D'Avanzo B, La Vecchia C, Franceschi S, Gallotti L, Talamini R
Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
Prev Med. 1995 Nov;24(6):571-9. doi: 10.1006/pmed.1995.1091.
Although colorectal cancer is not one of the major tobacco-related cancers, a possible association with tobacco has been suggested following the observation of a relationship between cigarette smoking and colorectal adenomas. The issue of a long latency of tobacco on colorectal carcinogenesis has also been suggested, since elevated relative risks were observed in long-term smokers.
The association between colorectal cancer and cigarette smoking has been investigated using data from a case-control study conducted in northern Italy between 1985 and 1991 on 955 cases of colon and 629 cases of rectal cancer and 2,879 controls in hospital for acute, nonneoplastic, nondigestive tract, nontobacco-related diseases. Odds ratios (OR), and the corresponding 95% confidence intervals, of colorectal cancer according to various measures of tobacco smoking were derived from multivariate models, including terms for sex, age, total calorie intake and selected dietary variables, alcohol consumption, and family history of colorectal cancer.
No association between smoking and colorectal cancer was observed. Compared with people who had never smoked, the overall multivariate OR for colorectal cancer was 0.9 in ex-smokers and 0.7 in current smokers. No relationship was found with number of cigarettes smoked (OR = 0.7 for both < 15 and 15-24, and 0.8 for > or = 25 cigarettes per day), age at starting (OR = 0.7 for < 20, 0.8 for 20-29, and 0.9 for > or = 30 years), duration (OR = 0.8 for < 10, 0.7 for 10-19, 0.8 for 20-29, and 0.7 for > or = 30 years), and time since starting (OR = 0.7, for < 30, 0.8 for > or = 30 years) and since stopping (OR = 1.1 for < 10, 0.7 for > or = 10 years). There was no evidence of a trend in risk with increasing lifelong pack-years (OR for > or = 40 pack-years = 0.8 for colon and rectum), pack-years before age 30 (OR = 0.7 for > or = 20 pack-years), or pack-years after age 30 (OR = 0.8 for > or = 30 pack-years). The results were similar for males and females.
The findings of this study indicate that smoking was not a strong risk factor for colorectal cancer, even after a long induction period.
尽管结直肠癌并非主要的烟草相关癌症，但在观察到吸烟与结直肠腺瘤之间的关系后，有人提出吸烟与结直肠癌可能存在关联。由于长期吸烟者的相对风险升高，也有人提出烟草对结直肠癌发生的潜伏期较长这一问题。
利用1985年至1991年在意大利北部进行的一项病例对照研究的数据，调查结直肠癌与吸烟之间的关联。该研究纳入了955例结肠癌患者、629例直肠癌患者以及2879例因急性、非肿瘤性、非消化道、与烟草无关疾病而住院的对照者。根据吸烟的不同衡量指标，通过多变量模型得出结直肠癌的比值比（OR）及相应的95%置信区间，多变量模型包括性别、年龄、总热量摄入、选定的饮食变量、饮酒量以及结直肠癌家族史等因素。
未观察到吸烟与结直肠癌之间存在关联。与从不吸烟的人相比，既往吸烟者患结直肠癌的总体多变量OR为0.9，当前吸烟者为0.7。未发现与吸烟数量（每天<15支和15 - 24支的OR均为0.7，≥25支的OR为0.8）、开始吸烟年龄（<20岁的OR为0.7，20 - 29岁的OR为0.8，≥30岁的OR为0.9）、吸烟持续时间（<10年的OR为0.8，10 - 19年的OR为0.7，20 - 29年的OR为0.8，≥30年的OR为0.7）、开始吸烟后的时间（<30年的OR为0.7，≥30年的OR为0.8）以及戒烟后的时间（<10年的OR为1.1，≥10年的OR为0.7）存在关联。没有证据表明随着终身吸烟包年数增加（≥40包年时结肠癌和直肠癌的OR均为0.8）、30岁前的吸烟包年数（≥20包年的OR为0.7）或30岁后的吸烟包年数（≥30包年的OR为0.8），风险有上升趋势。男性和女性的结果相似。
本研究结果表明，即使经过较长的诱导期，吸烟也不是结直肠癌的强风险因素。
