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.
To determine whether vitamins, minerals and other potential agents, alone or in combination, reduce incidence and mortality from lung cancer in healthy people.
The electronic databases MEDLINE (1966-july 2001), EMBASE (1974-july 2001) and the Cochrane Controlled Trial Register (CENTRAL, Issue 3/2001) and bibliographies were searched. In addition authors of included studies were contacted to identify potentially eligible published and unpublished trials.
Included studies were randomised controlled clinical trials comparing different supplements or comparing supplements with placebo, administered to healthy people with the aim of preventing lung cancer.
Data collection and analysis
Three authors independently selected the trials to be included in the review and assessed the methodological quality of each trial, and two extracted data using a standardised form. For each study, relative risk and 95% confidence limits were calculated for dichotomous outcomes.
Four studies were eligible for inclusion. All were population based trials, including a total of 109,394 participants. Two studies included smokers, one included workers exposed to asbestos and two studies were carried out in health professionals. A group of participants with no known risk factors for lung cancer was included in the study sample of two trials. Beta-carotene was evaluated in all trials, alone or combination with alpha-tocopherol or retinol, and one study tested alpha-tocopherol alone. Duration of treatment varied from 2 to 12 years and follow-up was from two to five years. All trials had a placebo group.
For people with risk factors for lung cancer no reduction in lung cancer incidence or mortality was found in those taking vitamins alone compared with placebo (incidence of lung cancer: RR 0.98, 95% CI 0.81-1.19; lung cancer mortality: RR 0.93, 95% CI 0.73-1.19). For people with no known risk factors of lung cancer, none of the vitamins or their combinations appeared to have any effect. Combined data from three studies showed a non-statistically significant increased risk of lung cancer incidence (RR 1.11, 95% CI 0.94-1.33) and mortality (RR 1.05, 95% CI 0.87-1.28) for beta-carotene alone at pharmacological doses in groups with risk factors for lung cancer. When beta-carotene was combined with retinol, data from a single study showed that there was a statistically significant, increased risk of lung cancer incidence (RR 1.42, 95% CI 1.13-1.80) and mortality (RR 1.75, 95% CI 1.29-2.38) in people with risk factors for lung cancer who took both vitamins compared with those who took placebo. Data from also from one study showed that the combination of beta-carotene with alpha-tocopherol in people with risk factors for lung cancer was associated with a non-statistically significant increased risk of lung cancer incidence (RR 1.16, 95% CI 0.96-1.39) and mortality (RR 1.15, 95% CI 0.91-1.45). No effect was observed for total cancer incidence, mortality or all-cause mortality.
There is currently no evidence to support recommending vitamins such as alpha-tocopherol, beta-carotene or retinol, alone or in combination, to prevent lung cancer. A harmful effect was found for beta-carotene with retinol at pharmacological doses in people with risk factors for lung cancer (smoking and/or occupational exposure to asbestos). More research from larger trials and with longer follow-up is needed to analyse the effectiveness of other supplements.
搜尋了書籍和電子資料庫〔MEDLINE 1966年到2001年7月, EMBASE 1974年到2001年7月和the Cochrane Controlled Trial Register (CENTRAL, Issue 3/2001)〕。並且與試驗的作者連絡以確定潛在的合資格的已發表和未發表的試驗。
蒐集了4個符合資格的試驗，都是以人口為基礎的試驗，總共有109394參與者。2個試驗包括了抽菸者，1個試驗包括了石綿暴露工作者，2個試驗的對象是衛生專業人員。1部分的參與者不知道肺癌的危險因素是包括在2個試驗的研究樣本。在所有的試驗中，評估單獨β胡蘿蔔素或是加上α維生素E或是視黃醇的使用，只有1個試驗評估單獨α維生素E的使用。治療時間有2到12年的不同，追蹤時間有2到5年。所有的試驗都有安慰劑組。 在有肺癌危險因子的人中，單獨使用維他命比起安慰劑組沒有降低肺癌的發生率或死亡率(肺癌的發生率：RR 0.98，95% CI 0.81 – 1.19；肺癌死亡率：RR 0.93，95% CI 0.73 – 1.19)。沒有肺癌危險因子的人，維生素或者是其組合沒有任何影響。3個試驗的合併資料顯示單獨使用β胡蘿蔔素的藥用劑量在有肺癌危險因子的組別有非統計學的風險增加肺癌發生率(RR 1.11, 95% CI 0.94 – 1.33)和死亡率(RR 1.05, 95% CI 0.87 – 1.28)。當β胡蘿蔔素合併視黃醇，1個試驗得到的結果顯示在有肺癌危險因子的組別使用2種維生素或者是安慰劑都有統計顯著增加的肺癌發生率(RR 1.42, 95% CI 1.13 – 1.80)和死亡率(RR 1.75, 95% CI 1.29 – 2.38)。同樣從1個試驗得到的結果顯示在有肺癌危險因子的組別合併使用β胡蘿蔔素和α維生素E有非統計學的風險增加肺癌發生率(RR 1.16, 95% CI 0.96 – 1.39)和死亡率(RR 1.15, 95% CI 0.91 – 1.45)。整體肺癌發生率、死亡率或所有致死因的死亡率沒有影響。
此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。