Fractionated stereotactic radiotherapy to the post-operative cavity for radioresistant and radiosensitive brain metastases

Following surgical resection for brain metastases, fractionated stereotactic radiotherapy (FSRT) has been used as an alternative to single dose treatment for large cavities and to reduce risks of late toxicity. The purpose of this study was to evaluate the outcomes of patients treated with FSRT to the post-operative bed for both radioresistant and radiosensitive brain metastases. Between December 2009 and May 2013 a total of 65 patients with newly diagnosed brain metastases were treated with resection followed by FSRT. Patients were treated to a total dose of 20–30 Gy in five fractions. Median planning target volume (PTV) was 16.88 cm³ (range 4.87–128.43 cm³). The median follow-up for all patients was 8.5 months (range 1.1–28.6 months) with a median of 12.9 months for living patients. One and two year Kaplan–Meier estimates of local control were 87.0 and 70.0 %, respectively. Local control at 1 year was 85.6 and 88.0 % for radioresistant and radiosensitive tumors, respectively (p = 0.44). A PTV ≥17 cm³, was associated with local failure, HR 8.63 ((1.44–164.78); p = 0.02). One and two year distant control rates were 50.9 and 46.2 %, respectively with six patients (9.2 %) experiencing leptomeningeal disease. OS rates at 1 and 2 years were 65.2 and 47.5 %, respectively. Survival was significantly associated with recursive partitioning analysis class (p = 0.001) and graded prognostic assessment score (p = 0.005). One case of radionecrosis was noted on follow-up imaging. FSRT in five fractions offers excellent local control in both radiosensitive and radioresistant tumors with minimal toxicity.