Second-Line Radiation Therapy for Locally Recurrent Prostate Cancer After Focal Therapy: A Single Institution Matched-Pair Analysis.

BACKGROUND

Focal therapy (FT) is an alternative to prostate radiation therapy (RT) that targets a single intraprostatic tumor. When FT fails, second-line, whole-prostate radiation therapy (SRT) is considered; however, limited safety data is available. We report toxicity outcomes in patients undergoing SRT after FT.

METHODS

Retrospective analysis of 5606 prostate cancer patients evaluated from 2000 to 2024. Toxicities of patients who underwent SRT after FT were compared to patients treated with RT-alone. Propensity score matching balanced baseline patient and tumor characteristics. Differences in acute and late toxicities between cohorts were compared.

RESULTS

A total of 114 matched patients were analyzed (38 SRT, 76 RT-alone). Among SRT patients, 71% received high-intensity focused ultrasound, 18% cryoablation, 10.5% TULSA, and 3% focal laser ablation. Median time from FT to SRT was 3.3 years (IQR 2.0-5.1). RT modality differed significantly (P < .001), with higher use of EBRT-alone (82% vs. 62%)in the SRT group. Acute grade ≥ 2 GU toxicity occurred in 47% of SRT patients versus 32% in RT-alone (P = .11); no grade ≥ 3 GU events occurred. Acute GI toxicity rates were also similar: 10.5% (SRT) versus 8% (RT-alone; P = .7), with no grade ≥ 3 events. Late grade ≥ 2 GU (42% vs. 33%; P = .4) and GI (8% vs. 6.6%; P = .9) toxicities were not significantly different between groups. Progression free survival, prostate cancer specific survival, and local recurrence was not significantly different between cohorts.

CONCLUSIONS

Acute and late GI and GU toxicities were comparable between the SRT and RT-alone cohorts. These findings support SRT as a safe and acceptable treatment option.