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.

e20649 Background: Thymic epithelial tumors (TETs) are a rare, heterogeneous group of malignancies that arise from the thymus. While the etiology of TETs remains unknown, variation in incidence rates amongst racial/ethnic groups has raised the possibility of germline predispositions. Unfortunately, due to the rarity of this disease, there is a limited understanding of the impact of race/ethnicity on tumor characteristics and treatment outcomes for TET patients. We sought to characterize patient/tumor data and investigate treatment outcomes based on race and ethnicity. Methods: We conducted a single-institution, retrospective database analysis of TET patients evaluated at the IUSCCC from 1979 – 2021 from which clinical annotations were available for 477 thymoma and 164 thymic carcinoma (TC) patients. We identified 112 thymoma and 35 TC patients who were deemed to have sufficient data for evaluation of racial/ethnic characteristics. Demographic/clinical variables and therapeutic interventions, including treatment outcomes, were analyzed. Data was compiled and analyzed using descriptive statistics and the Kaplan Meier method for survival analysis via GraphPad Prism software. Results: Of the 112 thymoma patients, 29 thymoma patients presented with de novo metastatic disease at the time of diagnosis. The median age at the time of diagnosis of all patients revealed a statistically significant difference between White and Black TET patients (53.0 v. 42.0 years, *p = 0.0195). There was a trend towards significance when median age of diagnosis between White and Asian TET patients was compared (53.0 v. 48.0 years, p = 0.0633, NS). Advanced histologic subtypes, include B3 and TC, appeared predominantly in Asian and Black patients at 77.7% and 56.3%, respectively, compared to White patients (44.9%), though the finding was not statistically significant. No statistically significant differences between racial/ethnic groups regarding progression free survival for unresectable or metastatic disease were observed, regardless of histology. There was a non-significant difference in recurrence free survival for resectable thymoma in White (30.0 months) and Asian/Pacific Islander (47.0 months) patients compared to Black patients (24.0 months). Conclusions: Overall, this analysis suggests differences in the median age of diagnosis for patients with thymic malignancies based on race, raising the possibility of inherent biologic differences driving oncogenesis and symptoms at the time of presentation. While no statistically significant differences in treatment outcomes were found based on race and ethnicity, Black patients appeared to experience shorter times to recurrence after definitive surgery. Further studies to understand the mechanistic differences driving tumorigenesis and potential disparities in treatment outcomes are greatly needed in this rare tumor type.

Background and Hypothesis:Thymic Epithelial Tumors are uncommon tumors of the anterior mediastinum composed ofthymomas and thymic carcinomas (TC). TC’s are known to have worse disease outcomes andlower rates of survival in comparison to thymomas and are suspected to have lower responserates to chemotherapy as well. As these tumors are rare, little data exists assessing the trueefficacy of chemotherapeutic regimens for TC patients. Due to this lack of data, and that theIndiana University Health Simon Cancer Center treats a high percentage of TET patients, adatabase of these patients covering a variety different disease characteristics and treatmentshas been established. We hypothesize, upon evaluation of this database, response rates toanthracycline based regimens (PAC) will be superior to non-anthracycline based regimens (i.e.,PE, Carbo/Taxol) for TC patients. Methods:In this project, a collection of patients seen by Dr. Patrick Loehrer and/or Dr. Kenneth Keslerwas acquired, and a database was created using these patients in RedCap. Once established,we evaluated patient medical records in Cerner and entered data related to diseasecharacteristics and treatments. These patients were then analyzed accordingly to evaluatechemotherapy response rates. Results:The database yielded 123 instances of chemotherapy treatment for TC. Of which, the mostpopular treatments were PAC and Carbo/Taxol. The data suggests that PAC generates a higherresponse rate (65.5%) than other therapies (Carbo/Taxol: 27.6%, PE: 58.3%, etc.). Therefore,there is evidence that anthracycline based regimens may be more effective at generatingresponse rates in comparison to non-anthracycline based regimens. Conclusion and Potential Impact:This project will help elucidate the effectiveness of recommended systemic therapies for thymiccarcinoma patients from one of the largest TET databases constructed. Ultimately, we hope thatwith clarity of the effectiveness of treatment, this can serve as a reliable reference for evidencebasedmedicine for the care of TC patients.