Between February 2012 and August 2016, the patients were randomized at a 1:2 ratio into two treatment arms: palliative standard of care treatments (SOC) and SOC plus stereotactic radiation therapy for all metastatic lesions. The median patient age was 68 years (range=43-89), and 59 percent of the patients were men. No baseline patient characteristics were significantly different between the two treatment arms. Median follow-up time was 27 months.

Patients who received SABR treatments lived considerably longer than those who did not. Median overall survival was 41 months (95 percent Confidence Interval: 26 months, upper limit not reached) for patients given stereotactic radiation, compared to 28 months (95% CI: 19, 33 months) in the standard treatment arm (stratified log rank p=0.09). This phase II trial was designed to look for a signal, defined as a p-value less than 0.20, as an initial comparison of these two treatment groups.


Stereotactic radiation also doubled the time patients lived without cancer growth. Progression-free survival was 12 months (95% CI: 6.9, 30 months) in the stereotactic radiation arm, compared to six months (95% CI: 3.4, 7.1 months) for those who received standard radiation therapy (p=0.001).

"We were surprised and quite pleased. We didn't expect t survival benefit to be quite so long for patients with metastatic disease," said Dr. Palma, also a clinician-scientist at the Ontario Institute for Cancer Research, which provided funding for this study.

Being treated with stereotactic radiation resulted in more negative side effects than standard treatments. Just 9 percent of patients who received standard treatments experienced serious adverse events (grade 2 or higher), while 30 percent of those in the SABR arm did (p=0.022). The most common negative side effects were fatigue (n=10), dyspnea, or difficulty breathing (n=9), muscle and joint pain (n=7), bone pain (n=6) or pain not otherwise specified (n=7). Three patients in the experimental arm died due to adverse events -- one from a pulmonary abscess and one from subdural hemorrhage after surgery to repair a SABR-related perforated gastric ulcer and one from radiation pneumonitis. While such events can occur with standard radiation therapy, they are rare.

"Stereotactic radiation therapy needs to be delivered carefully and by an experienced team, and there is a small risk of very serious side effects, as well as mortality. But overall, for patients whose cancers have spread, and who are not expected to survive otherwise, the overall survival benefit of SABR appear to outweigh these risks," said Dr. Palma.

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