NEW YORK (Reuters Health) - Family history and environmental arsenic contamination appear to be independent risk factors for lung cancer, according to reports in the Journal of the American Medical Association for December 22/29.
However, tobacco smoke remains the leading cause of lung cancer, and seems to have synergistic effects with other risk factors, the researchers note.
Other large, registry-based studies have suggested that genetic predisposition plays a role in lung cancer incidence, explain Dr. Kari Stefansson, at deCODE Genetics, and colleagues in Reykjavik, Iceland. However, those studies did not control for smoking, leaving open the possibility that the increased risk among family members may be due to shared environment or familiality of nicotine addiction and smoking.
Dr. Stefansson’s group therefore identified records from the Icelandic Cancer Registry of 2756 patients diagnosed with lung cancer between 1955 and 2002, linking them with a nationwide genealogical database of all living Icelanders and including data regarding smoking history from the Reykjavik Heart Study.
Parents, siblings and offspring of lung cancer patients exhibited risk ratios (RR) of 1.96 to 2.69 (p < 0.001). Results were even more pronounced when limiting the analysis to individuals age 60 years or younger at disease onset, RR 2.84 to 3.48 (p = 0.007 to < 0.001).
The risk was also significantly elevated for second-degree and third-degree relatives.
Comparing RRs for lung carcinoma versus RRs for smoking, they found that the risk for lung cancer was significantly higher than that for smoking, “demonstrating that increased risk for relatives of patients with lung carcinoma is not solely due to smoking,” they write.
In the second report, Dr. Chien-Jen Chen, at National Taiwan University in Taipei, examined lung cancer rates among 10,591 residents in two areas of Taiwan with arsenic-contaminated wells. Residential history and duration of drinking well water were used to estimate cumulative arsenic exposure, while cancer incidence was estimated through linkage with a national cancer registry.
During follow-up of 8 years, there were 139 incident cases of lung cancer.
For those with the highest arsenic level (at least 700 microgram/liter) and after adjusting for demographics and cigarette smoking status at recruitment, the relative risk for lung cancer was 3.29.
After adjusting for ingested arsenic exposure and other risk factors, a history of smoking was associated with a 4-fold increased risk.
Compared with non-smokers at the lowest level of arsenic exposure, those with the highest exposure to both factors had more than 11-fold increased risk. Approximately one third to one half of cases could be attributed to the combined effect of the two risk factors.
In a related editorial, Dr. Habibul Ahsan, at Columbia University in New York, and Dr. Duncan C. Thomas at the University of Southern California, Los Angeles, comment that, regardless of the “roles of familial aggregation and environmental exposures to arsenic or other carcinogens, lung cancer is primarily caused by tobacco smoking -- an exposure that is largely preventable.”
Source: JAMA 2004;292:2977-2990,3026-3029. [ Google search on this article ]
MeSH Headings:Lung Neoplasms: Neoplasms: Neoplasms by Site: Respiratory Tract Neoplasms: Smoking: Thoracic Neoplasms: Arsenic Poisoning: DiseasesCopyright © 2002 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.
