Patients with resected brain metastases who underwent stereotactic radiosurgery (SRS) had lower rates of local recurrence compared with observation alone, according to the results of a phase III trial published in Lancet Oncology.
“Our results suggest that SRS might be an alternative to whole brain radiotherapy for patients after surgical resection of one to three brain metastases,” wrote Anita Mahajan, MD, of the department of radiation oncology at the University of Texas MD Anderson Cancer Center in Houston, and colleagues. “Future trials should explore increased radiation doses to improve local control and report outcomes with respect to quality of life.”
Whole brain radiotherapy (WBRT) is the standard of care after surgical resection of brain metastases, but the treatment is associated with cognitive deficits. According to the study, “many physicians have advocated the use of SRS after surgical resection to improve local control and avoid the cognitive side effects of WBRT.”
With this study, Mahajan and colleagues evaluated if SRS improved local recurrence after surgical resection compared with observation. The single-center trial included 132 patients who had complete resection of one to three brain metastases, a Karnofsky score of 70 or higher, and were able to have an MRI scan. Patients were randomly assigned to either SRS of the resection cavity or observation. The primary endpoint was time to local recurrence in the resection cavity.
The median follow-up was 11.1 months. Among patients who underwent observation, 48% developed local recurrence compared with 24% of patients in the SRS group.
The 12-month freedom from local recurrence was 43% in the observation group compared with 72% in the SRS group (hazard ratio, 0.46; 95% CI, 0.24–0.88; P = .015). These data confirm that “surgical resection of brain metastases is insufficient to provide durable local control,” the researchers wrote.
Patients assigned to observation had a median time to local recurrence of 7.6 months; the median time to recurrence was not reached in patients assigned to SRS.
Median overall survival was similar between the two groups (18 months for observation vs 17 months for SRS).
“Despite our finding that local control is improved after SRS compared with observation, overall survival was similar for both groups,” the researchers wrote. “The higher survival could be because our study was done at a tertiary cancer center and could also reflect improvements in systemic treatments.”
The researchers conducted a post-hoc analysis to see if tumor size was associated with outcomes. The 12-month freedom from local recurrence was 91% in patients with tumors with a diameter up to 2.5 cm, was 40% for tumors between 2.5 to 3.5 cm, and 46% in tumors greater than 3.5 cm in diameter.
“This suggests that small tumors that have been resected could instead be put under surveillance without additional treatment after resection; however, in the post-hoc analysis, SRS to lesions less than 2.5 cm showed a higher freedom from local recurrence than did observation, suggesting that even these smaller tumors might benefit from SRS after resection,” the researchers wrote.
No adverse events of treatment-related deaths occurred in either group.