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BACKGROUND AND PURPOSE: Radiation damage to neural and vascular tissue, such as the neurovascular bundles (NVBs) and internal pudendal arteries (IPAs), during radiotherapy for prostate cancer (PCa) may cause erectile dysfunction. Neurovascular-sparing magnetic resonance-guided adaptive radiotherapy (MRgRT) aims to preserve erectile function after treatment. However, the NVBs and IPAs are not routinely contoured in current radiotherapy practice. Before neurovascular-sparing MRgRT for PCa can be implemented, the interrater agreement of the contouring of the NVBs and IPAs on pre-treatment MRI needs to be assessed. MATERIALS AND METHODS: Four radiation oncologists independently contoured the prostate, NVB, and IPA in an unselected consecutive series of 15 PCa patients, on pre-treatment MRI. Dice similarity coefficients (DSCs) for pairwise interrater agreement of contours were calculated. Additionally, the DCS of a subset of the inferior half of the NVB contours (i.e. approximately prostate midgland to apex level) was calculated. RESULTS: Median overall interrater DSC for the left and right NVB was 0.60 (IQR: 0.54 - 0.68) and 0.61 (IQR: 0.53 - 0.69) respectively and for the left and right IPA 0.59 (IQR: 0.53 - 0.64) and 0.59 (IQR: 0.52 - 0.64) respectively. Median overall interrater DSC for the inferior half of the left NVB was 0.67 (IQR: 0.58 - 0.74) and 0.67 (IQR: 0.61 - 0.71) for the right NVB. CONCLUSION: We found that the interrater agreement for the contouring of the NVB and IPA improved with enhancement of the MRI sequence as well as further training of the raters. The agreement was best in the subset of the inferior half of the NVB, where a good agreement is clinically most relevant for neurovascular-sparing MRgRT for PCa.
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PURPOSE: Determining the independent effect of additional intraoperative adaptive C-arm cone-beam CT (CBCT) planning vs. transrectal ultrasound (TRUS)-guided interactive planning alone in 125I brachytherapy for prostate cancer (PCa) on biochemical disease-free survival (BDFS). METHODS AND MATERIALS: T1/T2-stage PCa patients receiving TRUS-guided brachytherapy from 2000 to 2014 were analyzed. From October 2006, patients received additional intraoperative adaptive CBCT planning for dosimetric evaluation and subsequent remedial seed placement in underdosed areas. Patients were stratified according to the National Comprehensive Cancer Network (NCCN) risk classification. Kaplan-Meier analysis was used to estimate BDFS (primary outcome), overall survival, and PCa-specific survival (secondary outcomes). Cox regression was used to assess the relation between CBCT use and biochemical failure (BF) and overall mortality. RESULTS: In all, 1623 patients were included. Median followup was 99 months (interquartile range 70-115) for TRUS patients (n = 613) and 51 months (interquartile range 29-70) for CBCT patients (n = 1010). BF occurred 203 times and 206 patients died, 26 from PCa. For TRUS and CBCT patients, 7-year BDFS was 87.2% vs. 93.5% (log rank: p = 0.04) for low, 75.9% vs. 88.5% (p < 0.001) for intermediate, and 57.1% vs. 85.0% for high-risk patients (p < 0.001). For TRUS and CBCT patients, 7-year PCa-specific survival was 96.0% vs. 100% (p < 0.0001). After Cox regression, CBCT patients had lower hazard of BF: hazard ratio (HR) 0.25 (95% confidence interval [CI]: 0.18-0.33; p < 0.0001). Corrected for confounders, CBCT remained a predictor of BF: HR 0.51 (95% CI: 0.31-0.86; p = 0.01) but not for overall mortality: HR 0.66 (95% CI: 0.40-1.07; p = 0.09). CONCLUSIONS: Additional intraoperative adaptive CBCT planning in 125I prostate brachytherapy leads to a significant increase in BDFS in all NCCN risk groups.