Clinical features and outcomes of patients with stage I multiple primary lung cancers.

The number of patients with multiple primary lung cancers (MPLC) is rising. We studied the clinical features and factors related to outcomes of MPLC patients, using the database of surgically resected lung cancer (LC) cases compiled by the Japanese Joint Committee of Lung Cancer Registry. From the 18,978 registered cases, 9,689 patients with clinical stage I non-small cell lung cancer who achieved complete resection were extracted. Tumors were defined as synchronous MPLC when multiple LC was simultaneously resected or treatment was performed within 2 years after the initial surgery, while metachronous MPLC was defined as second LC treated more than 2 years after the initial surgery. Of these cases, 579 (6.0%) were synchronous MPLC and 477 (5.0%) metachronous MPLC, with 51 overlapping cases. Whereas female, non-smoker, low consolidation tumor ratio (CTR), and adenocarcinoma were significantly more frequent in the synchronous MPLC group, patients with metachronous MPLC had higher frequencies of males, smokers, chronic obstructive pulmonary disease (COPD), and non-adenocarcinoma. There was no significant difference for survival rate between patients with and without synchronous or metachronous MPLC. Age, gender, CTR for second LC, and histological combination of primary and second LC were prognostic indicators for both types of MPLC, while logistic regression analysis showed that female, history of malignant disease other than LC, and COPD were risk factors for MPLC incidence. The present findings may have major implications regarding MPLC diagnosis and identification of independent prognosticators, and provide valuable information for postoperative management of patients with MPLC.