Individual patient data meta-analysis of correlation of biochemical recurrence with adverse late toxic events following prostate radiotherapy

The association between late toxicity and biochemical recurrence (BCR) following prostate radiotherapy (RT) is unclear. An individual patient data (IPD) meta-analysis of randomized phase 3 trial of conventionally fractionated (CF) or moderately hypofractionated (MFH) RT evaluated the relationship of late gastrointestinal (GI) or genitourinary (GU) toxicity with BCR. Seven trials met all eligilibity criteria, with a total of 6,761 patients (CF: n=4,333; MHF: n=2,428). Median follow-up was 72 months (IQR 61-94). BCR occurred in 17.0% of patients. The rate of late grade ≥ 2 GI and GU toxicity was 14.3% and 15,5%, respectively. BCR was inversely associated with late grade ≥ 2 GI toxicity (sHR 0.64; p=0.03) but not with late grade ≥ 2 GU toxicity (sHR 1.06; p=0.78). The authors conclude that late grade ≥2 GI toxicity was significantly associated with lower rates of BCR. This may be related to the impact of prostatic motion during treatment, specifically anterosuperior motion of the prostate that would increase the dose to the rectum and to posterior dominant intraprostetic lesions.