Observation, Not Radiotherapy, After Radical Prostatectomy

Adjuvant radiotherapy after radical prostatectomy provided no meaningful benefit in patients with prostate cancer but increased the risk for urinary and bowel morbidity compared with men followed with observation alone, according to the latest results from the phase 3 RADICALS-RT trial.

The new findings showed no difference in the rate of 10-year freedom from distant metastases or overall survival in patients who received adjuvant radiotherapy vs those who underwent observation with salvage radiotherapy if their disease progressed and provided further confirmation of earlier results reported in The Lancet in 2020.

Observation with early salvage radiotherapy in cases of biochemical failure should be the standard of care, concluded study co-author Noel Clarke, MBBS, who presented the results at the European Society for Medical Oncology (ESMO) Congress 2023 in Madrid on October 20.

Invited discussant and session co-chair Shahneed Sandhu, MBBS, said that the findings definitively confirm the value of observation with salvage radiotherapy over adjuvant radiotherapy in this patient population.

“The approach of early salvage radiotherapy spared morbidity [from] radiation in the vast majority of patients, and further bowel and bladder toxicity is reduced in the setting of salvage radiotherapy,” said Sandhu, an associate professor and consultant medical oncologist at Peter MacCallum Cancer Centre, Victoria, Australia.

The aim of the RADICALS-RT study was to clarify the optimal timing for radiotherapy after radical prostatectomy in men with prostate cancer, which previously had been uncertain.

In the study, 697 patients were randomly assigned to adjuvant radiotherapy and 699 to observation with salvage radiotherapy. Participants had undergone radical prostatectomy; had a postoperative prostate-specific antigen (PSA) level ≤ 0.2 ng/mL; and at least one risk factor for cancer relapse, including pathologic T-stage III or IV, Gleason score of 7-10, positive margins, or preoperative PSA ≥ 10 ng/mL.

Patients in the observation arm received salvage radiotherapy if they experienced two consecutive PSA increases ≥ 0.1 ng/mL or three consecutive rises.

Overall, the investigators found similar rates of 10-year freedom from distant metastases in both arms: 93% in the adjuvant radiotherapy group vs 90% in the observation group (hazard ratio [HR], 0.68; P = .095). The 10-year overall survival rates were similar as well: 88% in the adjuvant radiotherapy group and 87% in the observation group (HR, 0.98; = .92).

However, self-reported urinary and fecal incontinence rates at 1 year were significantly higher in the adjuvant radiotherapy group vs the observation group, 60% of whom had not received salvage radiotherapy at that time.

Secondary outcome measures, including biochemical progression-free survival and time to further hormone therapy, were also similar in the treatment and observation arms.

Overall, the trial results “support the use of early salvage radiotherapy for PSA failure after radical prostatectomy rather than early adjuvant intervention, ” concluded Clarke, a professor and consultant urologist at The Christie Hospital and Salford Royal Hospital, Manchester, United Kingdom.

And when biochemical recurrence does occur, Sandhu noted that prostate-specific membrane antigen PET is increasingly used in practice to help “define the extent of disease” and “tailor radiation fields.”

Clarke reported serving on advisory boards for Janssen, Astellas, and Bayer. Sandhu reported receiving research grant support and/or serving as a consultant or advisor for Advanced Accelerator Application (a Novartis company), AstraZeneca, Merck Sharp and Dohme, Roche/Genentech, Amgen, Pfizer, Merck Serono, Bristol-Myers Squibb, Novartis, Janssen, and Sehnwa.

ESMO Congress 2023: Abstract #1764O. Presented October 20, 2023.

Sharon Worcester, MA, is an award-winning medical journalist based in Birmingham, Alabama, writing for Medscape, MDedge and other affiliate sites. She currently covers oncology, but she has also written on a variety of other medical specialties and healthcare topics. She can be reached at [email protected] or on Twitter: @SW_MedReporter.

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