Baseline tumor-infiltrating lymphocyte patterns and response to immune checkpoint inhibition in metastatic cutaneous melanoma

Introduction The presence of tumor-infiltrating lymphocytes (TILs) in melanoma has been linked to survival. Their predictive capability for immune checkpoint inhibition (ICI) response remains uncertain. Therefore, we investigated the association between treatment response and TILs in the largest cohort to date and analyzed if this association was independent of known clinical predictors of response. Methods In this multicenter cohort study, patients who received first-line anti-PD1 ± anti-CTLA4 for advanced cutaneous melanoma were identified. TILs were scored as absent, non-brisk or brisk on hematoxylin and eosin (H&E) slides of primary melanoma and pre-treatment metastases. Scoring systems evaluating the infiltration and intensity patterns (MIA-score) and the percentage of stromal TILs were also evaluated. The primary outcome was objective response rate (ORR), with PFS and OS being secondary outcomes. Univariable and multivariable logistic regression and Cox proportional hazard regression analyses were performed, adjusting.for age, sex, disease stage, ICI type, BRAF mutation, lactate dehydrogenase (LDH) level and WHO performance score. Results Metastatic melanoma specimens were available for 650 patients and primary specimens from 565 patients.. No association was found between TILs in primary melanoma specimens and response. In metastatic specimens, patients with non-brisk TILs (aOR 1.56, 95% CI 1.06-2.29) and brisk TILs (aOR 3.28, 95% CI 1.72-6.56) had a higher probability of response, longer median PFS (9.2 and 19.4 vs. 6.5months [p=0.009]) and median OS (49.5 and 40.9 vs 21.3 months [p=0.007]) when compared to absent TILs. Similar results were noted using the MIA- and stromal TIL scores. Conclusion In advanced melanoma patients, TIL patterns on H&E slides of pre-treatment metastases are associated with ICI response. This is independent of known clinical predictors. TILs are easily scored on readily available H&Es, which facilitates the use of this biomarker for ICI outcomes in clinical practice. ### Competing Interest Statement Conflicts of interests Dr. De Groot has advisory board relationships with BMS. Dr. Aarts has advisory board / consultancy honoraria from Amgen, Bristol Myers Squibb, Novartis, MSD-Merck, Merck-Pfizer, Pierre Fabre, Sanofi, Astellas, Bayer and received research grants from Merck-Pfizer and all were paid to the institution and not related to current work. Dr. Hospers has consultancy/advisory relationships with Amgen, Bristol Myers Squibb, Roche, MSD, Pfizer, Novartis, Sanofi and Pierre Fabre and has received research grants from Bristol Myers Squibb and Seerave and all were paid to the institution. Dr. Kapiteijn has consultancy/advisory relationships with Bristol Myers Squibb, Novartis, Merck, Pierre Fabre, Lilly and Bayer not related to current work and paid to institute, and received research grants not related to this paper from Bristol Myers Squibb, Delcath and Pierre-Fabre. Dr. Piersma had advisory board relationships with BMS, Novartis and Pierre Fabre, honoraria were paid to institution. Dr. Suijkerbuijk has consulting/advisory relationships with Bristol-Myers Squibb, Merck Sharp and Dome, Abbvie, Pierre Fabre Novartis, Sairopa, received honoraria from Novartis, Roche, Merck Sharp and Dome and received research funding from TigaTx, Bristol Myers Squibb and Philips and all were paid to institution and not related to the study. Dr. Schrader received honoraria/research funding from Kyowa Kirin paid to the institution and not related to the study. The remaining authors of this manuscript have no conflicts of interest to disclose. ### Funding Statement This research was funded by The Netherlands Organization for Health Research and Development (ZonMW, project number 848101007), by an unrestricted grant of Stichting Hanarth Fonds, The Netherlands, and by Philips. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: After review by the Medical Research Ethics Committee (NedMec, Utrecht, The Netherlands), this study was deemed not subject to the Medical Research Involving Human Subjects Act in accordance with Dutch regulations. Informed consent was waived. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Due to confidentiality agreements, clinical and imaging data cannot be made available.