Efficacy and safety of treatments for advanced thymic carcinoma after failure of first-line platinum-based chemotherapy: A systematic literature review and meta-analysis

Thymic carcinoma (TC) is a rare cancer and patients failing initial chemotherapy (relapse/refractory) face limited therapeutic options given no approved options or consensus standard of care. This study aimed to identify and summarize clinical outcomes of all regimens evaluated in clinical trials of relapsed or refractory patients. Interventional trials enrolling advanced TC patients who failed first-line chemotherapy and reported outcomes in this group were eligible for inclusion in our systemic literature review (SLR). Between-study heterogeneity was assessed to determine the feasibility of pooling specific studies and treatments. Objective response rate (ORR), overall survival (OS), progression-free survival (PFS), and duration of response (DOR) endpoints were of interest for meta-analysis. Nineteen trials were identified in the SLR. Three trials with one or two TC patients were removed from our assessment to reduce publication bias. Response rates among studies with at least ten TC patients varied from 9 % to 38 %. Pooled ORRs in patients receiving S-1 (46 patients), sunitinib (46 patients), or pembrolizumab (66 patients) were 28 %, 24 %, and 21 %, respectively. Prolonged duration of response with pembrolizumab was observed with a pooled median of 23.8 months (95 % confidence interval [CI]: 12, not reached). Median PFS of five months or greater was reported in patients treated with sunitinib, lenvatinib, pembrolizumab, capecitabine + gemcitabine, everolimus, or S-1. Median OS of 20 months or greater was reported in trials evaluating S-1 or pembrolizumab; this endpoint was not reached in trials evaluating lenvatinib, regorafenib, or sunitinib. Generalizability of treatment effects is challenging in the research of rare diseases and meta-analysis of clinical outcomes may help to increase precision and relevance of results to the larger TC population. Our study found limited treatment options upon relapse, demonstrating a need for further investigations into novel therapeutics and well-powered clinical trials to better inform on optimal treatments.

Differential activity of avapritinib in patients with metastases from mucosal melanoma and thymic carcinoma harbouring KIT exon 17 mutations: Initial experience from a Compassionate Use Program in Italy

INTRODUCTION

Proto-oncogene KIT is the gene encoding the receptor tyrosine kinase protein KIT. Activating mutations are found in 2.9% of neoplasms, with the highest prevalence in gastrointestinal stromal tumour. Exon 17 mutations typically alter the kinase activation loop and are relatively rare, representing 11.7% of all activating KIT mutations. Recently, KIT exon 17 mutants turned out to be a potential molecular target for the type 1 kinase inhibitor avapritinib (BLU-285).

OBJECTIVE

In this framework, we aimed at investigating the potential activity of avapritinib in mucosal melanoma and thymic carcinoma, two disease histologies with dismal prognosis, currently lacking evidence-based second line treatment options and in which KIT exon 17 activating mutations could represent a relevant therapeutic target.

RESULTS

In this series, we report the only four cases of patients affected by exon 17 mutant mucosal melanoma and thymic carcinoma that have been treated in Italy with avapritinib within a Compassionate Use Program. Two patients harboured mucosal melanoma and the other two were diagnosed with thymic carcinoma. We describe a differential activity of avapritinib (3/4 patients responded, 1/4 did not respond), along with possible hypotheses to justify such differences and potential implications for precision oncology.

CONCLUSIONS

Taken together, the inactivity of imatinib on KIT exon 17 mutations, the general low clinical efficacy of immunotherapy, as well as the consequent formal lack of standard available and active second line systemic treatments in both mucosal melanoma and thymic carcinoma, support the implementation of avapritinib in the therapeutic armamentarium, even though further prospective evidence is warranted.

Immunobiology of Thymic Epithelial Tumors: Implications for Immunotherapy with Immune Checkpoint Inhibitors

Thymic epithelial tumors (TETs) are a group of rare thoracic malignancies, including thymic carcinomas (TC) and thymomas (Tm). Autoimmune paraneoplastic diseases are often observed in TETs, especially Tms. To date, chemotherapy is still the standard treatment for advanced disease. Unfortunately, few therapeutic options are available for relapsed/refractory TETs. In the last few years, the deepening of knowledge on thymus' immunobiology and involved altered genetic pathways have laid the foundation for new treatment options in these rare neoplasms. Recently, the immunotherapy revolution has landed in TETs, showing both a dark and light side. Indeed, despite the survival benefit, the occurrence of severe autoimmune treatment-related adverse events has risen crescent uncertainty about the feasibility of immunotherapy in these patients, prone to autoimmunity for their cancer biology. In this review, after summarizing immunobiology and immunopathology of TETs, we discuss available data on immune-checkpoint inhibitors and future perspectives of this therapeutic strategy.