Giovannucci E, Rimm E B, Stampfer M J, Colditz G A, Ascherio A, Kearney J, Willett W C
Channing Laboratory, Boston, MA 02115.
J Natl Cancer Inst. 1994 Feb 2;86(3):183-91. doi: 10.1093/jnci/86.3.183.
Epidemiologic studies of men consistently demonstrate a positive association between tobacco smoking and risk of colorectal adenomas, precursors of cancer, but have not consistently shown an association between smoking and colorectal cancer. We hypothesized that smoking acts as an initiator of colorectal neoplasia and that the association with cancer has been obscured because the time is long between onset of smoking and diagnosis of cancer.
Our purpose was to examine the association between cigarette smoking and risk of colorectal adenoma and colorectal cancer in men and to estimate the minimum induction period between the start of smoking and the diagnosis of cancer.
Using data from the ongoing Health Professionals Follow-up Study, we assessed the relative risk (RR) of small adenoma, large adenoma (> or = 1 cm), and cancer according to pack-years of smoking. Current and lifetime histories of smoking and other confounding factors were assessed by questionnaire at baseline and at 2-year intervals. Between 1986 and 1992, we documented 238 new cases of colorectal cancer among 47,935 U.S. males and 626 new cases of colorectal adenomas among 12,854 of the men who had a sigmoidoscopy or colonoscopy.
Smoking during the prior two decades was associated with the prevalence of small adenomas (RR = 2.96; 95% confidence interval [CI] = 1.47-5.98; for > or = 35 pack-years versus 0 pack-years within the 20 years preceding the endoscopy, P trend = .04) but not with large adenomas (RR = 0.46; 95% CI = 0.11-1.94; P trend = .56). However, smoking more than 20 years in the past was associated with large adenomas (RR = 2.38; 95% CI = 1.56-3.63; P trend = .004 for smoking > or = 16 pack-years versus 0 pack-years). Smoking was related to risk of colorectal cancer only after allowing for an induction period of at least 35 years (RR = 1.94; 95% CI = 1.13-3.35; P trend = .008 for smoking > or = 16 versus 0 pack-years more than 35 years in the past).
Smoking in the prior 20 years has a strong relation to small colorectal adenomas, smoking at least 20 years in the past is related to larger adenomas, and the induction period for colorectal cancers is at least 35 years.
Our results highlight the need to intensify efforts to prevent smoking, especially among the young, and suggest a reduced threshold for screening for colorectal cancer among long-term smokers.
针对男性的流行病学研究一致表明，吸烟与结直肠腺瘤（癌症的癌前病变）风险之间存在正相关，但并未始终显示吸烟与结直肠癌之间存在关联。我们推测，吸烟是结直肠肿瘤形成的起始因素，而吸烟与癌症之间的关联之所以被掩盖，是因为从开始吸烟到癌症诊断之间的时间间隔很长。
我们的目的是研究男性吸烟与患结直肠腺瘤和结直肠癌风险之间的关联，并估计开始吸烟到癌症诊断之间的最短诱导期。
利用正在进行的卫生专业人员随访研究的数据，我们根据吸烟包年数评估了小腺瘤、大腺瘤（≥1厘米）和癌症的相对风险（RR）。通过基线及每两年一次的问卷调查评估当前和终生吸烟史以及其他混杂因素。1986年至1992年期间，我们记录了47935名美国男性中的238例新结直肠癌病例以及12854名接受乙状结肠镜检查或结肠镜检查的男性中的626例新结直肠腺瘤病例。
过去二十年中的吸烟与小腺瘤患病率相关（RR = 2.9 6；95%置信区间[CI] = 1.47 - 5.98；在内镜检查前20年内，≥35包年与0包年相比，P趋势 = 0.04），但与大腺瘤无关（RR = 0.46；95% CI = 0.11 - 1.94；P趋势 = 0.56）。然而，过去吸烟超过20年与大腺瘤相关（RR = 2.38；95% CI = 1.56 - 3.63；对于过去吸烟≥16包年与0包年相比，P趋势 = 0.004）。仅在考虑至少35年的诱导期后，吸烟与结直肠癌风险相关（RR = 1.94；95% CI = 1.13 - 3.35；对于过去35年以上吸烟≥16包年与0包年相比，P趋势 = 0.008）。
过去20年的吸烟与小的结直肠腺瘤密切相关，过去吸烟至少20年与较大的腺瘤相关，结直肠癌的诱导期至少为35年。
我们的结果凸显了加大预防吸烟力度的必要性，尤其是在年轻人中，并建议降低长期吸烟者中结直肠癌筛查的阈值。
