Multiple primary malignancies involving lung cancer

Background: The incidence of multiple primary malignancies (MPM) has increased sharply in recent decades. However, the clinical characteristics and prognosis of MPM patients involving lung cancer were not fully elucidated. This retrospective study was designed to explore the clinical characteristics and prognosis of MPM patients involving lung cancer in the People's Republic of China. Methods: Of 5405 lung cancer cases diagnosed at the Guangdong Lung Cancer Institute between 2005 and 2013, we analyzed 185 patients (3.4 %) with MPM involving lung cancer. Results: Among 185 patients with MPM involving lung cancer, 10 (5.4 %) had three malignancies and 175 (94.6 %) had two malignancies. 10 patients with three malignancies were excluded from the analysis to avoid misunderstanding. Of 175 accompanying malignancies, 64 (36.6 %) were synchronous MPM patients and 111 (63.4 %) were metachronous MPM patients; 49 (28.0 %) were lung cancer first MPM patients and 126 (72.0 %) were other cancer first MPM patients. The most frequent accompanying malignancy was colon cancer (25/175), followed by rectal cancer (18/175), esophageal cancer (17/175), and thyroid cancer (13/175). Metachronous MPM patients showed significantly better overall survival (OS) than synchronous MPM, with a median OS of 72.8 (range 12.2-391.0) and 12.9 (range 0.8-86.3) months, respectively (P < 0.001). Cox regression analysis revealed that time of occurrence and stage were independent factors for OS. Conclusions: Colorectal cancer, esophageal cancer, and thyroid cancer were the tumors that most frequently accompanying lung cancer. Metachronous MPM patients showed significantly better OS compared with synchronous MPM patients.