High-dose-rate Brachytherapy Monotherapy in Patients With Localised Prostate Cancer: Dose Modelling and Optimisation Using Computer Algorithms.

AIMS: Interstitial high-dose-rate brachytherapy (HDR-BT) is an effective therapy modality for patients with localized prostate carcinoma. The objectives of the study were to optimise the therapy regime variables using two models: response surface methodology (RSM) and artificial neural network (ANN). MATERIALS AND METHODS: Thirty-one studies with 5651 patients were included (2078 patients presented as low-risk, 3077 patients with intermediate-risk, and 496 patients with high-risk). A comparison of these therapy schedules was carried out using an effective biologically effective dose (BEDef) that was calculated assuming the number of treatment days and dose (D) per day. The modelling and optimization of therapy parameters (BEDef and risk level) in order to obtain the maximum biochemical free survival (BFS) were carried out by the RSM and ANN models. RESULTS: An optimal treatment schedule (BFS = 97%) for patients presented with low-risk biochemical recurrence would be D = 26 Gy applied in one application, 2 fractions at least 6 h apart, within an overall treatment time of 1 day (BEDef = 251 Gy) by the RSM and ANN model. For patients presented with intermediate- or high-risk an optimal treatment regime (BFS = 94% and 90%, respectively) would be D = 38 Gy applied in one application, 4 fractions at least 6 h apart, with an overall treatment time of 2 days (BEDef = 279 Gy) by the RSM and ANN models. CONCLUSIONS: The RSM and ANN models determine almost the same optimal values for the set of predicted therapy parameters that make a feasible selection of an optimal treatment regime.

Preoperative Gleason score, percent of positive prostate biopsies and PSA in predicting biochemical recurrence after radical prostatectomy.

PURPOSE: To determine the factors that can improve the prediction of biochemical recurrence after radical prostatectomy for the patients with prostate adenocarcinoma. METHODS: Our study included 182 patients with prostate adenocarcinoma who were biopsied and underwent radical surgical treatment at the Clinic of Urology, Clinical Center of Serbia, Medical Faculty in Belgrade from 1994 to 2004. Patients were prospectively followed-up and monitored for a minimum of 8 years and data were statistically processed by multivariate regression analysis. We arranged the predictors into 3 regressive models. In the first model the predictors were clinical stage of the disease, preoperative Gleason score, F/T PSA ratio and PSA. In the second model these predictors were accompanied with the number of positive biopsies and percent of positive prostate biopsies. In the third model, patient follow-up was added to the predictors. In all 3 models biochemical recurrence was considered as a dependent variable. RESULTS: On multivariate analysis, patient follow-up (p<0.0001), percent of positive prostate biopsies (p<0.0001), bioptic Gleason score (p<0.0001) and preoperative PSA (p<0.003) were significant independent predictors of biochemical recurrence. The most successful prediction of recurrence that provided accurate prognosis for 80% of the patients was obtained by the third model using the percent of positive prostate biopsies, PSA and patient follow-up. CONCLUSION: As stated in multivariate analysis, the independent predictors according to the significance are the follows: patient follow-up, percent of positive prostate biopsies, bioptic Gleason score and preoperative PSA, whereas preoperative F/T PSA ratio is dependent predictor. The number of positive biopsies and clinical stage of the disease are of no significance.

Conventional conformal radiotherapy vs intracavitary brachytherapy for the adjuvant postoperative treatment of cervical cancer: a comparative dosimetric study.

OBJECTIVES: The aim of this pilot study is to evaluate the feasibility of 3D-conformal radiotherapy (3D-CRT) in the adjuvant postoperative radiotherapy of the vaginal cuff and upper third of present vaginal tissue. METHODS: The representative patient (FIGO IB; PH: squamous cell carcinoma) was referred for adjuvant post-hysterectomy radiotherapy. A whole pelvis irradiation with concomitant high-dose-rate intracavitary brachytherapy (HDR-ICBT) was applied. HDR-ICBT total dose of 24 Gy in four fractions/one fraction per week was delivered to the vaginal cuff using two Fletcher-Suit ovoids. The feasibility of change from HDR-ICBT to CRT was evaluated by generating of three different plans using 10 MV photon beams shaped by multileaf collimator. RESULTS AND DISCUSSION: The referent volume received HDR-ICBT prescribed dose. The maximum ICBT percentage dose to the rectum and urinary bladder was 101% and 106% respectively. In all 3D-CRT plans almost 100% of planning target volume (PTV) was covered by 95% therapy isodose surface. From 12 - 13% of the rectum and 1-3% urinary bladder volume were covered by 100% isodose surface, with the highest maximum dose of 104% and 101%, respectively. Comparison of the PTV dose coverage and the maximum dose to the rectum and urinary bladder for HDR-ICBT and 3D-CRT plans showed no major difference. CONCLUSION; 3D-CRT could be considered as adequate replacement for ICBT in the adjuvant postoperative treatment of the vaginal cuff and upper thi-rd of present vaginal tissue. Time-dose-fractionation pattern for HDR-ICBT may be safely applied for 3D-CRT.

External beam radiotherapy plus brachytherapy boost in treatment of anal canal carcinoma.

PURPOSE: Radiotherapy has been the standard treatment of anal canal carcinoma for the last three decades. However, there are still many open questions such as optimal radiation technique, adequate boost dose or best chemotherapy regimen. Beside cure and local control, other important goals are sphincter salvage and avoidance of a permanent colostomy, i.e. morbidity minimization. MATERIAL AND METHODS: At the Institute for Oncology and Radiology of Serbia, between March 1997 and May 2004, patients with anal canal carcinoma were treated with combined external beam radiotherapy and brachytherapy boost as primary treatment modality. Initially, external beam radiotherapy was applied with two opposed parallel fields and dose ranged from 40-50 Gy and after that patient continued the treatment with brachytherapy boost (intraluminal or interstitial) with doses ranged from 10-25 Gy. Total tumor dose in combined radiotherapy treatment ranged from 55-70 Gy. RESULTS: Out of 21 patients, acute complications were registered in 15 patients (71.4%) and the most frequent was dermatitis. Complete response after radiotherapy was registered in 17 patients (81%). In the median follow up time of 42 months, five-year overall survival was 71% and disease free survival was 61%. Late sequelas were registered in 14 patients (66.7%), but they were low grade. CONCLUSIONS: Our study shows results using external beam radiotherapy and brachytherapy boost as single modality treatment, but we need more randomized trial to improve better local control and minimize toxicity.