Retrospective study of the efficiency and the tolerance of the association of immunotherapy and cerebral stereotactic radiotherapy in patients with metastatic melanoma: analysis of the clinical, radiological and histological associated factors

Immunotherapy (IT) made the proof of its efficiency in metastatic melanoma. The association of IT and cerebral stereotactic radiotherapy (SRT) may have both a cerebral and extra-cerebral control. The aim of our study was to estimate the efficiency of the association of IT and cerebral SRT in metastatic melanoma. We conducted a single-center retrospective study of patients with cerebral and extra-cerebral metastatic melanoma, wild BRAF, treated with concurrent IT anti CTLA-4 or anti PD-1 and cerebral SRT from 2013 to 2017. Tumor response was determined using the RECIST v1.1.criteria. We included 14 patients with a total of 44 irradiated cerebral targets lesions and 22 evaluated extra-cerebral targets lesions. Extra-cerebral progression after SRT was 5,1 months (interquartile range 2,9-18,6 months). Overall survival was 24,6 months. Extra-cerebral progress after cerebral SRT seemed to be better in patients with local response to SRT (8,5 months versus 3,8 months, p=0,17). It seemed also to be better with 4 or more irradiated cerebral metastases and did not seem to be different according to DS-GPA score, irradiated maximal tumor volume, PD-L1 expression and neurological symptoms. However this results are not statistically significant given to the small cohort. We observed five grade 3 and 4 toxicity, one radiation necrosis and one cerebral hemorrhage. We report extra-cerebral data after cerebral SRT in BRAF savage metastatic melanoma treated with concurrent immunotherapy and cerebral SRT and suggest a better extra-cerebral answer in patients with local response to SRT. Prospective studies are warranted to validate these results. (author)