Quality of Life, Treatment Toxicity, and Biochemical Control in Patients Treated with Dose-Escalation Brachytherapy and EBRT for Intermediate- and High-Risk Prostate Cancer

Abstract

The use of prostate brachytherapy (BT) as a dose-escalation technique in conjunction with external beam radiation therapy (EBRT) is associated with improved biochemical progression-free survival (b-PFS). This technique is also associated with increased genitourinary (GU) and gastrointestinal (GI) toxicity. This study compared b-PFS and post-treatment toxicity in patients receiving either EBRT-BT or EBRT alone. We hypothesized that patients in the EBRT-BT cohort would demonstrate improved b-PFS and an increased incidence of GU and GI toxicity. The start date of radiation was taken as t-0 to determine acute (<6 months) and late (>6 months) events. Incidence of acute and late GU and GI toxicity was obtained along with the prevalence of late toxicity 12-23 months after treatment and ≥ 24 months after treatment. Mann-Whitney U tests were used to compare cohort differences. 96 patients met inclusion criteria for the EBRT-BT cohort with median follow-up of 26.0 months. 27 patients met inclusion for the EBRT cohort with median follow-up of 11.6 months. Log-rank comparison of the b-PFS rates between the EBRT cohort (n=21, 95.2%) and the EBRT-BT cohort (n=71, 95.8%) was not significant (p = .484). Patients in the EBRT-BT cohort demonstrated a higher incidence of moderate (CTCAE v4 grade 2 or higher) GU toxicity at follow-up ≥ 6 months after treatment compared to the EBRT group (37.1% vs 9.1%, p = .091). In contrast, acute moderate GU toxicity was similar in both EBRT-BT and EBRT cohorts (48.9% vs 57.7%, p = .647). Comparison of toxicity incidence in our study approached significance in patients seen for follow-up ≥ 6 months post-treatment. In contrast, the ASCENDE-RT trial reported significantly higher acute moderate GU toxicity in the EBRT-BT treatment group (Rodda Int J Radiation Oncol Biol Phys 2017). Furthermore, our study reports no significant difference in b-PFS between the two treatment cohorts. While other studies have shown improved b-PFS in patients receiving EBRT-BT, these distinctions were noted more than 4 years (Morris Int J Radiation Oncol Biol Phys 2017) and 5 years (Sathya J Clin Oncol 2005) after the end of treatment. Thus, longer follow-up is warranted for more reliable comparison.