Local Radiotherapy Improves Survival in Patients With Oligometastatic Prostate Cancer

Radiotherapy to the prostate can improve survival in patients with newly-diagnosed metastatic prostate cancer who have a low metastatic disease burden, though not in those with a higher burden of disease, according to results reported at ESMO 2018 Congress in Munich.

Patients with metastatic prostate cancer typically die within around five years, so there is a need for more effective treatment. We wanted to know if radiotherapy to the prostate might not only improve local control but also slow progression of metastatic disease.” “Standard treatment for men newly diagnosed with metastatic prostate cancer is currently drug treatment alone,” said the lead author Chris Parker, clinical oncologist, The Royal Marsden NHS Foundation Trust, Sutton, UK. The researchers hypothesized that local radiotherapy might not improve local control of primary tumors and thereby slow overall progression of metastatic disease and improve survival.

The STAMPEDE study was a multi-arm, multi-stage platform protocol that included a randomised phase III comparison to test whether radiotherapy to the prostate improves overall survival in men with newly diagnosed metastatic prostate cancer. A total of 2061 patients were randomly allocated to standard of care (SOC) or to SOC plus radiotherapy to the prostate. Standard-of-care (SOC) was lifelong androgen deprivation therapy (ADT), with early docetaxel permitted from 2016. The primary outcome measure was death from any cause; secondary measures included failure-free survival (FFS).

Overall results showed that prostate radiotherapy improved failure-free survival (HR = 0.68, 95% CI: 0.68-0.84) but not OS (HR = 0.92, 95% CI: 0.80-1.06). However, a prespecified subgroup analysis showed OS was improved in patients with lower metastatic burden who received prostate radiotherapy (n = 819, HR = 0.68, 95% CI: 0.52-0.90) but not in those with higher metastatic burden (n = 1120, HR=1.07, 95%CI 0.90, 1.28). Higher burden of disease was defined as four or more bone metastases with at least one outside the axial skeleton and/or visceral metastases.

Dr Parker reported that radiotherapy to the prostate was well tolerated, with 5% of patients having grade 3-4 adverse events during treatment and 4% following treatment.

“Prostate radiotherapy improves the survival of men with metastatic prostate cancer who have a low disease burden,” Dr Parker concluded. He recommended that, in addition to drug treatment, prostate radiotherapy should be a standard treatment option for men with oligometastatic disease.—Kara Rosania