Department of Radiation Oncology, University of Rochester, Rochester, NY 14642, United States.
Cancer Epidemiol. 2009 Oct;33(3-4):182-8. doi: 10.1016/j.canep.2009.07.004. Epub 2009 Aug 5.
The majority of recent, well-designed studies have shown that long-term cigarette smoking increases colorectal cancer risk, but older studies with shorter durations of exposure often found no association. This study aimed to examine colorectal cancer risk by smoking exposure using data collected in the late-1950s and early-1960s.
This case-control study examined colorectal cancer risk by lifetime smoking history. There were 1365 patients who visited Roswell Park Cancer Institute (RPCI) between 1957 and 1965 diagnosed with primary, incident colorectal cancers that were matched to 4096 malignancy-free controls on gender and age. Odds ratios were calculated using separate logistic regression models for each smoking exposure, while controlling for other tobacco use, county of residence, race, age, gender, and body mass index (BMI).
The adjusted OR for individuals who reported their greatest level of smoking to be more than 1 pack/day was 0.87 (95% CI=0.67-1.15). Among those who smoked 42 or more years, the adjusted OR was 0.89 (95% CI=0.68-1.15) compared to those who never smoked. For individuals who smoked more than 45 pack-years, the OR was 0.92 (95% CI=0.72-1.19). The results did not differ significantly by gender, although men had considerably greater exposure compared to women. Results also did not differ by colorectal sub-site.
No association was found between long-term cigarette smoking and colorectal cancer risk. These results are in accord with studies that followed cohorts throughout the 1950s and 1960s. Methodological limitations, such as missing data on covariates and the higher incidence of smoking-related illness in a hospital setting, may have contributed to the null results found in this study. Prolonged population exposure to cigarettes and perhaps a changing product may explain why more recent studies have reported a positive association between smoking and colorectal cancer.
大多数近期设计良好的研究表明，长期吸烟会增加结直肠癌风险，但暴露时间较短的较早期研究通常没有发现关联。本研究旨在利用 20 世纪 50 年代末和 60 年代初收集的数据，通过吸烟暴露来检查结直肠癌的风险。
本病例对照研究通过终生吸烟史来检查结直肠癌的风险。共有 1365 名患者于 1957 年至 1965 年期间在罗斯威尔公园癌症研究所（RPCI）就诊，被诊断为原发性、偶发性结直肠癌，根据性别和年龄与 4096 名无恶性肿瘤对照相匹配。使用每个吸烟暴露的单独逻辑回归模型计算比值比，同时控制其他烟草使用、居住县、种族、年龄、性别和体重指数（BMI）。
报告最大吸烟量超过 1 包/天的个体的调整比值比为 0.87（95%CI=0.67-1.15）。在吸烟 42 年或以上的人群中，与从不吸烟的人群相比，调整后的比值比为 0.89（95%CI=0.68-1.15）。对于吸烟超过 45 包年的个体，OR 为 0.92（95%CI=0.72-1.19）。结果在性别上没有显著差异，尽管男性的暴露量明显大于女性。结果也不因结直肠亚部位而有所不同。
长期吸烟与结直肠癌风险之间没有关联。这些结果与在整个 20 世纪 50 年代和 60 年代对队列进行随访的研究一致。方法上的局限性，如协变量数据缺失和医院环境中与吸烟相关的疾病发病率较高，可能导致本研究中发现的无效结果。长期的人群暴露于香烟，也许是产品的变化，可能解释了为什么最近的研究报告吸烟与结直肠癌之间存在正相关关系。
