Clinical characteristics and prognostic significance of 92 cases of patients with primary mixed-histology lung cancer

Mixed-histology primary lung cancer is a rare type of lung cancer, where data regarding epidemiology, clinical features and prognosis of survival are limited. The aim of this study was to analyze the clinical characteristics of patients with mixed-histology lung tumors, and to investigate the association between clinical characteristics, treatment and prognosis. Between January, 1999 and September, 2008, 1,842 patients were diagnosed with primary lung tumors. Of these, 92 presented a mixed histological pattern. Patient clinical characteristics, clinical tumor-node-metastasis (TNM) staging, diagnostic methods, treatment and survival data were collected in order to be retrospectively analyzed. Differences between the frequencies were examined using the χ(2) test and survival rates using the Kaplan-Meier method. The log-rank test was used to compare the survival curves and a probability value <5% (P<0.05) was considered to indicate a statistically significant difference. Of the 92 lung cancer patients (4.99%) with a mixed histological pattern, most were adenosquamous carcinomas. Patients included 75 men and 17 women with a mean age of 56 years. Most cases were in late stage and 64 patients had metastasis. The 1-, 2- and 3-year survival of 52 mixed-histology and 54 non-small cell lung cancer (NSCLC) patients with resection who were successfully followed up, was 63.5, 23.1, 9.6 and 81.5, 48.1, 27.7% (P=0.013). The median survival time of mixed-histology lung cancer patients treated with surgery plus adjuvant therapy and surgery alone was 22 and 12 months, respectively (P=0.002). Mixed-histology lung cancer is characterized by higher malignancy and poor prognosis. However, surgery plus adjuvant therapy is able to prolong survival, compared to surgery alone.