Incidence of Second Malignancy after Successful Treatment of Limited-Stage Small-Cell Lung Cancer and Its Effects on Survival.

INTRODUCTION: Extended survival outcomes from improved treatments for patients with cancer come with an increased risk for development of a metachronous second malignancy (MSM). We evaluated the incidence of MSM after successful treatment of SCLC and compared survival between patients with SCLC in whom MSM developed and those in whom it did not. METHODS: Selection criteria were a diagnosis of limited-stage SCLC and receipt of at least 45 Gy of radiotherapy and chemotherapy at a single institution in 1985-2012. MSM was defined as a tumor of a different histologic type than the primary that appeared more than 2 years after the diagnosis of SCLC. RESULTS: Of 704 patients identified, 32 were excluded for lack of follow-up, 48 for having SCLC as MSM after treatment of another type of cancer, 37 for nonmelanoma skin cancer as MSM, and 46 for MSM within 2 years after SCLC diagnosis. Of the remaining 541 patients, 346 had recurrent SCLC, 180 had no second malignancy and no recurrence, and 15 (2.8%) had MSM (13 in a lung [eight adenocarcinomas and five squamous cell carcinomas], one sarcoma, and one acute myeloid leukemia). All 15 patients with MSM achieved complete response to the SCLC treatment. Overall survival was longer for patients with MSM than for patients with no other malignancies and no recurrence, with 10-year rates of 61.9% (95% confidence interval: 30.0%-82.6%) and 29.9% (95% confidence interval: 21.5%-38.6%), respectively (p = 0.03). CONCLUSIONS: Long-term survivors after treatment for SCLC should be made aware of the risk for MSM and the necessity of follow-up.