P01.092 Salvage Frameless Stereotactic Radiosurgery as first treatment option for recurrent brain metastases. May durable intracranial control be achieved?

Abstract

BACKGROUND: Frameless Stereotactic Radiosurgery (FL-SRS) is a feasible procedure for the management of brain metastases (BM), delivering a single large radiation dose to a well-defined target. We aimed to assess its role as a first treatment option in recurrent brain metastases (r-BM) previously treated with SRS, WBRT or metastasectomy with or without radiation. MATERIAL AND METHODS: Patients (p) were immobilised with a thermoplastic mask and individualised dental mould. Radiation techniques (arch-therapy, IMRT or VMAT) were selected depending on location, shape and size of the lesion. Treatment was delivered with a linac equipped with FFF, Cone beam-CT and HEXAPOD system. PTV was defined as GTV plus 1,5-2mm margin. The total dose (18-36Gy) was prescribed to 95% of the PTV in 1-5 fractions. RESULTS: Between October 2014 and April 2017, 28 patients with 98 r-BM were treated. Primary tumor distribution was: NSCLC (11p, 39%), breast cancer (7p, 25%) and other tumor histologies (10p, 36%). A median of 3 r-BM were treated per patient with a median prescribed dose of 18,88 Gy. The median PTV volume was 1,00cc. Nineteen (68%) patients were previously treated with SRS, 6p (21%) received WBRT, 2p (7%) underwent metastasectomy plus irradiation of the surgical bed and 1p (4%) metastasectomy alone. Fourty-three percent of r-BM showed radiological response. Local progression was observed in 8 r-BM (8%) and the local-failure free-survival was 86% at 1-year and 73% at 2-years. Distant brain failure was recorded in 13p (46%). With a median follow up of 19 months, the median OS has not been reached, brain-PFS and OS at 1-year and 2 years were 70% - 52% and 29% - 35%, respectively. Twelve BM developed signs of radionecrosis (12%) and 2 out of 7p were symptomatic requiring an active treatment. Only one patient died due to a neurological cause. CONCLUSION: FL-SRS is a precise, feasible and effective first option treatment for r-BM. Despite the poor prognosis in this subgroup of patients, our data show excellent local control and long-term survivors with very low rates of toxicity.