Prognostic factors among patients with brain metastases from cancer of unknown primary site

Purpose Cancers of an unknown primary site (CUPs) have a dismal prognosis, and the situation is even worse for CUPs patients with brain metastases (BM-CUPs). This study aims to give better insight into the occurrence and survival of BM-CUPs patients. Methods Cases were selected from the Netherlands Cancer Registry (1,430 BM-CUPs/17,140 CUPs). Baseline characteristics between CUPs patients with and without BM were tested using chi-square tests and Mann–Whitney U tests. Patients’ overall survival (OS) times were estimated by the Kaplan–Meier method and prognostic factors on OS was assessed using Cox proportional hazards regression analyses. Results The proportion of BM-CUPs patients among CUPs increased from 8% in 2009–2010 to 10% in 2017–2018 ( p