- Second primary lung cancer rates are higher in patients with prior breast cancer (BC), with the risk greatest in those with triple-negative BC (TNBC).
Why this matters
- The extent to which a history of BC increases lung cancer risk was unclear.
- 620,429 women from the Surveillance, Epidemiology, and End Results database diagnosed with BC between 2000 and 2014.
- Funding: National Natural Science Foundation of China; others.
- 6269 cases of second primary lung cancers; 87.3% NSCLC, 12.7% SCLC.
- Slightly higher rates of second primary lung cancer in patients with BC vs the general female population (standardized incidence ratio [SIR], 1.03; 95% CI, 1.00-1.06).
- Lung cancer risk was highest within 1 year of BC diagnosis (SIR, 1.31; 95% CI, 1.23-1.39) and with BC diagnosis at age 20-39 years (SIR, 2.40; 95% CI, 1.75-3.23).
- Patients with TNBC had highest lung cancer risk of all subtypes (SIR, 1.59; 95% CI, 1.29-1.94).
- 63.4% of patient deaths were attributed to lung cancer, with SCLC conveying the highest mortality (72.3%).
- OS was worse in patients with NSCLC who were negative for estrogen and progesterone receptors, whereas BC characteristics did not influence OS in patients with SCLC.
- Retrospective study with no data on treatment.