http://repub.eur.nl/res/aut/28920/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/34938/ 2012-01-01T00:00:00Z Organ preservation protocols that incorporate chemoradiotherapy have shown good efficacy in bladder cancer. Owing to changes in rectal filling, urinary inflow and subsequent bladder volume with bladder wall deformations, irradiation must take into account interfractional and intrafractional internal target motion. Growing evidence suggests that image guidance during irradiation is essential in order to appropriately treat bladder cancer in this way. We performed a literature search on the imaging techniques and margins used for radiation therapy planning in the context of whole-bladder and partial-bladder irradiation. The most common image-guided radiation therapy (IGRT) method was based on cone-beam CT using anisotropic margins. The role of cine-MRI for the prediction of intraindividual bladder changes, in association with cone-beam CT or ultrasonography, is promising. Drinking protocols, diet and laxatives were used in most cases to minimize large variations in bladder size and shape. IGRT is crucial for avoiding tumor undercoverage and undue toxicity during radiation therapy for bladder cancer. IGRT-based adaptive radiation therapy can be performed using cone-beam CT or ultrasonography: modeling of bladder changes with cine-MRI or other imaging techniques might also be useful for facilitating adaptive radiation therapy with personalized margins. http://repub.eur.nl/res/pub/23576/ 2011-02-01T00:00:00Z Purpose: The aim of this study was to systematically analyse the effect of catheter displacements both on target coverage and normal tissue irradiation in fractionated high dose rate (HDR) prostate brachytherapy, using a simulation study, and to define tolerances for catheter displacement ensuring that both target coverage and normal tissue doses remain clinically acceptable. Besides the effect of total implant displacement, also displacements of catheters belonging to selected template rows only were evaluated in terms of target coverage and normal tissue dose, in order to analyse the change in dose distribution as a function of catheter dwell weight and catheter location. Material and methods: Five representative implant geometries, with 17 catheters each, were selected. The clinical treatment plan was compared to treatment plans in which an entire implant displacement in caudal direction over 3, 5, 7 and 10 mm was simulated. Besides, treatment plans were simulated considering a displacement of either the central, most ventral or most dorsal catheter rows only, over 5 mm caudally. Results: Due to displacement of the entire implant the target coverage drops below the tolerance of 93% for all displacements studied. The effect of displacement of the entire implant on organs at risk strongly depended on the patient anatomy; e.g., for 80% of the implant geometries the V80 of the rectum exceeded its tolerance for all displacements. The effect of displacement of catheters belonging to selected template rows depended strongly on the relative weight of each catheter row when considering the target coverage and on its location when considering the dose in the organs at risk. Conclusion: This study supports the need for a check of the catheter locations before each fraction and correction of deviations of the catheter position exceeding 3 mm. http://repub.eur.nl/res/pub/33050/ 2010-05-01T00:00:00Z Purpose: The CyberKnife (CK), a linear accelerator mounted on a robotic device, enables excellent dose conformation to the target and minimizes dose to surrounding normal tissue. It is a very suitable device for performing hypofractionated stereotactic body radiotherapy as monotherapy for low- to intermediate-risk prostate cancer patients. We report our early experience using this technique. Materials and Methods: Between June 2008 and June 2009, 10 patients underwent CK monotherapy as treatment for their prostate cancer (stage ≤T2b, Gleason score (GS) ≤7, initial PSA ≤15μg/L). The prescribed dose was 38 Gy in four daily fractions of 9.5 Gy. The International Prostate Symptom Score and Radiation Therapy Oncology Group symptom scale were prospectively administered before and at 0.5, 1, 2, 3, 6, and 12 months. Results: Median age of the patients was 71 years (range, 66-76). Three patients had stage T2a and 7a T1c disease, one patient had GS of 7, and all others had GS of 6. Median follow-up was 5.1 months. Median initial PSA was 8.3 ng/mL (range, 1.3-13.6 ng/mL). Median planning target volume delineated on computed tomography after matching with the magnetic resonance imaging scan was 107 cc (range, 42-158 cc). The median V100 of the prostate was 95.8% (range, 94.8-97.2). The D95 of the prostate was 38.3 Gy (range, 38.1-38.8 Gy). The constraints for the bladder, rectum, and urethra were well met. The International Prostate Symptom Scores after 3 months were stable compared with the pretreatment scores. Urinary and bowel Radiation Therapy Oncology Group symptoms were mild and within the expected levels. Conclusions: This regimen of stereotactic CK monotherapy for low- to intermediate-risk prostate cancer with excellent dose coverage of the prostate was well tolerated. Data collection is ongoing for further assessment of toxicity and PSA response.