Clinical characteristics and prognosis of lung metastases from unknown primary cancer sites

Objectives Limited knowledge exists regarding lung metastases from cancer of unknown primary (CUPL), particularly concerning young patients. This study aims to investigate the clinicopathologic features and prognostic factors of CUPL patients, with a specific focus on comparing the survival outcomes across different age groups. Methods We conducted a retrospective analysis of patients diagnosed with CUPL between 2010 and 2020, utilizing the SEER database. Clinical characteristics among different age groups were compared. Prognostic factors influencing overall survival (OS) in CUPL patients were assessed through Cox regression analysis, while competing risks analysis was employed to evaluate cancer-specific survival (CSS) prognostic factors. A comparison of survival differences between age groups was conducted utilizing the Kaplan-Meier and Cumulative Incidences Function. Results A total of 2,474 patients with CUPL were included in this study, predominantly in the middle-aged and elderly demographic. The median survival time was a mere 1 month, with a one-year OS rate of 11 % and a one-year CSS rate of 13.8 %. Age, tumor histological typing and grading, liver metastasis, bone metastasis, radiotherapy, and chemotherapy were identified as independent prognostic factors affecting both OS and CSS. Despite the small representation of young patients (<40 years old) at 3 %, their OS and CSS rates significantly surpassed those of middle-aged (40-70 years old) and elderly patients (>70 years old). This advantage persists among patients undergoing radiation and chemotherapy. Conclusions While exceedingly uncommon among young patients, the prognosis for survival is more favorable than in middle-aged and elderly patients. Administration of radiotherapy and chemotherapy emerges as a potential avenue to enhance the survival prognosis for CUPL patients.