Cancer that spreads from an original tumour to other parts of the body is generally considered incurable. In an international study led by Lawson Health Research Institute, the research institute of London Health Sciences Centre (LHSC), researchers challenged this idea by showing that high-dose radiation can improve survival in patients with cancer that has spread to five or less sites.
The study called SABR-COMET was the first randomized phase II clinical trial of its kind. It included 99 patients with oligometastatic cancer – cancer that has metastasized or spread to a limited number of sites in the body. In particular, SABR-COMET patients were those previously treated for cancer that had returned in up to five different places in the body. Research participants were recruited from across Canada, Australia, the Netherlands and Scotland, including 51 patients from LHSC’s London Regional Cancer Program.
The study examined the use of stereotactic ablative radiotherapy (SABR) to improve patient outcomes. SABR is a technique that precisely delivers radiation to a tumour in substantially higher doses than normal with the goal of destroying cancerous cells. Patients were randomly selected to receive either standard treatment, consisting of chemotherapy or radiation therapy, or standard treatment combined with SABR to target every known tumour in a patient’s body.
The research team found that patients who received SABR lived longer than patients who did not. Median survival for patients who received SABR was 41 months compared to 28 months for those who received standard treatment. SABR also doubled the amount of time patients lived without further cancer growth - a median of 12 months for patients receiving SABR and six months for those not. After five years, 46 per cent of patients treated with SABR were still alive compared to 24 per cent of those who received standard treatment.
“In the past, the spread of lung cancer to the bones or breast cancer to the brain was considered incurable,” says Dr. David Palma, lead author on the study, researcher at Lawson and radiation oncologist at LHSC. “We’ve shown for the first time that if cancer has spread to only a few spots, we can target those tumours with high-dose radiation to increase how long a patient lives.”
There were no differences in quality of life between patients treated with SABR and those who received standard treatment, but SABR was associated with more negative side effects. Thirty per cent of patients who received SABR experienced serious side effects compared to nine percent of patients who received standard treatment. The most common side effects included fatigue, difficulty breathing, muscle and joint pain, and bone pain.
“SABR needs to be delivered carefully and by an experienced team. While there is a small risk of very serious side effects, these are patients with limited options,” says Dr. Palma, also a clinician-scientist at the Ontario Institute for Cancer Research (OICR) which funded the study. “Ultimately, the decision to offer SABR is up to the patient’s oncologist. Physicians should at least consider it as a treatment option for oligometastatic patients.”
Dr. Palma notes that some patients receiving SABR developed additional tumours during the trial. Those additional tumours could sometimes be targeted and successfully treated. Because of this success, the research team is now planning a follow-up study that will assess the use of SABR in patients with cancer that has spread to up to ten sites. The study, called SABR-COMET-10, is anticipated to launch by early 2019 and will be supported locally by London Health Sciences Foundation (LHSF).
“We are very excited about the potential for this research to afford cancer patients longer and higher quality of life,” says Neil Johnson, Regional Vice President, Cancer Services at LHSC. “This illustrates the critical partnership of clinicians, scientists and patients in driving translational research.”
Results from SABR-COMET will be shared by Dr. Palma at the 60th Annual Meeting of the American Society for Radiation Oncology (ASTRO) on October 22, 2018. The study received funding from OICR and a London Regional Cancer Program Catalyst Grant, supported by donors through LHSF.
