In the first randomized, phase II clinical trial of its kind, researchers have shown that an aggressive form of high-precision radiation therapy can greatly increase how long oligometastatic patients live and double how long they live without cancer.

The findings will be presented in a news briefing and the plenary session at the 60th Annual Meeting of the American Society for Radiation Oncology (ASTRO) next week.

Generally, when a patient has cancer that has spread to other parts of the body called metastatic cancer they are considered incurable. This multi-center trial challenged this idea by studying patients with a variety of oligometastatic cancers that is, cancers that had been previously treated but then returned in a limited number of other parts of the body.

Stereotactic ablative radiotherapy

The patients were treated with stereotactic ablative radiotherapy (SABR), also known as stereotactic body radiation therapy (SBRT), which is a form of high-precision cancer therapy that delivers substantially higher doses of radiation to the tumor site in just one or a few treatment sessions.

"Traditionally, when a patient had cancer that spread to other parts of their body such as to their bones or brain they were considered to be incurable," said David Palma, MD, lead author a researcher at Lawson Health Research Institute, the research institute of London Health Sciences Centre (LHSC) and lead institution of the multi-center study.

"But there is a theory called the oligometastatic theory that if a patient only has a few spots of cancer returning, those spots could be killed with radiation or surgery to improve their survival," said Palma.

"Now, we have been able to show, for the first time in a randomized trial, that high-dose radiation can effectively treat these limited recurrences, and we've been able to increase survival by a median of 13 months," said Palma.

In this randomized, phase II, an open-label study called SABR-COMET, Dr. Palma and his colleagues enrolled 99 patients from four countries (Canada, Scotland, the Netherlands and Australia).

Each patient had been treated for cancer, but cancer had returned, with tumors appearing in as many as five different places. All patients had a good performance status (ECOG 0-1) and a life expectancy of more than six months.

Patients had been diagnosed with a wide range of cancer types, most commonly breast (n=18), lung (n=18), colon or rectum (n=18) and prostate (n=16) cancers. In most patients (n=92), cancer had spread to one to three new sites.

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% of the patients were men. No baseline patient characteristics were significantly different between the two treatment arms. Median follow-up time was 27 months.