OBJECTIVEThe aim of this study was to analyze the clinical characteristics and prognostic factors in patients with cancer of unknown primary site (CUP).

METHODSThe clinical and follow-up data of 68 CUP patients (46 adenocarcinoma patients, 22 squamous cell carcinoma patients), were retrospectively analyzed. Univariate and multivariate analysis were conducted to determine the correlation of survival with clinical features, tumor markers, blood test, liver function and so on.

RESULTSThe median survival time of the 68 CUP patients was 123 days. The results from univariate Cox regression analysis showed that the prognostic factors were related to a performance status, presence or absence of liver metastases, the number of metastatic sites, carcinoembryonic antigen (CEA), lactate dehydrogenase (LDH), hypoalbuminemia, hypohemoglobinemia and lymphocyte count. Multivariate Cox regression analysis of the clinical factors identified that a performance status (PS) ≥ 2, liver metastasis, elevated serum carcinoembryonic antigen (CEA) and lactate dehydrogenase (LDH) levels, hypoalbuminemia (< 35 g/L) and lymphopenia (≤ 0.7 × 10(9)/L) were significant independent unfavorable predictive factors. Based on the number of the unfavorable predictive factors, we divided all the patients into three subgroups: subgroup involving 0-1 unfavorable factor, subgroup involving 2 - 3 unfavorable factors and subgroup involving 4 - 6 unfavorable factors. The median survival time was 390 days, 138 days and 77 days, respectively, in the 3 subgroups. Compared with the other two groups, the survival of the subgroup involving 0 - 1 unfavorable factor was significantly longer (P < 0.05), the survival between the subgroup involving 2 - 3 unfavorable factors and subgroup involving 4 - 6 unfavorable factors was not significantly different (P > 0.05).

CONCLUSIONSA performance status ≥ 2, liver metastasis, elevated serum carcinoembryonic antigen and lactate dehydrogenase levels, hypoalbuminemia and lymphopenia are independent unfavorable prognostic factors in patients with cancer of unknown primary site. The patients who had more than 2 unfavorable prognostic factors have a worse prognosis.