Long-Term Findings Confirm Addition of Radiotherapy to Standard of Care in Metastatic Prostate Cancer Improves Survival

Men with low-burden, newly diagnosed metastatic prostate cancer treated with radiotherapy may have improved overall survival without negatively affecting quality of life, according to long-term results from a recent trial.

These findings, which were detailed in the journal PLoS Medicine, may confirm that treatment with radiotherapy should be considered standard of care for this patient population.

“The magnitude of the survival benefit is substantial and clinically relevant, particularly given that prostate (radiotherapy) is a relatively cheap, widely accessible and well-tolerated treatment,” the researchers wrote in the paper.

To conduct the STAMPEDE trial, researchers analyzed data from 2,061 men with newly diagnosed metastatic prostate cancer. Patients were assigned to either standard of care alone (1,029 patients; median age, 68 years) or standard of care plus radiotherapy (1,032 patients; median age, 68 years). Standard of care was the same in both groups and included lifelong hormone therapy.

Most patients in the study (1,939 patients) had their metastatic prostate cancer burden classified by imaging modalities and defined as either high (cancer spread to several sites throughout the body) or low (cancer spread to one or two locations). Of these patients with classifiable burden, 42% were defined as having low burden and 58% had high burden.

The primary focus of this study was to assess overall survival (time from treatment assignment to all-cause death). Quality of life was also monitored throughout the study. Patients were followed up for at least five years for a median of 61.3 months.

Standard of care with radiotherapy, compared with standard of care alone, improved overall survival in patients with low metastatic burden (156 deaths versus 202 deaths, respectively), although this did not occur in patients with high metastatic burden (386 deaths versus 375 deaths). The time to symptomatic local events such as acute kidney injury, urinary tract obstruction or urinary tract infection did not differ between the two treatment groups.

“This final analysis (of the STAMPEDE trial) has confirmed that prostate radiotherapy improves overall survival in men with newly diagnosed, low-burden metastatic prostate cancer, but not in men with high-burden disease,” the authors wrote.

Both treatment groups also had similar quality of life factors including social, psychological and physical functions.

Long-term severe or worse urinary toxicity occurred in 10 patients assigned standard of care alone and 10 patients assigned both standard of care and radiotherapy. In addition, long-term severe or worse bowel toxicity was reported by 15 patients in the standard of care group and 11 patients in the standard of care plus radiotherapy group.

One limitation of the study was the fact that patients were recruited between 2013 and 2016, during which several advances were made in the area regarding imaging and treatment.

“Standard treatment for men with low-burden metastatic disease now includes one of the newer hormone agents … in addition to (androgen deprivation therapy),” the researchers wrote. “The effects of these agents on the survival benefit of prostate (radiotherapy) is unknown. Similarly, the effect of prostate (radiotherapy) on the survival benefit of the newer hormonal agents is also unknown. Based on current evidence, it is reasonable to assume that both prostate (radiotherapy) and one of the newer hormonal agents should be considered (standard of care) for low-burden metastatic disease in addition to (androgen deprivation therapy).”

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