Drugs for preventing lung cancer in healthy people

Our plain-English summary of Drugs for preventing lung cancer in healthy people, by M. Cortés-Jofré, J.R. Rueda, G. Corsini-Muñoz, et al (The Cochrane Database of Systematic Reviews, 2012).

The study

• Authors: M. Cortés-Jofré, J.R. Rueda, G. Corsini-Muñoz, C. Fonseca-Cortés, M. Caraballoso, X. Bonfill Cosp
• Journal: The Cochrane Database of Systematic Reviews
• Published: 2012;10:CD002141
• Type of article: Meta-analysis, Systematic review
• Cited by: 38 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: This is an updated version of the original review published in Issue 2, 2003. Some studies have suggested a protective effect of antioxidant nutrients on lung cancer. Observational epidemiological studies suggest an association between higher dietary levels of fruits and vegetables containing beta-carotene and a lower risk of lung cancer.

Objectives: To determine whether vitamins, minerals and other potential agents, alone or in combination, reduce incidence and mortality from lung cancer in healthy people.

Search Methods: For this update we have used a search strategy adapted from the design in the original review. The following electronic databases have been searched up to December 2011: MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL). References included in published studies and reviews were also screened.

Selection Criteria: Included studies were randomised controlled clinical trials comparing different vitamins, mineral supplements or supplements with placebo, administered to healthy people with the aim of preventing lung cancer.

Data Collection And Analysis: Two authors independently selected the trials to be included in the review, assessed the methodological quality of each trial and extracted data using a standardised form. For each study, relative risk and 95% confidence limits were calculated for dichotomous outcomes and pooled results were calculated using the random-effect model.

Main Results: In the first version of this review four studies were included; in this review update, an additional five studies have been included. Four studies included only males and two only females; two studies included only participants considered at high risk, namely smokers or exposed to asbestos, and one study included people deficient in many micronutrients. Six studies analysed vitamin A, three vitamin C, four vitamin E, one selenium supplements, and six studied combinations of two or more products. All the RCTs included in this review were classified as being of low risk of bias.For people not at high risk of lung cancer and compared to placebo, none of the supplements of vitamins or minerals or their combinations resulted in a statistically significant difference in lung cancer incidence or mortality, except for a single study that included 7627 women and found a higher risk of lung cancer incidence for those taking vitamin C but not for total cancer incidence, but that effect was not seen in males or when the results for males and females were pooled.For people at high risk of lung cancer, such as smokers and those exposed to asbestos and compared to placebo, beta-carotene intake showed a small but statistically significant higher risk of lung cancer incidence, lung cancer mortality and for all-causes mortality.

Authors' Conclusions: There is no evidence for recommending supplements of vitamins A, C, E, selenium, either alone or in different combinations, for the prevention of lung cancer and lung cancer mortality in healthy people. There is some evidence that the use of beta-carotene supplements could be associated with a small increase in lung cancer incidence and mortality in smokers or persons exposed to asbestos.

In plain English

This Cochrane systematic review, an update of a 2003 version, pooled randomised placebo-controlled trials testing whether vitamin or mineral supplements prevent lung cancer in healthy people. It included nine trials. The review classed smokers and people exposed to asbestos as high risk, and two trials enrolled only such people. In high-risk people, vitamin A (beta-carotene or retinol) was associated with statistically significantly higher lung cancer incidence (risk ratio 1.11, 95% CI 1.01 to 1.21; four studies, 49,230 participants), lung cancer mortality (1.18, 1.01 to 1.38; two studies) and death from any cause (1.09, 1.05 to 1.13; two studies). In people not at high risk, vitamin A showed no statistically significant differences. Vitamin E, selenium, and vitamin E plus selenium showed none either. One trial of 7627 women found higher lung cancer incidence with vitamin C (1.84, 1.14 to 2.95). The authors said this result should be taken with caution. The authors concluded that beta-carotene could be associated with a small increase in lung cancer incidence and mortality in smokers or people exposed to asbestos.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Systematic review and meta-analysis of randomised placebo-controlled trials (update of a 2003 Cochrane review)
• Who was studied: Nine trials of healthy adults: four from the first version of the review and five added in this update. Two trials enrolled only people considered high risk (smokers or people exposed to asbestos).
• Exposure: Vitamin and mineral supplements versus placebo: vitamin A (beta-carotene or retinol), vitamin C, vitamin E (alpha-tocopherol), selenium, and combinations. Asbestos exposure was used only to classify participants as high risk; no fiber type is named.
• Main results:
  • High-risk people (smokers and those exposed to asbestos), vitamin A versus placebo: lung cancer incidence RR 1.11 (95% CI 1.01 to 1.21), pooled from 4 studies and 49,230 participants.
  • High-risk people, vitamin A versus placebo: lung cancer mortality RR 1.18 (95% CI 1.01 to 1.38), pooled from 2 studies and 29,426 participants.
  • High-risk people, vitamin A versus placebo: all-cause mortality RR 1.09 (95% CI 1.05 to 1.13), pooled from 2 studies and 32,883 participants.
  • People not at high risk: no statistically significant differences between vitamin A and placebo for any outcome, in men, in women, or with both sexes pooled.
  • One trial of 7627 women found a statistically significant higher lung cancer incidence with vitamin C (RR 1.84, 95% CI 1.14 to 2.95). It found no such difference for total cancer incidence.
  • No statistically significant difference between vitamin E and placebo for any outcome.
  • One trial of 17,448 men found no statistically significant difference for selenium versus placebo.
  • One trial of 17,399 men found no statistically significant difference for vitamin E plus selenium versus placebo for any outcome.
  • One trial in a population with nutritional deficiencies tested vitamins A and E with selenium. It found no significant difference in lung cancer mortality. It did find lower all-cancer mortality in women (RR 0.79, 95% CI 0.64 to 0.98) and lower all-cause mortality (RR 0.95, 95% CI 0.91 to 0.99).
• The authors' conclusion: The authors concluded there is no evidence for recommending supplements of vitamins A, C, E or selenium to prevent lung cancer in healthy people. They also concluded there is some evidence that beta-carotene could be associated with a small increase in lung cancer incidence and mortality in smokers or people exposed to asbestos.
• Limitations the authors state:
  • The vitamin C finding in women comes from a single study, and the difference was not statistically significant for men or for both sexes pooled.
  • For selenium and for each combination of products, the evidence comes from a single, different study in each case.
  • For vitamin A and lung cancer incidence in high-risk people, none of the four studies on its own showed a significant difference; only the pooled result did.
  • For vitamin E, the separate data for high-risk people come from a single study.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Clinical Trial, Relative Risk.

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