Multiple primary malignancies in patients with non-small cell lung cancer

Objective Information regarding multiple primary malignancies is important, as it has the potential to clarify etiological factors and may indicate the need to refine patient follow-up to include screening for associated malignancies. Upper aerodigestive tract cancer often develops in patients with smoking-related lung cancer; however, little is known about the frequencies or types of other primary malignancies in patients with non-small cell lung cancer (NSCLC) without a history of smoking. Methods We retrospectively evaluated the records of patients examined and/or treated for NSCLC at the Institute of Biomedical Research and Innovation between January 2007 and June 2012. Patients In total, 938 patients, including 599 men (never-smoker/ever-smoker: 35/564) and 339 women (never-smoker/ever-smoker: 236/103), were analyzed. Results Among the 209 patients (22.3%) with multiple primary malignancies, 151 had a history of smoking and 58 were never-smokers. The most common cancers were gastric (43 cases), colorectal (33 cases), and prostate (29 cases) cancer. Smoking-related cancer was more common in current smokers and ex-smokers for both men and women. Among women with NSCLC, never-smokers were more likely to have thyroid cancer than those with a history of smoking (5.1% vs. 0%, p=0.021). Conclusion In this study, several differences in malignancies were observed between never-smokers and patients with a history of smoking. Thyroid cancer and NSCLC co-existed in some women without a history of smoking, implicating predisposing factors other than tobacco smoke in the onset of these cancers.