High-dose-rate brachytherapy boost for prostate cancer treatment: Different combinations of hypofractionated regimens and clinical outcomes

Purpose: To report the outcomes of our high-dose-rate brachytherapy (HDR-BT) boost experience in localized prostate cancer treated with different combinations of radiation doses and fractionation.

Material and methods: Between 1999 and 2011, 832 patients were treated with different regimens of external beam radiotherapy (EBRT) and HDR-BT. These regimens were converted into three biologically effective dose (BED) groups. The biochemical failure-free survival (BFFS), reported with the phoenix definition and prostate-specific antigen (PSA) >0.2ng/ml at 5-year, genitourinary (GU) and gastrointestinal (GI) toxicities were compared between the groups.

Results: The 5-, 10-year BFFS for the entire cohort were 94.6% and 92.5%, for overall survival (OS) 96.1% and 80.3% and for prostate cancer-specific survival (PCSS) 99.5% and 97.8%. The percentage of patients with a 5-year PSA level <0.2ng/ml was 68.6%, 78.7% and 86.7% in the BED group of <250, 250-260 and >260Gy (p=0.005) while the 5-year BFFS rates according to phoenix definition were 97.3%, 94.3% and 94.9% for BED group <250, 250-260 and >260Gy (p=0.453). On multivariate logistic regression, patients in the BED>260Gy group were significantly more likely to remain free from 5-year PSA values ≥0.2ng/mL compared with those in the BED<250Gy group (OR: 0.350, p=0.011). Grade≥3 acute GU toxicity was reported in 2 patients (4.7%) for BED>260Gy while grade≥3 late GU toxicity was reported in 6 (1.7%) and 9 (4.9%) patients for 250-260Gy and >260Gy BED groups.

Conclusions: The increase in BED with the hypofractionated regimens correlates with an improvement in biochemical control with of urinary toxicity. This increase in urinary toxicity is small and clinically acceptable.