Frequency and prognostic role of tumor infiltrating lymphocytes and MMR status in advanced non-colorectal GI malignancies.

Abstract

89 Background: Tumor infiltrating lymphocytes (TILs) and mismatch repair gene mutation (MMR) status are emerging biomarkers in immunotherapy. MMR status and TILs have significant clinical implications with respect to treatment with checkpoint inhibitors. We designed a study to determine the frequency and prognostic utility of TILs and MMR in advanced unresectable non-colorectal GI (NCGI) cancers. Methods: This is a retrospective cohort study of patients who were diagnosed with metastatic or unresectable NCGI cancers between 2009 and 2015 at St. John Hospital and Medical Center. Immunohistochemistry panels were performed on representative tissue sections for MMR testing. TILs were assessed on the hematoxylin and eosin stained slide of the same tissue section. MMR was interpreted as deficient (d) or proficient and TILs were categorized as ≤5 or > 5 per high power field. Descriptive statistics were generated using frequency distributions, medians and means. Kaplan-Meier analysis was performed to determine the impact of TILS and MMR on survival; differences by factor were assessed with the Log_Rank test. Results: We analyzed 132 patients; the mean age at diagnosis was 66.7 years, 62.1% were male. All samples had proficient MMR status. The percentage of patients with TILs ≤ 5 was 46.2. There was no statistically significant difference in median overall survival (OS) by TILs when stratified by stage of tumor. When stratified by type of tumor, median OS by TILs level was significantly different only for hepatocellular cancers (HCC) (≤ 5 TILs, 86 days vs. > 5 TILs 312 days, p = 0.031), table 1. Conclusions: Our study suggests that MMR-d tumors are quite rare in advanced NCGI malignancies. TILs can be present in tumor microenvironment of NCGI malignancies. Though the number of patients in our study was small, there was a statistically significant difference in median OS of patients with HCC when stratified by TILs status.[Table: see text]