Abstract
BACKGROUND: Liver metastases from cancer of unknown primary (CUPL) constitute a rare disease, particularly among individuals younger than 50 years old. This paper aims to investigate the clinical characteristics of patients with CUPL and analyze prognostic differences across distinct age groups. METHODS: Data pertaining to patients with CUPL were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Propensity score matching (PSM) was employed to adjust for clinical variables. Cox regression analysis identified risk factors influencing overall survival (OS), while competing-risk analyses were conducted to determine prognostic factors for cancer-specific survival (CSS). Survival differences were compared using the Kaplan-Meier method and cumulative incidence function (CIF). RESULTS: The study encompassed 4,691 patients, with 319 (6.8%) in the age <50 years group and 4,372 (93.2%) in the age ≥50 years group. Individuals with unexplained liver metastases exhibited a 1-year OS rate of 14.7% and a 1-year CSS rate of 23%. Following matching, age, histology, brain metastases, and chemotherapy were identified as independent prognostic factors affecting OS. Additionally, race, grade, histology, brain metastases, and chemotherapy were recognized as independent prognostic factors influencing CSS. Notably, the age <50 years group demonstrated superior OS and CSS compared to the age ≥50 years group before and after PSM. Among patients undergoing chemotherapy, the age <50 years group exhibited enhanced OS and CSS compared to their age ≥50 years counterparts. Furthermore, in individuals subjected to radiotherapy, the age <50 years group demonstrated superior OS, although no significant difference in CSS was observed. CONCLUSIONS: The survival prognosis of patients with CUPL was found to be poor. However, both OS and CSS were more favorable in the age <50 years group compared to the age ≥50 years group. Additionally, radiotherapy and chemotherapy were associated with an OS benefit for patients in the age <50 years group.