Role of tumor-infiltrating lymphocytes in melanoma prognosis and treatment strategies: A systematic review and meta-analysis

Purpose: Numerous studies underscore the relevance of tumor-infiltrating-lymphocytes (TILs) as important prognostic factors for melanoma. This meta-analysis aims to provide a comprehensive literature overview elucidating their role in predicting patient outcomes, specifically investigating the association between TIL density and prognosis. Methods: From an initial pool of 6094 records, 16 met the eligibility criteria, encompassing a collective cohort of 16021 patients. Data on TIL counts, clinical characteristics, and survival metrics (5-year overall survival [5yOS], 10-year overall survival [10yOS], and 5-year melanoma-specific survival [5yMSS]) were extracted from each study and expressed as proportions. Results were graphically presented using forest plots, reporting the estimates from individual studies, summary estimates, and corresponding 95 % confidence intervals (CI). Results: Analysis revealed a statistically significant difference in 5yOS concerning subgroup differences However, 10yOS and 5yMSS did not exhibit statistical significance. Nonetheless, a consistent trend emerged indicating a higher survival rate corresponding to increased immune cell density, ranging from absent TILs to brisk levels. Conclusions: TILs present potential as a readily applicable prognostic factor. Yet, further investigations into their density and phenotypic subpopulation characteristics could enhance our understanding of their predictive value in tailoring optimal patient-specific therapies.