RADICALS-RT Final Results: No Benefit of aRT After RP

What is the ideal timing of radiotherapy (RT) after radical prostatectomy (RP) for prostate cancer? The RADICALS-RT trial, the largest study ever conducted examining the use of adjuvant RT (aRT) for prostate cancer, sought new evidence to answer this question. Professor Noel Clarke presented the results at the European Society for Medical Oncology Congress 2023.

While an early end point of biochemical progression-free survival was previously reported, new data led to this report on the primary end point, freedom from distant metastases (FFDM).

A total of 1396 patients with prostate cancer and a postoperative prostate-specific antigen (PSA) ≤0.2 ng/ml and 1 or more risk factors (pT3/4, Gleason 7-10, positive margins, or preoperative PSA ≥10 ng/ml) were included in the study. Between October 2007 and December 2016, patients were randomized ≤22 weeks after RP to receive either aRT (n=697) or observation plus salvage RT (sRT; n=699) for PSA failure, defined as PSA ≥0.1ng/ml or 3 consecutive rises.

The primary end point of FFDM needed over 1200 patients for 80% power to detect an improvement from 90% to 95% at 10 years with aRT. The secondary end points included overall survival (OS), safety, and patient-reported end points (1, 5, and 10 years). Standard survival analysis methods were used.

Median patient age was 65 years, and median follow-up was 8 years. A total of 93% of patients in the aRT arm (650/697) began RT within 5 months, while 39% of patients in the observation-plus-sRT arm (270/699) started with RT.

The median PSA at time of sRT was 0.2 ng/ml. Twenty-four percent of patients receiving aRT and 27% of patients receiving observation plus sRT reported receiving hormone therapy along with RT.

With 80 events, FFDM at 10 years was 93% in the aRT arm versus 90% in the observation-plus-sRT arm (hazard ratio [HR], 0.68; 95% CI, 0.43-1.07; P=.095). The OS at 10 years was 88% in the aRT arm versus 87% in the observation-plus-sRT arm (HR, 0.98; 95% CI, 0.67-1.44; P=.92). Self-reported urinary incontinence and fecal incontinence were worse at 1-year follow-up for patients who received aRT (P<.001).

The final results from the RADICALS-RT trial did not demonstrate a meaningful benefit of aRT after RP in this patient group, and aRT was found to increase the risk of urinary and bowel morbidity. The current standard treatment administered after RP should consist of an observation policy with sRT for PSA failure.