Significance of Smoking in Second Primary Lung Cancer Incidence

After an initial primary lung cancer diagnosis (IPLC), the incidence of second primary lung cancer (SPLC) is as high among never-smokers as it is among ever-smokers, according to a recent population-based, prospective, cohort study.

The researchers analyzed data from the Multiethnic Cohort Study, which included more than 211,000 participants who were enrolled between April 18, 1993, and December 31, 1996. The follow-up period was through July 1, 2017.

The study population was 16.2% Black, 26.4% Japanese American, 22.1% Latino, 6.7% Native Hawaiian, 23.0% White, and 5.7% other.

At baseline, risk factors, including smoking, alcohol consumption, and physical activity, were self-reported through a questionnaire. Participants were aged 45 to 75 years.

The current study, conducted by Eunji Choi, PhD, and colleagues, had two primary outcomes: 10-year cumulative incidence of IPLC and SPLC and standardized incidence ratio (SIR) by smoking history.

Among participants, 7161 (3.96%) developed IPLC over 4,038,007 person-years and 163 (2.28%) developed SPLC over 16,470 person-years. Moreover, the 10-year cumulative IPLC incidence (2.4%) in individuals who had smoked was seven times higher than those who never did.

In addition, the 10-year cumulative SPLC incidence following IPLC was as high among never-smokers (2.84%) as ever-smokers (2.72%). The SIR in never-smokers was significantly higher than in individuals who had never smoked (14.5 vs 3.5, respectively).

The study findings suggest there is a need to identify risk factors for SPLC among patients who never smoked and to develop a targeted surveillance strategy, according to the researchers.