Outcome of metastatic melanoma following immune checkpoint inhibitor treatment by tumor infiltrating lymphocyte of primary cutaneous site.

Abstract

e22005 Background: TIL include antigen specific clonal T cells responding to tumor antigens (TA) in the tumor microenvironment. Biological relevance of TIL at the PCM following ICI treatment of MM is not clear. Since there is overlap of TA between primary and its metastasis, we hypothesized that TIL at PCM site may serve as a biomarker of response to ICI treatment of MM. Methods: We did a retrospective analysis of MM patients (pts.) receiving ICI treatment between 2012 and 2019 following an IRB approved protocol. Response and survival at 12, 24 and 36 months (mths) was correlated with PCM site TIL. Pts. who received at least one dose of ICI for MM were eligible and those with metastasis from unknown PCM, received anti-BRAF treatment or lacked information on TIL at PCM were excluded. Pts. were stratified as group (gr.) A, B and C representing brisk, non-brisk and absent TIL respectively. Responses defined by RECIST criteria (response, no response, stable disease) as well as overall survival calculated from time of initiation of ICI to death from any cause (OS) at 12, 24 and 36 mths was correlated to TIL at PCM. Results: 42 pts. received ICI for MM between 2012-2019 meeting the eligibility criteria. Median age is 68 years (yrs.) (63, 71 and 73 yr. respectively for group A, B and C), 27 male, 15 women. The median thickness of PCM was 3.5, 3.75 and 4.75 mm in group A, B and C respectively. 11 of 14, 9 of 16 and O of 12 pts. responded to ICI while 2, 5, 14 and 1,2, 0 patients showed no response and stable disease respectively. O.S. at 12, 24, and 36 mths. was 12/14, 11/16 and 1/12 pts.; 10/14, 7/16, 0/12 pts. and 8/14, 6/16 and 0/12 pts. respectively in three groups. Conclusions: Brisk and absent TIL correlated with favorable and unfavorable response to ICI treatment of MM while non-brisk TIL showed intermediate outcomes. Larger data set could help validate our findings.