Prostatic Neoplasms: Wiltshire KL

Sidhom MA, Kneebone AB, Lehman M, Wiltshire KL, Millar JL, Mukherjee RK, Shakespeare TP, Tai KH. · Cancer Therapy Centre, Liverpool Hospital, NSW, Australia. · Radiother Oncol. · Pubmed #18514340 No free full text.

Abstract: BACKGROUND AND PURPOSE: Three randomised trials have demonstrated the benefit of adjuvant post-prostatectomy radiotherapy (PPRT) for high risk patients. Data also documents the effectiveness of salvage radiotherapy following a biochemical relapse post-prostatectomy. The Radiation Oncology Genito-Urinary Group recognised the need to develop consensus guidelines on to whom, when and how to deliver PPRT. MATERIALS AND METHODS: Draft guidelines were developed and refined at a consensus conference in June 2006 attended by 63 delegates where urological, radiotherapy and diagnostic imaging experts spoke on aspects of PPRT. Unresolved issues were further developed by working parties and redistributed until consensus was reached. RESULTS: Central to the recommendations is that patients with positive surgical margins, seminal vesicle invasion and/or extracapsular extension have a high risk of residual local disease and should be informed of the options of either immediate adjuvant radiotherapy or active surveillance with early salvage in the event of biochemical recurrence. Salvage radiotherapy should be instituted at the earliest confirmation of biochemical recurrence. Detailed contouring guidelines have been developed, defining the regions at risk of residual microscopic disease which should be included in the clinical target volume. The recommended doses are 60-64Gy for adjuvant, and 60-66Gy for salvage radiotherapy. The role of hormone therapy in conjunction with PPRT is yet to be defined. CONCLUSIONS: These consensus guidelines have been developed to give clinical and technical guidance to radiation oncologists and urologists in the management of high risk post-prostatectomy patients.

Wiltshire KL, Brock KK, Haider MA, Zwahlen D, Kong V, Chan E, Moseley J, Bayley A, Catton C, Chung PW, Gospodarowicz M, Milosevic M, Kneebone A, Warde P, Ménard C. · Radiation Medicine Program, Princess Margaret Hospital, University of Toronto, Toronto, Ontario, Canada. · Int J Radiat Oncol Biol Phys. · Pubmed #17967303 No free full text.

Abstract: PURPOSE: We sought to derive and validate an interdisciplinary consensus definition for the anatomic boundaries of the postoperative clinical target volume (CTV, prostate bed). METHODS AND MATERIALS: Thirty one patients who had planned for radiotherapy after radical prostatectomy were enrolled and underwent computed tomography and magnetic resonance imaging (MRI) simulation prior to radiotherapy. Through an iterative process of consultation and discussion, an interdisciplinary consensus definition was derived based on a review of published data, patterns of local failure, surgical practice, and radiologic anatomy. In validation, we analyzed the distribution of surgical clips in reference to the consensus CTV and measured spatial uncertainties in delineating the CTV and vesicourethral anastomosis. Clinical radiotherapy plans were retrospectively evaluated against the consensus CTV (prostate bed). RESULTS: Anatomic boundaries of the consensus CTV (prostate bed) are described. Surgical clips (n = 339) were well distributed throughout the CTV. The vesicourethral anastomosis was accurately localized using central sagittal computed tomography reconstruction, with a mean +/- standard deviation uncertainty of 1.8 +/- 2.5 mm. Delineation uncertainties were small for both MRI and computed tomography (mean reproducibility, 0-3.8 mm; standard deviation, 1.0-2.3); they were most pronounced in the anteroposterior and superoinferior dimensions and at the superior/posterior-most aspect of the CTV. Retrospectively, the mean +/- standard deviation CTV (prostate bed) percentage of volume receiving 100% of prescribed dose was only 77% +/- 26%. CONCLUSIONS: We propose anatomic boundaries for the CTV (prostate bed) and present evidence supporting its validity. In the absence of gross recurrence, the role of MRI in delineating the CTV remains to be confirmed. The CTV is larger than historically practiced at our institution and should be encompassed by a microscopic tumoricidal dose.

Moseley DJ, White EA, Wiltshire KL, Rosewall T, Sharpe MB, Siewerdsen JH, Bissonnette JP, Gospodarowicz M, Warde P, Catton CN, Jaffray DA. · Radiation Medicine Program, Princess Margaret Hospital, Toronto, ON, Canada. · Int J Radiat Oncol Biol Phys. · Pubmed #17293243 links to  free full text

Abstract: PURPOSE: The aim of this work was to assess the accuracy of kilovoltage (kV) cone-beam computed tomography (CBCT)-based setup corrections as compared with orthogonal megavoltage (MV) portal image-based corrections for patients undergoing external-beam radiotherapy of the prostate. METHODS AND MATERIALS: Daily cone-beam CT volumetric images were acquired after setup for patients with three intraprostatic fiducial markers. The estimated couch shifts were compared retrospectively to patient adjustments based on two orthogonal MV portal images (the current clinical standard of care in our institution). The CBCT soft-tissue based shifts were also estimated by digitally removing the gold markers in each projection to suppress the artifacts in the reconstructed volumes. A total of 256 volumetric images for 15 patients were analyzed. RESULTS: The Pearson coefficient of correlation for the patient position shifts using fiducial markers in MV vs. kV was (R2 = 0.95, 0.84, 0.81) in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions, respectively. The correlation using soft-tissue matching was as follows: R2 = 0.90, 0.49, 0.51 in the LR, AP and SI directions. A Bland-Altman analysis showed no significant trends in the data. The percentage of shifts within a +/-3-mm tolerance (the clinical action level) was 99.7%, 95.5%, 91.3% for fiducial marker matching and 99.5%, 70.3%, 78.4% for soft-tissue matching. CONCLUSIONS: Cone-beam CT is an accurate and precise tool for image guidance. It provides an equivalent means of patient setup correction for prostate patients with implanted gold fiducial markers. Use of the additional information provided by the visualization of soft-tissue structures is an active area of research.