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Introduction To identify differences in acute urinary and sexual toxicity between a 6-fraction and 2-fraction high-dose-rate brachytherapy monotherapy regimen and correlate dosimetric constraints to short-term toxicity. Methods A single institution retrospective study of 116 men with prostate cancer treated with HDR monotherapy from 2010 to 2015 was conducted. Eighty-one men had 7.25 Gy × 6-fractions and 35 men had 13.5 Gy × 2-fractions. Patients had two CT-planned implants spaced 1–2 weeks apart. Patient baseline characteristics, International Prostate Symptom Scores (IPSS) and Sexual Health Inventory for Men (SHIM) scores were collected pre-treatment and 3, 6 and 12 months post-implantation. Mixed effect modelling was undertaken to compare baseline, 1–6 month and 7–12 month scores between groups. Poisson regression analysis was performed to correlate dosimetric constraints with acute toxicity. Results There was no difference between baseline and post-implantation IPSS scores between 6-fraction and 2-fraction groups. SHIM scores for men treated with 6-fractions had a steeper decline at 1–6 months, but resolved at 7–12 months. Pre-treatment alpha-blocker use correlated with worse short-term acute urinary toxicity. Worsened SHIM score correlated with increasing age, diabetes mellitus and androgen-deprivation therapy. In a dosimetric analysis of outcomes, prostate V150 dose and bladder wall (D01.cc, D1cc, D2cc) dose correlated with increased IPSS score. Conclusion No increased acute genitourinary or sexual dysfunction has been observed in men when transitioning from 6-fraction to 2-fraction HDR monotherapy. A dosimetric correlation was found between the V150 and bladder wall doses for acute urinary toxicity. Future research should continue to standardize and validate dose constraints for prostate HDR monotherapy patients.

Purpose: To evaluate the dosimetric effect of catheter displacement on target coverage and doses to organs at risks (OARs) in high dose rate prostate brachytherapy. Methods: CT simulations from 21 prostate cancer patients treated with HDR monotherapy (7.25 Gy × 6 fractions) were used. The prostate CTV and OARs were contoured on the 3D‐CT. Treatment plans were optimized using an inverse planning simulated annealing algorithm and graphical optimization to ensure dosimetry objectives: target coverage (CTV D90=100–115%, V100 >97%, and V150

Purpose: The Strut‐Adjusted Volume Implant (SAVI) is a partial breast irradiation applicator. We developed a method to reconstruct the 3D device location using scout images to provide applicator position and proper expansion verification. We also used this technique to evaluate interfraction motion. Methods: The SAVI device was implanted in a lumpectomy cavity. The patient was aligned by CT lasers and skin tattoos to ensure reproducible setup. A post‐operative CT scan was performed for treatment planning. The patient was treated in 10 fractions over the course of 5 days. Daily CT scans and anterior and lateral scout scans were acquired prior to each fraction. Radio‐opaque markers located on three of the struts were localized using a peak detection filter. The location of each marker on the 2D scout image was backprojected towards the CT x‐ray source. Each 3D marker position was reconstructed at the backprojection intersection. The 3D marker position was compared to the location in the 3D CTimage. The interfractional displacement of the device was assessed from the reconstructed marker locations. Results: The average distance (standard deviation) between the marker positions reconstructed using the scout images and the CTimages was 0.76 (0.28) mm. Using the scout image data, the average interfractional device movement (standard deviation) in the SI, AP, and LR directions, and 3D was 0.51 (0.46) mm, 0.95 (0.81) mm, 0.73 (0.61) mm, and 1.56 (0.68) mm. Conclusion: SAVI interfraction motion can be accurately measured using scout images. The patient setup for partial breast brachytherapy can be improved by correcting the applicator displacement. This proposed technique eliminates the need for CT verifications, and therefore additional dose to the patient, while still accurately identifying applicator displacement.