SMOKING CESSATION AFTER SUCCESSFUL TREATMENT OF SMALL-CELL LUNG-CANCER IS ASSOCIATED WITH FEWER SMOKING-RELATED 2ND PRIMARY CANCERS

Objective: To determine the incidence of second primary cancers developing in patients surviving free of cancer for 2 or more years after treatment for small-cell lung cancer and to assess the potential effect of smoking cessation. Design: Retrospective review of 540 patients from a single institution with a median follow-up of 6.1 years. Setting. A single government institution (the National Cancer Institute). Patients: Consecutive sample of 540 patients with histologically confirmed small-cell lung cancer treated from 1973 through 1989 on therapeutic clinical trials. Measurements: The relative risk for second primary cancers and death were calculated in patients who remained free of cancer for 2 years after initiation of therapy. The relation of these end points to smoking history was also determined. Results: Fifty-five patients (10%) were free of cancer 2 years after initiation of therapy. Eighteen of these patients developed one or more second primary cancers, including 13 who developed second primary non-small-cell lung cancer. The risk for any second primary cancer compared with that in the general population was increased four times (relative risk, 4.4; 95% CI, 2.5-7.2), with a relative risk of a second primary non-small-cell lung cancer of 16 (CI, 8.4-27). Forty-three patients discontinued smoking within 6 months of starting treatment for small-cell lung cancer, and 12 continued to smoke. In those who stopped smoking at time of diagnosis, the relative risk of a second lung cancer was 11 (CI, 4.4 to 23), whereas, in those who continued to smoke, it was 32 (CI, 12 to 69). Conclusions: Patients with small-cell lung cancer who survive cancer-free for more than 2 years have a significantly increased risk for development of a second primary smoking-related cancer. Cigarette smoking cessation after successful therapy is associated with a decrease in risk for a second smoking-related primary cancer.