Salvage whole brain radiotherapy or stereotactic radiosurgery after initial stereotactic radiosurgery for 1–4 brain metastases

Patients with limited brain metastases are often candidates for stereotactic radiosurgery (SRS) or whole brain radiotherapy (WBRT). Among patients who receive SRS, the likelihood and timing of salvage WBRT or SRS remains unclear. We examined rates of salvage WBRT or SRS among 180 patients with 1–4 newly diagnosed brain metastases who received index SRS from 2008–2013. Competing risks multivariable analysis was used to examine factors associated with time to WBRT. Patients had non-small cell lung (53 %), melanoma (23 %), breast (10 %), renal (6 %), or other (8 %) cancers. Median age was 62 years. Patients received index SRS to 1 (60 %), 2 (21 %), 3 (13 %), or 4 (7 %) brain metastases. Median survival after SRS was 9.7 months (range, 0.3–67.6 months). No further brain-directed radiotherapy was delivered after index SRS in 55 % of patients. Twenty-seven percent of patients ever received salvage WBRT, and 30 % ever received salvage SRS; 12 % of patients received both salvage WBRT and salvage SRS. Median time to salvage WBRT or salvage SRS were 5.6 and 6.1 months, respectively. Age ≤60 years (adjusted hazard ratio [AHR] = 2.80; 95 % CI 1.05–7.51; P = 0.04) and controlled/absent extracranial disease (AHR = 6.76; 95 % CI 1.60–28.7; P = 0.01) were associated with shorter time to salvage WBRT. Isolated brain progression caused death in only 11 % of decedents. In summary, most patients with 1–4 brain metastases receiving SRS never require salvage WBRT or SRS, and the remainder do not require salvage treatment for a median of 6 months.