Intra-operative pubic arch interference during prostate seed brachytherapy in patients with CT-based pubic arch interference of ≤1 cm

Purpose: There are only a few reports on the frequency of intra-operative pubic arch interference (I-PAI) during prostate seed brachytherapy (PB). Materials and methods: Two hundred and forty-three patients with a CT-based pubic arch interference (PAI) of ≤1 cm and a prostate volume of ≤50-60 cc underwent PB. Those patients requiring needle repositioning by ≥0.5 cm on the template were scored as having I-PAI. The incidence of I-PAI and its impact on biochemical control were analyzed. Results: Intra-operative PAI was encountered in 47 (19.3%) patients. Forty two patients (17.3%) had I-PAI in 1-2 needles, two (0.8%) had I-PAI in four needles and three patients (1.2%) had I-PAI in six needles. Overall, 1.4% of needles required repositioning due to I-PAI. BMI > 27 kg/m² and wider (>75 mm) pubic bone separation at mid ramus (PS-ML) were associated with a lower incidence of I-PAI. At a median follow-up of 50.1 months, the 3- and 5-year bPFS was 97.3% and 95.2%, respectively. The 5-year bPFS rates for patients with and without I-PAI were 95.6% and 95%, respectively (p = 0.28). Conclusions: The use of CT-based PAI of ≤1 cm as a selection criterion for PB is a simple and reliable method for minimizing the incidence of I-PAI and maintaining excellent biochemical control rates.