Based on recent development in the treatment of small-cell lung cancer (SCLC) such as chemotherapy and radiotherapy, long-term survivors are frequently observed. Meanwhile, etoposide and radiotherapy, which are key treatments for SCLC, are also known as methods to set up late complication including carcinogenicity. There have been few reports of second primary malignancies (SPM) in patients with SCLC, and risk factor for SPM has not become evident other than smoking continuation.Methods
From July 1992 to December 2009, 900 patients with SCLC were treated in National Cancer Center Hospital East. Medical records of all patients were retrospectively reviewed, and the incidence and risk factor for SPM were investigated.Results
Demographics of all patients with SCLC were as follows: male/female, 738/162; median age, 66 years (range 22–87); smoking pack-year (PY) <30/30 = < 155/745; limited/extensive, 468/432. Median follow-up time was 4.5 years. Three and 5-year overall survival rates were 16.4% and 11.6%, respectively. Twenty-seven patients (3.0%) developed SPM, 15 patients (54%) of whom died due to SPM. Thoracic cancer occupied 52% of them (lung, 11; trachea, 1; esophagus, 4; breast, 1). Three and 5-year cumulative incidence rates (CIR) of SPM were 2.5% and 11.8%, respectively. Although there was no significant risk factor for SPM, the groups having past history of malignant disease and heavy smoker (PY; ≥30) tended to develop SPM (P = 0.11and 0.07). Using etoposide containing regimen and thoracic irradiation were not significant risk factors for the incidence of SPM (P = 0.84 and 0.24). Neither serum level of CEA, NSE nor ProGRP were risk factors of incidence of SPM (P = 0.51, 0.09 and 0.21). Within over 2-year survivors, there was a significant correlation between family history of cancer within first-degree relatives and CIR of SPM (P < 0.01).Conclusions
Five-year CIR of SPM was 11.6%, and secondary thoracic cancer accounted for a large portion of them. It was concluded that cumulative smoking amount, past history of malignant disease, and positive family history of cancer within first-degree relatives were risk factors for SPM.