual cancer in the prostate two years following definitive external beam radiotherapy designed, using a 3-D planning system. Between February 1988 and February 1989, 30 consecutive patients with localized (Stage T1-T3NxMo) adenocarcinoma of the prostate received definitive external beam radiotherapy. All treatment fields were designed with a computed tomography (CT)-based 3-D treatment planning system, resulting in a static conformal radiotherapy plan. The minimum dose delivered to the target volume, which included the prostate, periprostatic tissues, and a 1 cm margin, was between 65 and 69 cGy. Twenty-six patients had Stage T1, T2NxMo primary tumors and four were T3NxMo. Two years following the completion of treatment, all patients underwent digital rectal examination, transrectal ultrasound examination of the prostate with multiple biopsies, bone scan, and serum prostate specific antigen (PSA) determinations. Residual prostate cancer was proven by biopsy in six of 30 patients (20%). Four of 26 (15%) with Stage T1 and T2 tumors had a positive biopsy. However, two of the four Stage T3 tumors had postradiation biopsies positive for cancer (50%). Only one patient with a positive biopsy had an abnormal rectal examination. Five of the eight patients with elevated serum PSA levels after two years had residual neoplasia identified on biopsy. One of six patients with an abnormal postradiation ultrasound had residual tumor. Only one of the 22 patients (5%) with a normal serum PSA at two years had a positive postradiation biopsy. In patients with localized prostate cancer, the use of 3-D static conformal radiotherapy followed by multiple ultrasound guided biopsies confirmed the efficacy of external beam radiotherapy in low stage disease. We believe that the low incidence of positive biopsies in this study resulted from the benefits of 3-D treatment planning as well as the fact that all patients were evaluated, whereas past studies have been in selected patient groups when suspicion of residual disease existed prior to biopsy.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenocarcinoma↗
PubMed1993

Preliminary results of a hyperfractionated dose escalation study for locally advanced adenocarcinoma of the prostate.

The objective of this study was to build on our experience with 3-D conformal radiotherapy (CRT) by using a hyperfractionated dose escalation scheme to maximize the therapeutic ratio between improved local control and reduced morbidity in patients with locally advanced prostate cancer. Twenty patients with locally advanced (T3, T4) adenocarcinoma of the prostate were treated with a hyperfractionated radiotherapy schedule. All fields were designed with a conformal therapy based beam's eye view, 3-D planning system. The pelvic lymph nodes received 1.8 Gy/day to a total dose of 45 Gy in 5 weeks. Using partial transmission blocks, the prostate and periprostatic tissues received 1.3 Gy twice daily (minimum interval of 6 h) to a total dose of 78 Gy in 6 weeks. The dose was chosen by calculating the biologically effective dose (BED) which would produce the same effect in late reacting tissue but an increase for the tumor as our standard dose of 69 Gy delivered in 1.8-2.0 Gy fractions. The alpha/beta chosen for late damage was 3 Gy and 10 Gy was used for the tumor. All 20 patients completed the planned course of treatment. Although an increase in the tumor BED would be expected to result in increased acute effects, no significant worsening of acute side-effects was observed compared with standard treatment. All patients had only mild (Grade 1) rectal or bladder toxicity during treatment. One patient had an exacerbation of diverticulitis during treatment requiring hospitalization for antibiotics but completed treatment on schedule.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1993

Strontium 89 therapy and relief of pain in patients with prostatic carcinoma metastatic to bone: a dose response relationship?

Reports published in the English literature of clinical trials utilizing intravenous strontium 89 (89Sr) in the treatment of patients with prostatic adenocarcinoma metastatic to bone were reviewed. Correlation coefficients were calculated for increasing dose of 89Sr and complete pain relief and complete and partial pain relief. Statistically significant positive correlations were obtained for complete relief of pain. Positive correlations were also found between those patients who had at least partial pain relief (defined as at least a 50% reduction in analgesia requirement), but these did not reach significance. This analysis suggests that a dose response relationship may exist between the dosage of 89Sr administered, and complete relief of pain due to skeletal metastases. The optimal dosage of 89Sr in this clinical situation has not been established, and prospective, carefully executed and analyzed randomized trials will be required to test whether and to what extent dose intensity of 89Sr determines outcome independently of other factors.

Adenocarcinoma↗
PubMed1993

Advantages of CT and beam's eye view display to confirm the accuracy of pelvic lymph node irradiation in carcinoma of the prostate.

Possible advantages of computed tomography (CT) and beam's eye view (BEV) display in the design of pelvic irradiation fields were studied in 20 consecutive patients with localized adenocarcinoma of the prostate. Pelvic fields were designed with standard four-field techniques. Then, CT and BEV display were done to define the reduced prostate tumor volumes. With treatment-planning CT, the location of the pelvic vascular structures (internal and external iliac artery and vein) was outlined. These were used as an approximation of the location of the lymph nodes. A BEV display of these lymph node volumes was then compared with the pelvic fields designed without CT and BEV display. Nineteen of the 20 patients had part of the CT-defined lymph node volume (a portion of the internal iliac lymph node volume) excluded from the original field design. Thirteen patients also had part of the external iliac nodal volume excluded. Dose-volume histograms showed that up to 30% of the lymph node volume received only 56% of the prescribed dose.

Adenocarcinoma↗
PubMed1993

Perspectives on the role of radiotherapy in organ-confined and locally advanced prostate cancer.

Radiotherapy is an effective management option in the treatment of organ-confined prostate cancer with survival results and local control possibilities similar to those of surgery. Although radiotherapy is used in locally advanced (stage-C) prostate cancer, there are significant developments that may make treatment more effective, such as hormonal cytoreduction, neutron radiotherapy and conformal therapy.

Humans↗
PubMed1993

Workshop summary: approaches to radical prostatectomy.

The retropubic approach has recently become the method of choice for radical prostatectomy. This has been particularly evident since the 1970s, when open staging lymphadenectomy became an important part of the diagnostic workup, as both procedures could be carried out concurrently via the anterior approach. However, the development and rapidly increasing use of laparoscopic lymphadenectomy may signal a return to the perineal approach in certain cases. Alternatives to radical prostatectomy, including radiotherapy and interstitial brachytherapy, may also have their place. The audience was asked to comment on their own practices and the factors that would influence their decisions.

Aged↗
PubMed1993

Strontium-89 as an adjuvant to external beam radiation improves pain relief and delays disease progression in advanced prostate cancer: results of a randomized controlled trial.

In a multicenter, randomized controlled trial involving 126 patients with endocrine-resistant advanced prostate cancer, all of whom received external beam radiotherapy, additional treatment with a single injected dose of 400 MBq strontium-89 (Metastron) significantly improved overall pain control. Adjuvant therapy with strontium-89 also significantly reduced analgesia requirements compared with placebo and delayed disease progression, as indicated by the requirement for further external beam radiotherapy. On certain measures, patients receiving strontium-89 also showed enhanced quality of life. Accompanying these changes, levels of prostate tumor markers were significantly reduced by strontium-89 treatment. The benefits resulting from adjuvant strontium therapy were associated with tolerable hematologic toxicity. The addition of strontium-89 to external beam radiation had no effect on survival. However, it has clear implications for improved palliation in advanced prostate cancer and may also impact positively on treatment costs.

Aged↗
PubMed1992

Daily monitoring and correction of radiation field placement using a video-based portal imaging system: a pilot study.

We have developed a video-based portal imaging system for radiotherapy localization. The system can acquire high quality portal images automatically using short (1-3 monitor unit) irradiations and immediately display the images. The major advantage of the imaging system is that it can be used routinely to check and correct patient positioning before much of the daily irradiation has been delivered. The portal imaging system has been used in a pilot study to monitor five patients during each of their daily treatments. The study has shown that: (i) image quality is sufficiently high to detect discrepancies in field placement from that prescribed on the simulator film; (ii) discrepancies in field placement occur frequently; and, (iii) routine correction of patient and block positioning can reduce the size of these discrepancies. This is the first time that field placement in radiation therapy has been checked and corrected routinely, before the treatment irradiation. However, limitations in the size of the field of view and in the methods of extracting and presenting the geometric information to the users limits the clinical utility of the imaging system. Solutions to these limitations are currently under development.

Computer Terminals↗
PubMed1992

Dose estimation in strontium-89 radiotherapy of metastatic prostatic carcinoma.

Strontium-89 radiotherapy is becoming an important treatment in the palliation of bone pain from osteoblastic metastases. The absorbed dose delivered to bone metastases during 89Sr radiotherapy has been estimated in four patients with metastatic prostatic carcinoma. Patients were injected with a tracer dose of 85Sr-chloride. Blood and urine samples were obtained during the week following injection. Strontium-85 scintigrams of metastases and normal bone were obtained up to 8 wk postinjection. Half of the patients showed elevated whole-body retention; plasma-strontium concentrations were decreased from normal values. Uptake of strontium in metastases was 2-25 times that in normal bone but rates of washout of strontium from metastases were similar to those from normal bone. Absorbed doses delivered in infinite time to the metastases by 89Sr ranged from 21 +/- 4 to 231 +/- 56 cGy/MBq with a median value of 68 cGy/MBq. Doses to red marrow were less by a factor of 2 to 50. These absorbed doses are sufficiently large to be expected to produce a therapeutic benefit.

Bone Neoplasms↗
PubMed1992

Strontium-89 and low-dose infusion cisplatin for patients with hormone refractory prostate carcinoma metastatic to bone: a preliminary report.

Strontium-89 has been used for the treatment of painful bony metastases in patients suffering from disseminated adenocarcinoma of the prostate, with a variable proportion of patients obtaining clinically significant reductions in analgesic requirements. Based on data revealing enhancement of continuous low-dose rate irradiation by low-dose cisplatin in murine models, a protocol using 148 MBq (4 mCi) of 89Sr and 35 mg/m2 of cisplatin infused over 2 days, 1 and 4 wk after administration of the radioisotope was undertaken. Preliminary data suggest good pain relief with 55% of 18 patients entered thus far obtaining at least a 50% reduction in analgesic requirements. Improvements in total alkaline phosphatase and serum lactate dehydrogenase have consistently been seen, with some patients exhibiting improvements in hemoglobin, tumor markers and bone scans. Toxicity appears to be mild, with no life-threatening complications. In particular, myelosuppression after one course of treatment was modest, but retreatments in two patients has resulted in grade 3 hematologic toxicity. Two patients developed a "pain flare" after administration of cisplatin. Further accrual to this study will allow more accurate determination of pain response rate, and improved evaluation of parameters of objective response.

Adenocarcinoma↗
PubMed1991

A prospective, randomised double-blind crossover study to examine the efficacy of strontium-89 in pain palliation in patients with advanced prostate cancer metastatic to bone.

The palliative efficacy of strontium-89 chloride has been evaluated in a prospective double-blind crossover study comparing it with stable strontium as placebo in 32 patients with prostate cancer metastatic to bone. Response was assessed 5 weeks after each treatment. 26 patients were evaluable. Complete pain relief was only reported following strontium-89 injection. Statistical comparison between placebo and strontium-89 showed clear evidence of a therapeutic response to strontium-89 compared with only a limited placebo effect (P less than 0.01).

Aged↗
PubMed1991

Acute non-lymphocytic leukaemia and myelofibrosis following sequential hemibody irradiation for prostatic carcinoma.

Sequential hemibody radiotherapy (SHBI) is currently being evaluated in clinical trials as adjuvant treatment in cancer patients who are potential long-term survivors. The potential late adverse effects of this therapeutic modality on the bone marrow may place patients at risk for the complications of aplasia, leukaemia, and myeloproliferative syndromes. We describe a case of acute non-lymphocytic leukaemia and myelofibrosis following SHBI for prostate carcinoma. The possible role of radiation in the induction of these abnormalities is discussed.

Adenocarcinoma↗
PubMed1991

Iridium-192 brachytherapy in the treatment of cancer of the prostate.

Aggressive radiotherapy was used in 170 patients with advanced localized carcinoma of the prostate. After pelvic lymphadenectomy, 192Ir brachytherapy was used to deliver 3500 cGy to the prostate within 2 days. External-beam therapy (4500 cGy) was then given to a total of 8000 cGy. Random biopsies 18 months afterward were negative for residual cancer in 62 of 83 patients (75%), and 37 of 45 patients (82%) with pathologically proved localized disease remain without evidence of disease. Morbidity was significantly reduced in the most recent 70 patients by improvements in technique. The authors believe such therapy should be considered for patients with advanced stage B2 or C disease in particular.

Adenocarcinoma↗
PubMed1990

Prostate-specific antigen. Monitoring the response of carcinoma of the prostate to radiotherapy with a new tumor marker.

The role of prostate-specific antigen (PSA), a sensitive tumor marker for cancer of the prostate, has yet to be defined in patients treated with radiotherapy. To evaluate this, PSA and acid phosphatase (AP) were measured prospectively in 110 sequential patients who presented with locoregional carcinoma of the prostate and in whom radiotherapy was to be definitive treatment. Therapy was divided into the following treatment groups: external-beam radiotherapy alone (EBRT), EBRT with brachytherapy (EBRT + B), and hormone therapy either pre-EBRT or post-EBRT (EBRT + H). All patients have been followed for 1 to 17 months and a total of 521 posttreatment PSA determinations have been made. In 91 of 110 patients (83%) PSA was elevated pretreatment and correlated with clinical stage and subsequent relapse. There was no association with Gleason grade, assigned treatment group, or lymph node involvement. Acid phosphatase was elevated in only 31% of the patients initially and had no predictive value in subsequent failure. Nine patients have developed local and/or distant recurrence. None of the patients who failed had their PSA return to normal whereas 74 of 101 (73%) of the remainder have done so. Levels of PSA that do not return to normal during follow-up probably indicate active disease, often without evidence of clinical relapse. The authors conclude that PSA is a useful tumor marker for monitoring response to radiotherapy and may be a predictor of eventual failure thus identifying patients eligible for early intervention therapy as and when it becomes available.

Acid Phosphatase↗
PubMed1990

The role of radiotherapy in the treatment of muscle invasive bladder cancer.

The treatment of muscle invasive bladder cancer still remains controversial. It is becoming more clear, however, that attempts to retain the functional capacity of the urinary bladder by the use of non-surgical methods may be of benefit in the long-term. Studies using radiotherapy in combination with chemotherapeutic agents or intravesicle sensitizers, or the use of radiotherapy alone, but optimized (i.e., brachytherapy and altered fractionation) may be able to achieve improved local control whilst retaining a functional bladder. Attempts to couple this with improved survival due to the sterilization of occult metastases is still subject to much debate.

Antineoplastic Agents↗