ATS: Lung Cancer Isn't Stymied by Daily Dose of Vitamins

SAN FRANCISCO, May 23 -- Vitamin supplements do not protect against lung cancer and vitamin E may even elevate risk slightly for some patients, according to researchers. Multivitamins, vitamin C, and folate did not decrease lung cancer risk even at high intake levels; vitamin E increased relative risk 7% for each 100 mg/day increase over 10 years in a cohort study, found Chris Slatore, M.D., of the University of Washington in Seattle, and colleagues.
"We've known for a long time that fruits and vegetables protect against lung cancer," he said at the American Thoracic Society meeting here. "It's hard to get people to change their diet. The hope was that it would be easier to get them to take a pill."
One study stemming from this hope was the large Beta-Carotene and Retinol Efficacy Trial (CARET). When it found beta-carotene and retinol supplements increased lung cancer risk, particularly among smokers, researchers started looking more closely at the relationship, Dr. Slatore said.
So, he and his colleagues undertook the VITamins And Lifestyle (VITAL) study to look at supplements and various types of cancer, including prostate, breast cancer, and lung cancer.
Dr. Slatore and colleagues analyzed lung cancer specific outcomes for this cohort of 77,721 men and women aged 50 to 76 living in Washington state.
Participants completed a 24-page questionnaire on type, dose, and duration of vitamin supplement use over the prior 10 years. They were monitored for incident lung cancer over about four years using the Seattle-Puget Sound Surveillance, Epidemiology and End Results (SEER) cancer registry.
The investigators found 521 cases of lung cancer.
Adjusting for risk factors including smoking, age, sex, cancer history, other lung disease, and history of lung cancer, the researchers found:
No increased risk with increasing years of multivitamin use for non-small cell lung cancer (P=0.841 for trend), small cell lung cancer (P=0.314 for trend), or other lung cancers (P=0.561 for trend).
No increased risk with increasing daily dose of vitamin C for non-small cell lung cancer (P=0.741 for trend), small cell lung cancer (P=0.224 for trend), or other lung cancers (P=0.182 for trend).
No increased risk with increasing daily dose of folate for non-small cell lung cancer (P=0.366 for trend), small cell lung cancer (P=0.176 for trend), or other lung cancers (P=0.770 for trend).
A small but significant increase in non-small cell lung cancer risk with increasing daily dose of vitamin E (hazard ratio 1.07 per 100 mg/day over 10 years, P=0.004 for trend).
No increase in risk with vitamin E for small cell lung cancer (P=0.396 for trend) or other lung cancers (P=0.981 for trend).
Dr. Slatore on lung cancer prevention
When the researchers further stratified vitamin use by smoking status, they found that there were no associations for multivitamins, vitamin C, or folate.
However, there was an elevation in lung cancer risk with vitamin E among current smokers (HR 1.11 for every 100 mg/day over 10 year, P=0.006 for trend) and not for former smokers.
The results may support the slightly increased mortality risk found for vitamin E supplements in a meta-analysis in the February 28 issue of the Journal of the American Medical Association, Dr. Slatore noted.
But, he cautioned that residual confounding and lack of statistical power might have limited his findings.
While the study suggested that most vitamin supplements are safe with respect to lung cancer, the message for patients should be to focus prevention efforts on improving dietary intake of vitamins, Dr. Slatore concluded.
"What we do know is that fruit and vegetables and a healthy diet do seem to be protective," he said. "What we should do about vitamins is actually less clear."