Incidence of Smoking-Related Second Primary Cancers After Lung Cancer in Germany: An Analysis of Nationwide Cancer Registry Data

Introduction: Approximately 80% of lung cancer cases in Germany are attributable to smoking. Patients with a lung cancer diagnosis may remain at increased risk of developing smoking-related second primary cancers (SPCs). Methods: Anonymous data from 11 population-based cancer registries covering approximately 50% of the German population were pooled for the analysis. Included patients were diagnosed with having an index lung cancer between 2002 and 2013, aged 30 to 99 years old at diagnosis, and survived for at least 6 months. We calculated standardized incidence ratios (SIRs)—stratified by age, sex, region, and period—comparing the incidence of smoking-related and other SPCs to the general population. Results: Of the 135,589 lung cancer survivors (68.2% male; mean follow-up 30.8 mo) analyzed, 5298 developed an SPC. In males, the risk was particularly high for SPCs of the larynx (SIR = 3.70, 95% confidence interval [CI]: 3.14–4.34), pharynx (3.17, 2.61–3.81), and oral cavity (2.86, 2.38–3.41). For females, SIRs were notably elevated for the esophagus (4.66, 3.15–6.66), oral cavity (3.14, 2.03–4.63), and urinary tract (2.68, 2.04–3.45). When combining all smoking-related cancer sites, SIR was 1.41 in males (95% CI: 1.36–1.47) and 1.81 in females (95% CI: 1.68–1.94). We observed that males had a 1.46-fold (95% CI: 1.37–1.56) and females a 1.33-fold (95% CI: 1.20–1.47) increased risk for smoking-related compared with other cancers. Conclusions: Patients with primary lung cancer were at increased risk for developing a smoking-related SPC. Therefore, the advantages of increased patient surveillance and the benefits of smoking cessation strategies should be considered.