Stereotactic ablative radiotherapy (SABR) can greatly increase how long oligometastatic patients survive and doubles how long they live without cancer, according to new research presented at this week's American Society for Radiation Oncology (ASTRO) meeting.
The multicenter trial studied patients with a variety of oligometastatic cancers -- cancers that were treated but then returned in a limited number of other parts of the body. The patients were treated with SABR, also known as stereotactic body radiation therapy (SBRT), a form of high-precision cancer therapy that delivers substantially higher doses of radiation to the tumor site in one or a few treatment sessions.
The randomized, phase II, open-label study was known as Stereotactic Ablative Radiotherapy for Comprehensive Treatment of Oligometastatic Tumors (SABR-COMET). Dr. David Palma, PhD, lead author and researcher at Lawson Health Research Institute, and colleagues enrolled 99 patients from Canada, Scotland, the Netherlands, and Australia. Each patient had been treated for cancer but the cancer had returned, with tumors appearing in as many as five different places. All patients had good performance status (ECOG 0-1) and a life expectancy of more than six months.
The researchers found that high-dose radiation can effectively treat limited recurrences of cancer and increase survival by a median of 13 months. Patients were diagnosed with a wide range of cancer types, most commonly breast, lung, colon or rectum, and prostate cancers. In most patients, the 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 and standard of care plus stereotactic radiation therapy for all metastatic lesions. The median patient age was 68 and 59% were men. No baseline patient characteristics differed significantly between the two treatment arms. The 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 for patients given stereotactic radiation, compared with 28 months in the standard treatment arm.
Stereotactic radiation also doubled the time patients lived without cancer growth. Progression-free survival was 12 months in the stereotactic radiation arm, compared with six months for those who received standard radiation therapy.
Nearly half (46%) of the patients treated with stereotactic radiation were still alive after five years, compared with 24% of those who received standard care, a result that may encourage physicians to consider SABR as a treatment option, according to Palma.
"Ultimately, the question of whether an oncologist will offer this treatment as the standard of care for oligometastatic patients will be up to that oncologist," he said in a statement from ASTRO. "At the very least, physicians should be considering this as a treatment option for their patients."
