In a retrospective case series reported in JAMA Network Open, Poon et al found that definitive stereotactic body radiotherapy (SBRT) was associated with good long-term overall survival and delayed widespread disease progression—but “modest” progression-free survival—in adults with extracranial oligometastasis.
The study involved 1,033 patients consecutively treated at the Sunnybrook Odette Cancer Centre of the University of Toronto, University of Florida, Johns Hopkins University, Princess Alexandra Hospital at the University of Queensland, University of Turin, and the University Hospitals Cleveland Medical Center between January 2008 and December 2016. Patients had to have five or fewer extracranial oligometastases and had to have received curative treatment for primary tumors.
Time to widespread progression was defined as time to further metastatic dissemination not amenable to any further local ablative therapy, including development of at least six new sites of extracranial metastasis or malignant effusions.
Overall, 1,416 SBRT courses were performed in patients with one (n = 596; 57.7%), two (n =245; 23.7%), three (n = 105; 10.2%), four (n = 55; 5.3%), or five oligometastases (n =32; 3.1%). Median follow-up was 24.1 months (range = 0.3–104.7 months).
Median overall survival was 44.2 months (95% confidence interval [CI] = 39.2–48.8 months), with 1-, 3-, and 5-year rates of 84.1%, 56.7%, and 35.2%. Median time to widespread progression was 42.5 months (95% CI = 36.8–53.5 months), with 1-, 3-, and 5-year rates of 24.6%, 45.2%, and 54.5%.
Median progression-free survival was 12.9 months (95% CI = 11.6–14.2 months), with 1-, 3-, and 5-year rates of 52.1%, 23.0%, and 14.8%. At the time of first progression, 342 patients (33.1%) had recurrence of oligometastatic disease, with 230 (22.3%) undergoing subsequent ablative therapies at all identified metastatic sites.
Factors significantly associated with overall survival on multivariate analysis consisted of: primary tumor type (hazard ratios [HRs] vs prostate as reference group = 3.73, P < .001, for breast; 5.75, P < .001, for colorectal; 4.67, P < .001, for kidney; 10.61, P < .001, for lung; and 12.00, P < .001, for other); metachronous oligometastasis more than 24 months since initial diagnosis (HR = 0.63, P < .001); metastasis confined to the lung (HR = 0.58, P < .001); and nodal or soft-tissue metastasis only (HR = 0.49, P = .02).
The investigators concluded, “This study found favorable long-term overall survival and widespread progression rates associated with extracranial oligometastases ablated with SBRT; however, modest progression-free survival rates were observed. A substantial proportion of patients with oligometastasis developed progressive disease and were treated with local ablation. Factors that can inform clinical decision-making and clinical trial design include primary tumor type, a metachronous presentation more than 24 months since diagnosis, and the site of oligometastasis presentation.”
Ian Poon, MD, of the Sunnybrook Odette Cancer Centre, University of Toronto, is the corresponding author for the JAMA Network Open article.
Disclosure: The study was supported by a grant from Elekta AB. For full disclosures of the study authors, visit jamanetwork.com.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.