Moderate hypofractionation: long-term toxicity results of prostate bed radiotherapy (FRAME-PROSTATE)

Moderately hypofractionated radiotherapy (m-HRT) is a standard of care in the radical treatment of localized prostate cancer (PCa). Still, its role after radical prostatectomy (RP) is yet to be defined. We present long-term outcome and toxicity results of m-HRT in the post-prostatectomy setting.

Retrospective analysis of 172 PCa patients treated with daily volumetric image-guided Tomotherapy-based m-HRT between 2013 and 2020. For outcome and toxicity endpoints, we used Kaplan-Meier survival curves and the chi-square test for univariate analysis.

The median time from RP to m-HRT was 11 months (interquartile [IQR], 8.3-31.4). The median total dose to the prostate bed was 69.75 Gy (IQR, 65.25-72 Gy) (2.25 Gy per fraction). With a median follow-up of 8.25 years (IQR 7.06-9.17 years), 10-year overall survival (OS), metastasis-free survival (MFS), and biochemical relapse-free survival (b-RFS) were 98.8% (95% CI, 95.4-99.7), 85.9% (95% CI, 79.7-90.3), and 82.4% (95% CI, 75.8-87.3), respectively. Late genitourinary (GU) toxicity of grade ≥ 2 was observed in 14 (8.1%) patients. The 10-year freedom from late grade ≥ 2 GU toxicity was 89.8% (95% CI, 83.2-93.8%). Late gastrointestinal (GI) toxicity grade ≥ 2 was reported in 2 (1.1%) patients. The 10-year freedom from late grade ≥ 2 GI toxicity was 98.8% (95% CI, 95.3-99.7%). At univariate analysis, acute GU toxicity was associated with late GU toxicity (p = 0.016).

Our long-term results confirm the critical role of modern radiotherapy in curing PCa in the post-operative setting, reducing overall treatment time and the risk of toxicity.