Introduction: Immune checkpoint inhibitors (ICIs) have revolutionized melanoma treatment. However, only one third of patients achieve durable disease control and long-term survival. Treatment is costly and associated with novel immune related adverse events. Therefore, there is an urgent need for predictive biomarkers to better select patients most suited to treatment with ICIs. Tumour infiltrating lymphocytes (TILs) is a favorable prognostic marker in different tumour types. We therefore evaluated the predictive significance of TILs and regression in primary cutaneous melanoma and correlated it with response to ICI therapy.
Patients & Methods: Patients treated with ICI therapy between Feb 2015-June 2016 for advanced melanoma were identified from institutional database. Data was collected from electronic medical records and Cancer Registry with a censor date of 1st June 2016. Survival was calculated through Kaplan-Meir analysis. Overall survival (OS) and progression free survival (PFS) was calculated from start of therapy till date of death/last follow up & date of progression/death respectively.
Results: 35 patients were identified that fulfilled selection criteria. Regression and TILs were reported in the primary pathology of 21 patients. Patients with TILs in their primary pathology had a trend towards improved outcome with ICI for both PFS (6m vs 2.5m, log-rank P=0.052) and OS (NR vs 3m, p=0.2) compared to those with no TILs. There was no difference in PFS or OS for those with or without regression.
Conclusion: TILs in primary cutaneous melanoma could be a useful predictor of response to ICI therapy and needs to be further evaluated prospectively in larger studies.