Chicago, Illinois—Salvage radiotherapy combined with short-term hormone therapy led to significant improvement in metastatic-free survival (MFS) compared with salvage radiotherapy alone in patients who have undergone radical prostatectomies, according to data presented at the 2019 ASCO annual meeting.

“[Radiotherapy] is the standard salvage treatment after radical prostatectomy,” said Christian Carrie, MD, Centre Léon Bérard, and colleagues. “The role of HT [hormonotherapy] is not formally demonstrated.”

For the trial, Dr Carrie et al assessed the efficacy of radiotherapy alone versus that of radiotherapy plus hormone therapy. Specifically, they focused on progression-free survival (PFS), MFS, and overall survival (OS) in patients with biologic relapses after radical prostatectomy.

In a previous study with a median duration of 5.3 years’ follow-up, the investigators reported a PFS benefit in patients receiving radiotherapy plus hormone therapy, regardless of subgroup risks.

In the current study, Dr Carrie and colleagues randomized patients in a 1:1 ratio to undergo radiotherapy or radiotherapy plus hormonotherapy (goserelin, for 6 months); patients were stratified based on radiotherapy modality and risk group.

Assuming a 5-year PFS of 45% in the radiotherapy arm, 369 patients were needed in each arm to detect an improvement of 12% in PFS in the radiotherapy plus hormone therapy arm (90% power and 5% bilateral alpha risk), which the investigators said would possibly translate to a 10% gain in OS (75%-85% with 80% power).

Follow-up lasted for a median of 112 months as of the point of data cutoff (March 2019). Dr Carrie and his co-investigators ultimately confirmed the benefit of radiotherapy plus hormone therapy on PFS (hazard ratio [HR], 0.54; 95% CI, 0.43-0.68; P <.0001), regardless of the risk subgroup (low-risk: HR, 0.47; 95% CI, 0.28-0.80 and high-risk: HR, 0.56; 95% CI, 0.44-0.73).

Additional findings demonstrated a significant MFS improvement in the combination therapy cohort (HR, 0.73; 95% CI, 0.54-0.98; P = .034), and that the 10-year MFS was 69% with radiotherapy (95% CI, 63-74) versus 75% with radiotherapy plus hormone therapy (95% CI, 70-80).

“Salvage radiotherapy combined with short term HT [hormone therapy] significantly improved 10-years metastatic free survival compared with salvage radiotherapy alone,” Dr Carrie and his colleagues said.

“…[T]his strategy can be considered as the new standard for salvage treatment after radical prostatectomy,” they concluded.—Julie Gould

Carrie C, Magne N, Burban-Provost P, et al. Interest of short hormonotherapy (HT) associated with radiotherapy (RT) as salvage treatment for metastatic free survival (MFS) after radical prostatectomy (RP): Update at 9 years of the GETUG-AFU 16 phase III randomized trial (NCT00423475). Presented at: the 2019 ASCO Annual Meeting. Abstract: 5001.