Survival in patients with cancer of unknown primary site (CUP): Mayo Clinic experience

e18802 Background: CUP is a rare cancer with an incidence of 7–12 cases per 100,000/year. CUP is defined as metastatic cancer with no identifiable primary tumor despite comprehensive evaluation. Despite its heterogeneous clinicopathological presentation, the treatment of CUP has primarily been with platinum-based combination chemotherapies but results are poor and survival is short. Here, we describe survival outcomes in real-world dataset of patients with CUP seen at a tertiary referral center. Methods: Retrospective study of patients treated at Mayo Clinic, Rochester MN, from 2010 to 2021. Survival probabilities were estimated with the Kaplan-Meier method. We used Cox proportional hazard regression with forward modeling to explore the association between each variable and death. Overall survival (OS) analysis was conducted in the entire cohort, and it was stratified by histological subtype. For the hypothesis test, we considered p < 0.05 to be statistically significant; all tests were two-sided. All data were analyzed by the SPSS version 22.0 software (SPSS, Chicago, IL, United States). Results: From a total of 214 patients, 198 patients were included in the survival analysis. The patients were predominantly white (87%), female (50.2%), with a mean age of 63 (SD: 13) without history of smoking (51%). The predominant histology was adenocarcinoma (30%), followed by neuroendocrine neoplasms (NEN) (27%), carcinoma NOS (25%), squamous cell carcinoma (SCC) (10%) and non-classifiable tumors (7%). The median follow-up time was 23 months, and medial OS was 23 months in the entire cohort. OS by histology was as follows: 51 months for NEN, 34 months for SCC, 18 months for carcinomas NOS and 11 months for adenocarcinomas (p < 0.001) (fig.1). Similar OS trends were observed when we restricted the analysis to poorly differentiated tumors. The 3- and 5-year cumulative survival by histology were as follows: 7% and 0% for adenocarcinoma, 25% and 8% for carcinoma NOS, 39% and 17% for SCC, and 56% and 22% for NEN. In Cox regression models we did not identify any prognostic factors among patients with adenocarcinoma. Conclusions: Patients with adenocarcinoma of unknown primary possess a considerable challenge and the OS is short. CUP of other histologies have higher OS. This study highlights the need of accurate tumor identification and better treatment, perhaps as a multiomics therapeutic approach.