Coexistence of regression and tumor infiltrating lymphocytes is associated with more favorable survival in melanoma

Advances in Tumor-Infiltrating Lymphocyte (TIL) as a Prognostic Factor and for Treating Invasive Cutaneous Melanoma

Invasive cutaneous melanoma is responsible for about 5% of skin tumors yet is liable for nearly 70% of skin cancer-related deaths. Despite notable advancements over the past decade, including immunotherapies and targeted treatments, more than half of invasive melanoma patients ultimately succumb to the disease due to therapeutic resistance. To overcome this obstacle, strategies such as combining immunotherapies with targeted drugs or adding epigenetic therapies have been investigated. Tumor-infiltrating lymphocytes (TILs) therapy has emerged as a promising option for patients whose disease continues to progress despite standard treatments. This article aims to introduce TIL therapy and review recent outcomes in melanoma prognosis in its application for melanoma management.

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.

Tumor-infiltrating lymphocytes as a prognostic and predictive factor for Melanoma

INTRODUCTION

Tumor-infiltrating lymphocytes (TILs) have been investigated as prognostic factors in melanoma. Recent advancements in assessing the tumor microenvironment in the setting of more widespread use of immune checkpoint blockade have reignited interest in identifying predictive biomarkers. This review examines the function and significance of TILs in cutaneous melanoma, evaluating their potential as prognostic and predictive markers.

AREAS COVERED

A literature search was conducted on papers covering tumor infiltrating lymphocytes in cutaneous melanoma available online in PubMed and Web of Science from inception to 1 December 2023, supplemented by citation searching. This article encompasses the assessment of TILs, the role of TILs in the immune microenvironment, TILs as a prognostic factor, TILs as a predictive factor for immunotherapy response, and clinical applications of TILs in the treatment of cutaneous melanoma.

EXPERT OPINION

Tumor-infiltrating lymphocytes play a heterogeneous role in cutaneous melanoma. While they have historically been associated with improved survival, their status as independent prognostic or predictive factors remains uncertain. Novel methods of TIL assessment, such as determination of TIL subtypes and molecular signaling, demonstrate potential for predicting therapeutic response. Further, while their clinical utility in risk-stratification in melanoma treatment shows promise, a lack of consensus data hinders standardized application.

Regression in cutaneous melanoma: histological assessment, immune mechanisms and clinical implications

Tumour regression is an immunologically driven process that results in complete or partial disappearance of tumour cells. This can be observed in histological sections as replacement of tumour cells with fibrosis, angiogenesis, and a variable inflammatory infiltrate. In primary cutaneous melanoma, the prognostic significance of regression has been debated for decades, in part because inconsistent histological criteria are used in prognostication studies. It is broadly accepted that CD8+ T lymphocytes are the primary effectors of the anti-tumour response, but the interplay between melanoma and the immune system is complex, dynamic, and incompletely understood. Sustained progress in unravelling the pathogenesis of melanoma regression has led to the identification of therapeutic targets, culminating in the development of immune checkpoint inhibitors for the management of advanced disease. Modern techniques allow for high-resolution spatial analyses of the tumour microenvironment. Such studies may lead to better understanding of the immune drivers of melanoma regression, thereby facilitating the search for new prognostic and predictive biomarkers to assist clinical decision-making.

Addressing the importance of melanoma tumor-infiltrating lymphocytes in disease progression and clinicopathological characteristics

Tumor-infiltrating lymphocytes (TILs) in primary cutaneous melanoma are considered to represent the host's antitumor immunological response; however, whether there are associations between TIL grade and histopathological characteristics and disease survival remains controversial. BRAF mutational status has been established as a routine screening method in advanced malignant melanoma, and worse prognosis rates have been demonstrated in patients harboring BRAF mutations. However, the general impact of BRAF mutational status on survival and histopathological characteristics is still debated. The aim of the present study was to compare the value of the assessment of TIL grade in stages I-II nodular and superficial spreading melanoma and BRAF mutational status, and its influence on clinicopathological characteristics. Altogether, 85 patients at stage IA-IIC who underwent melanoma surgical treatment at the Riga East University Hospital between 2012 and 2017 were retrospectively enrolled in the study. The histopathological characteristics were assessed according to the current World Health Organization and The American Joint Committee on Cancer 8th edition guidelines. The current study showed that patients with melanoma with high TIL grade had significantly better progression-free survival than patients with low TIL grade (hazard ratio, 4.9; 95% CI, 2.3-11.2; P<0.0001). BRAF mutations were observed in 52 patients (61.2%). BRAF mutational status in melanoma was associated with Clark invasion level (P=0.045), patient age (P=0.02) and TIL (P=0.04). The assessment of TIL grade in stage I-II melanoma demonstrated prognostic significance value and may help improve risk assessment in the future.