Risk of Second Primary Lung Cancer Remains High in Smokers

Patients who are diagnosed with lung cancer but continue to smoke are at much higher risk of developing a secondary primary lung cancer (SPLC) compared with never smokers as well as those who have quit smoking, according to the largest analysis of its kind.

“This study, which looked at the relationship between smoking history and developing a second lung cancer, adds to the evidence of the harmfulness of cigarette smoking. We presumed that never smokers would have a lower risk than current smokers, but we were encouraged to find that quitting smoking lowered the risk of SPLC and quitters had similar overall survival rates as never smokers,” said John Michael Boyle, MD, lead author, a radiation oncology resident at Duke Cancer Institute in Durham, North Carolina.

“These findings confirm that smoking cessation is crucial and should be an integral part of patient care for all patients as well as cancer survivors.”

The study included 1484 patients who underwent surgery for stage I-IIIA non–small cell lung cancer between 1995 and 2008; this included 372 current smokers, 1014 former smokers, and 98 never smokers. The 5-year incidence of SPLC was 13%, 7%, and 0%, respectively, which was statistically significant when both current and former smokers were compared with never smokers (P = .03).

During follow-up, only 1 never smoker developed a second lung cancer 7 years later. The risk of SPLC increased with the number of years of tobacco exposure, equaling an 8% increased risk with every 10 pack-years.

The risk of developing SPLC was driven by cumulative smoking history, never smokers having zero risk at 5 years, and those who quit (whether <5 years ago or >5 years ago) having a similar 5-year risk of 7%; current smokers had a 12.8% risk.

Results for overall survival (OS) were quite different, Boyle explained. “OS was the worst for current smokers. Quitting smoking mitigated increased risk of mortality,” he noted. The rate of 5-year OS was 54.1% in never smokers, 46.1% in those who quit >5 years ago, 47.1% in those who quit <5 years ago, and 39% in current smokers.

No difference in rates of local control or distant metastasis was evident based on smoking status.

Reference

1. Boyle JM, Chino JP, Tandberg D, et al. Tobacco use and secondary lung malignancies after surgery for non-small cell lung cancer. Int J Radiat Oncol Biol Phys. 2014;90(1)(suppl):S79-S80. Presented at: 56th Annual Meeting of the American Society for Radiation Oncology; September 14-17, 2014; San Francisco, CA. Abstract 170.