Association between cigarette smoking and colorectal cancer sidedness: A multi-center big-data platform-based analysis

Background Sidedness (right/left) of colorectal cancer (CRC) is essential for treatment. Whether carcinogenesis of tobacco varies by sidedness remains unclear. The present study aims to evaluate the sidedness tendency of cigarette smoking and to explore its impact on prognosis. Methods In the multi-center retrospective study, data on 46 166 Chinese CRC patients were extracted from a big-data platform. Logistic regression analyses were performed to evaluate qualitative and quantitative associations between smoking and tumor sidedness. Survival analyses were conducted in metastatic CRC. Results History of smoking was associated with left-sided CRC (LSCRC; Adjusted odds ratio, 1.25; 95% CI, 1.16 - 1.34; P < .001). The sidedness tendency towards LSCRC increased from non-smokers, to ex-smokers, and to current smokers (P for trend < .001). Longer duration (P for trend < .001) and larger total amount of cigarette smoking (P for trend < .001) were more associated with LSCRC, respectively. The association was confirmed in both left-sided colon cancer and rectal cancer, but was stronger for rectal cancer (P = .016). Alcoholism significantly enhanced the association by 7% (P = .027). Furthermore, prognostic advantage of metastatic LSCRC diminished among ever-smokers, with contrary survival impacts of smoking on either side of CRC. Conclusions History of smoking was associated with LSCRC in a positive dose-response relationship, and presented opposite prognostic impacts on right- and left-sided tumors. Smoking potentially plays an instrumental role in the mechanism for sidedness heterogeneity in CRC.

Automated summary

The study found a positive association between smoking history and left-sided colorectal cancer, with opposite prognostic impacts of smoking on right- and left-sided tumors. The longer duration and larger total amount of smoking were more associated with left-sided colorectal cancer.