OBJECTIVETo explore the prognostic factors and their impact on survival of patients with cancer of unknown primary (CUP).

METHODSThe clinical and follow up data of 154 CUP patients referred to the Cancer Hospital & Institute, Chinese Academy of Medical Sciences from January 1, 2003 to December 31, 2007 were analyzed. Multivariate analysis of survival was performed using recursive partitioning referred to as classification and regression tree (CART) analysis.

RESULTSThe median survival for 154 eligible consecutive CUP patients was 18.2 months, and the 5-year survival rate was 1.3%. CART was performed with an initial split on age of 34, and 5 terminal subgroups were formed. The median survival of the 5 subsets ranged from 5.5 months (younger than 34 years old subgroup) to 61.8 months for patients at age of 34 to 60, with one or two organ sites involved, and non-adenocarcinoma histology subsets.

CONCLUSIONSCART can be used to identify previously unappreciated patient subsets and is a useful method for dissecting complex clinical situations and identifying homogeneous patient populations in clinical practice and future clinical trials.