Greenberg E R, Baron J A, Stukel T A, Stevens M M, Mandel J S, Spencer S K, Elias P M, Lowe N, Nierenberg D W, Bayrd G
Dartmouth Medical School, Hanover, N.H.
N Engl J Med. 1990 Sep 20;323(12):789-95. doi: 10.1056/NEJM199009203231204.
Beta carotene has been associated with a decreased risk of human cancer in many studies employing dietary questionnaires or blood measurements, and it has had protective effects in some animal models of carcinogenesis.
We tested the possible cancer-preventing effects of beta carotene by randomly assigning 1805 patients who had had a recent nonmelanoma skin cancer to receive either 50 mg of beta carotene or placebo per day and by conducting annual skin examinations to determine the occurrence of new nonmelanoma skin cancer.
Adherence to the prescribed treatment was good, and after one year the actively treated group's median plasma beta carotene level (3021 nmol per liter) was much higher than that of the control group (354 nmol per liter). After five years of follow-up, however, there was no difference between the groups in the rate of occurrence of the first new nonmelanoma skin cancer (relative rate, 1.05; 95 percent confidence interval, 0.91 to 1.22). In subgroup analyses, active treatment showed no efficacy either in the patients whose initial plasma beta carotene level was in the lowest quartile or in those who currently smoked. There was also no significant difference between treated and control groups in the mean number of new nonmelanoma skin cancers per patient-year.
In persons with a previous nonmelanoma skin cancer, treatment with beta carotene does not reduce the occurrence of new skin cancers over a five-year period of treatment and observation.
在许多采用饮食调查问卷或血液检测的研究中，β-胡萝卜素与人类患癌风险降低有关，并且在一些癌症发生的动物模型中具有保护作用。
我们通过随机分配1805例近期患有非黑色素瘤皮肤癌的患者，让他们每天服用50毫克β-胡萝卜素或安慰剂，并进行年度皮肤检查以确定新的非黑色素瘤皮肤癌的发生情况，来测试β-胡萝卜素可能的防癌效果。
对规定治疗的依从性良好，一年后，积极治疗组的血浆β-胡萝卜素中位数水平（每升3021纳摩尔）远高于对照组（每升354纳摩尔）。然而，经过五年的随访，两组在首次发生新的非黑色素瘤皮肤癌的发生率上没有差异（相对率，1.05；95%置信区间，0.91至1.22）。在亚组分析中，积极治疗在初始血浆β-胡萝卜素水平处于最低四分位数的患者或目前吸烟的患者中均未显示出疗效。在每位患者每年新发生的非黑色素瘤皮肤癌的平均数上，治疗组和对照组之间也没有显著差异。
在既往患有非黑色素瘤皮肤癌的人群中，在五年的治疗和观察期内，β-胡萝卜素治疗并不能降低新皮肤癌的发生。
