Objective: The authors investigated and compared the results of staged stereotactic radiosurgery (S-SRS) alone and those of postoperative cavity SRS (C-SRS) for patients with midsize-to-large brain metastases (BMs).
Methods: Patients with BMs who had undergone S-SRS or C-SRS during the period from 2010 to 2020 were retrospectively identified from an institutional database. The two treatment groups were generated by propensity score matching (PSM; match ratio 2:1) based on 13 potential prognostic covariates: sex, age, Karnofsky Performance Status, type of primary cancer, timing of BM diagnosis, extracranial disease status, driver mutations, molecular target therapy, neurological symptoms, number of BMs, location of BMs treated with S-SRS or C-SRS, maximal tumor or cavity volume, and cumulative intracranial tumor volume. Patient survival and control of intracranial disease were compared between the S-SRS and C-SRS groups using time-dependent analyses taking into account competing events.
Results: In total, 110 patients in the S-SRS group and 62 in the C-SRS group were selected by PSM. In the S-SRS group, the median interval between the two radiosurgical sessions was 21 days, and the median total prescription dose was 28 Gy at 50%. In the C-SRS group, the median time from surgery to C-SRS was 16 days, and the median prescription dose delivered to the surgical cavity was 15 Gy at 55%. At the time point of data set fixation, 129 patients had died, 43 were alive, and none had been lost to follow-up. The 2-year survival rates for the S-SRS and C-SRS groups after the initial intervention were 33% and 37% and the median survival times were 14.8 and 17.5 months, respectively (p = 0.33). The 2-year cumulative neurological mortality rates were 11% and 9%, respectively (p = 0.65). The 2-year local failure rates were 32% and 12% (p = 0.036) and the 2-year distant recurrence rates were 55% and 58%, respectively (p = 0.53). The 2-year leptomeningeal disease development rates were 9% and 25%, respectively (p = 0.007).
Conclusions: The present study revealed no significant difference in overall survival or cumulative neurological mortality between the S-SRS and C-SRS groups. The local control failure rate was significantly higher in the S-SRS group, whereas the incidence of leptomeningeal disease development was significantly higher in the C-SRS group.
Keywords: Gamma Knife; brain metastases; oncology; postoperative cavity radiosurgery; propensity score matching analysis; resection; staged radiosurgery; stereotactic radiosurgery.