Does prostate volume has an impact on biochemical failure in patients with localized prostate cancer treated with HDR boost?

Purpose: To compare biochemical failure free survival (BFFS) of patients with small and large prostate glands treated with external beam radiation therapy (EBRT) and HDR (high dose rate) brachytherapy boost.

Materials And Methods: Between 2002 and 2012, 548 patients were treated with EBRT followed by HDR boost. The effect of covariates and prostate volume on biochemical failure was analyzed by survival analysis and Cox regression model.

Results: The median follow-up and age were not different between the two groups. The mean prostate gland volume at the time of CT planning was 48.1 and 76.0cc in small (<60cc) and large (⩾ 60cc) prostate volume, respectively (p<0.001). When PSA bounces were excluded, there was no significant difference between the two groups with a 5-years BFFS of 95.8% vs 92.3%, p=0.094. There were no significant differences between the two groups for urinary symptoms (IPSS) as well as acute and late GI toxicities.

Conclusions: This study showed that a HDR brachytherapy boost in large prostate gland cases is feasible at the price of increased PSA bounces. When the benign bounces are excluded, there is no significant difference between the two groups for tumor control and toxicity. Therefore, in our experience, there is no rational precluding the use of HDR boost in patients with a prostate size of 60 cc or more so long as an adequate dosimetry is achievable.