An evaluation of cisplatin, doxorubicin, and cyclophosphamide (PAC) compared to other regimens for patients with unresectable or metastatic thymic carcinoma: A single-institution retrospective analysis.

Abstract

e20650 Background: Thymic Epithelial Tumors (TETs) are uncommon tumors of the anterior mediastinum comprised of thymomas and Thymic Carcinomas (TC). Given the rarity of these tumors, little data exists regarding the comparative effectiveness of various combination therapies. Platinum-based treatment regimens in combination with anthracyclines (e.g., PAC), taxanes (e.g., carboplatin plus paclitaxel (CT)) or etoposide (PE) have demonstrated efficacy in TETs in the front-line setting (although current NCCN guidelines recommend only CT for the treatment previously untreated advanced TC). We sought to characterize the efficacy of these regimens for TCs in a real-world setting. Methods: We conducted a single-institution, retrospective database analysis of 164 TC patients seen at the IUSCCC from 1996 - 2020. Of those patients, 42 met the study criteria as having a de novo diagnosis of TC treated with front-line systemic chemotherapy and available outcome data. Chemotherapeutic intervention and demographic/clinical variables were evaluated in this study. Data was compiled and collected using descriptive statistics and the Kaplan Meier method for survival analysis via GraphPad Prism software. Results: Of the 42 patients identified to have sufficient data, the median age was 55.6 years (range, 21 - 82). The median follow-up for patients was 23 months. Metastatic sites of disease included the pleura (11%), lymph nodes (11%), bone (10%) and lungs (5%). Multi-site involvement accounted for 36% of cases. Squamous cell carcinoma (SCC) was found in 52.3% (n = 22) of the patients, while 26.2% (n = 11) had rare TC subtypes, including, SCC with basaloid features, SCC with neuroendocrine features, and neuroendocrine (21.4% of cases were classified as TC only). Most patients received first line treatment with PAC (n = 16), CT (n = 13) or PE (n = 9). There was no difference in progression free survival (PFS) for TC patients treated with PAC or CT (10.5 v. 7.5 months, respectively, NS). PE was associated with inferior outcomes compared to PAC (4.5 vs. 10.5 months, ***p = 0.0005) and CT (4.5 vs. 7.5 months, *p = 0.0158), respectively. A subgroup analysis of rarer histologic subtypes revealed a trend towards improved PFS for patients who received PAC compared to CT (9.5 v. 4.5 months, NS). Conclusions: The results of our study support PAC combination chemotherapy as a reasonable alternative for patients with previously untreated advanced TC. Further studies to correlate the genomic differences of common and uncommon TC subtypes will be crucial to optimize the role of conventional and targeted systemic therapies in this rare malignancy.