[en] Purpose: A disadvantage of ovoid shields in a Fletcher-type applicator is that these shields cause artifacts on post implant CT images. CT images, however, make it possible to calculate the dose distribution in the rectum and the bladder. To be able to estimate the possible advantage of having CT information over the use of ovoid shields without having CT information, we investigated the influence of shielding segments in a Fletcher-type Selectron-LDR applicator on the dose distribution in rectum and bladder. Methods and Materials: Contours of rectum and bladder were delineated on transaxial CT slices of 15 unshielded applications. Of the volumes contained within these structures dose-volume histograms (DVHs) were calculated. In a similar way, DVHs of simulated shielded applications were calculated. The reduction, due to shielding, of the dose to the 2 cm³ (D₂) and 5 cm³ (D₅) volume of the cumulative DVHs of rectum and bladder, were determined. An isodose pattern in the sagittal plane through the center of each applicator was plotted to compare the location of the shielded area with the location of maximum dose in rectum and bladder in the unshielded situation. In two cases local dose reductions to the rectal wall were determined by calculating the dose in points at 10-mm intervals on the rectal contours. Results: For the rectum, the reduction of D₂ ranged from 0 to 11.1%, with an average of 5.0%; the reduction of D₅ ranged from 2.3 to 12.1%, with an average of 6.4%. The reduction of D₂ and D₅ for the bladder ranged from 0 to 11.9% and from 0 to 11.6%, with average values of 2.2 and 2.6%, respectively. In 8 out of 15 cases the rectal maximum dose was located inferior to the shielded area. In all cases except one the bladder maximum dose was located superior to the shielded area. Local dose reductions on the rectal wall can be as high as 30% or more in an optimally shielded area. Conclusions: Reductions of D₂ and D₅ to rectum and bladder due to shielding are rather small, because the shielded area does usually not coincide with the high dose region and even if it does, the shielded area is too small to result in large reductions of these values. Because local dose reductions vary largely, one should proceed with caution when calculating the dose in just one rectal or bladder reference point. Because large overall dose reductions cannot be achieved with shielding, it is safe to use an unshielded applicator when post implant CT images are used to realize optimized dose distributions

[en] Background and Purpose: To investigate possible relationships between the dose to the sub-segments of the lower urinary tract and lower urinary tract symptoms (LUTS) after brachytherapy of the prostate. Materials and Methods: This study involved 225 patients treated for prostate cancer with I-125 seeds. Post-implant dose-volume histograms of the prostate, urethra, bladder wall, bladder neck and external sphincter were determined. Endpoints were the mean and the maximum International Prostate Symptom Score (IPSS) during the first 3 months after the treatment. For binary analysis the patients were stratified in a group with enhanced LUTS and a group with non-enhanced LUTS. Results: The dose to 0.5 cm³ of the bladder neck ‘D_0.5cc-blne’ (p = 0.002 and p = 0.005), the prostate volume prior to treatment ‘V_pr-0’ (p = 0.005 and p = 0.024) and the pre-treatment IPSS (both p < 0.001) were independently correlated with mean and maximum IPSS, respectively. Of the patients with a D_0.5cc-blne ⩾ 175 Gy and a V_pr-0 ⩾ 42 cm³, 68% suffered from enhanced LUTS, against just 30% of the other patients (p < 0.0001). Conclusions: Pre-treatment IPSS, prostate volume and dose to the bladder neck are correlated with post-implant IPSS. A combination of a large prostate and a high dose to the bladder neck is highly predictive for enhanced early LUTS

[en] Background and purpose: In a recent study on patients with transitional cell cancer of the bladder treated with curative radiotherapy following TUR-T, we demonstrated that a low apoptotic index and p53 positivity were associated with poor local control. The purpose of this study was to assess the prognostic significance of additional markers implicated in regulation of cell cycle and apoptosis. Patients and methods: Bcl-2, Bax and p21 positivity were detected immunohistochemically on paraffin-embedded pre-treatment biopsies from 83 patients with invasive transitional cell cancer (TCC) of the bladder, treated with radiotherapy. In addition, markers determined in an earlier analysis, i.e.: p53, apoptotic index, cyclin D1, retinoblastoma protein and Ki-67 were included in the multivariate analysis. A stepwise proportional hazard analysis was performed, adjusting for classic prognostic factors (T-stage, grade, multifocality and macroscopic completeness of the TUR). Positivity was defined as >10% of tumor cells staining positive for Bcl-2, Bax and p21, and >20% for p53. Results: Bcl-2 positivity was found in 63%, Bax was positive in 52% and p21 in 55% of cases. In the PH analysis Bcl-2 positivity was found to be related to poor local control (36 vs. 72% at 3 years; P=0.003), as well as to shorter disease-specific survival (74 vs. 94% at 3 years; P=0.017). Evidence for an adverse effect of p53 positivity was also found (local control: 32 vs. 69% at 3 years;P=0.037, disease-specific survival: 76 vs. 92% at 3 years; P=0.043). In an additional PH analysis, we found poor local control rates for bladder cancers with combined Bcl-2 and p53 positivity (17 vs. 65% at 3 years; P=0.0017), and lower disease specific survival (60 vs. 92%; P=0.0024), disease-free survival (7 vs.35%, P=0.0023) and overall survival (39 vs. 80%; P=0.0018). Conclusion: This study provides evidence for a poor outcome in patients treated with radiotherapy for TCC of the bladder expressing both Bcl-2 and p53. This relationship was found for local control and disease-free, disease-specific and overall survival

[en] Purpose: Lower urinary tract symptoms are frequently observed after I-125 seed implantation of the prostate. More knowledge about causes and predictors is necessary to be able to develop less toxic implantation techniques. The aim of this study was to identify implantation related factors that contribute to post-implant urinary morbidity. Materials and methods: Analysed was a group of 72 patients that filled in a symptom score questionnaire before, 3 months and 6 months after implantation as well as a group of 15 patients that suffered from acute urinary retention. Several dose-volume parameters of prostate, urethra and bladder wall were determined based on a post-implant TRUS-CT scan. Results: The dose to a 1 cm³ hotspot in the bladder wall (D1cc-bl) as well as the prostate volume were independently correlated with urinary morbidity symptom scores at 3 months (p = 0.006 and p = 0.005, respectively) and at 6 months (p = 0.001 and p = 0.015, respectively) after implantation. The number of implanted seeds and the D1cc-bl were significant discriminators (p < 0.001 and p = 0.015, respectively) for either mild or severe early urinary morbidity. Conclusion: Bladder hotspot dose appears to be an important dosimetric predictor for urinary morbidity both at 3 months and at 6 months after implantation. Other predictors are prostate volume, or equivalently, the number of implanted seeds

[en] Purpose: After prostate implantation, dose calculation is usually based on a single imaging session, assuming no geometrical changes occur during the months of dose accumulation. In this study, the effect of changes in anatomy and implant geometry on the dose distribution was investigated. Materials and methods: One day, 1 month and 312 months after seed implantation, a combined TRUS-CT scan was made of 13 patients. Based on these scans changes in dose rate distribution were determined in prostate, urethra and bladder and a 'geometry corrected' dose distribution was estimated. Results: When based on the day-1 scan, parameters representing high dose volumes in prostate and urethra were largely underestimated: V150 of the prostate 18+/-10% and V120 of the urethra 47+/-32%. The dose to a 2cm³ hotspot in the bladder wall (D2cc), however, was overestimated by 31+/-35%. Parameters based on scans 1 month post-implant or later were all within +/-5% of geometry corrected values. Conclusion: Values meant to indicate the adequacy of dose coverage of the prostate, V100 and D90, were not influenced by geometrical changes and were independent of the post-implant scan date. Other parameters representing high dose volumes changed strongly within the first month after implantation