Long duration of immunotherapy before radiosurgery might improve intracranial control of melanoma brain metastases.

ABSTRACT

PURPOSE: Despite significant advances that have been made in management of metastatic melanoma with immune checkpoint therapy, optimal timing of combination immune checkpoint therapy and stereotactic radiosurgery is unknown. We have reported toxicity and efficiency outcomes of patients treated with concurrent immune checkpoint therapy and stereotactic radiosurgery. PATIENTS AND METHODS: From January 2014 to December 2016, we analyzed 62 consecutive patients presenting 296 melanoma brain metastases, treated with gamma-knife and receiving concurrent immune checkpoint therapy with anti-CTLA4 or anti-PD1 within the 12 weeks of SRS procedure. Median follow-up time was 18 months (mo) (13-22). Minimal median dose delivered was 18 gray (Gy), with a median volume per lesion of 0.219 cm3. RESULTS: The 1-year control rate per irradiated lesion was 89% (CI 95% 80.41-98.97). Twenty-seven patients (43.5%) developed distant brain metastases after a median time of 7.6 months (CI 95% 1.8-13.3) after gamma-knife. In multivariate analysis, positive predictive factors for intracranial tumor control were delay since the initiation of immunotherapy exceeding 2 months before gamma-knife procedure (P=0.003) and use of anti-PD1 (P=0.006). Median overall survival (OS) was 14 months (CI 95% 11-NR). Total irradiated tumor volume<2.1 cm3 was a positive predictive factor for overall survival (P=0.003). Ten patients (16.13%) had adverse events following irradiation, with four grade≥3. Predictive factors of all grade toxicity were female gender (P=0.001) and previous treatment with MAPK (P=0.05). CONCLUSION: A long duration of immune checkpoint therapy before stereotactic radiosurgery might improve intracranial tumor control, but this relationship and its ideal timing need to be assessed in prospective trials.