Objective: To evaluate the association between pre-and post-diagnosis body mass index (BMI) and risk of colorectal cancer (CRC) death. Methods: The cohort consisted of 3, 057 CRC patients from Shanghai who were diagnosed from Jan. 1, 2009 to Dec. 31, 2011 and aged from 20 to 74 years. The pre- and post-diagnosis BMI and clinical and lifestyle factors were collected at baseline. Death information was collected using record linkage with the Shanghai Cancer Registry and telephone confirmation during follow-up by the end of 2019. The Cox proportional regression model was used to estimate HR with 95% CI. Results: Analysis by multivariable Cox model showed no association between pre-diagnosis BMI and death risk in both male and female patients. Male patients with a post-diagnosis underweight BMI had an elevated risk of death compared to those in normal weight (HR=1.69, 95% CI: 1.21-2.37), especially in early stage cases. Overweight patients (HR=0.74, 95% CI: 0.61-0.89) and patients with obesity class Ⅰ (HR=0.63, 95% CI: 0.45-0.89)had better survival with decreased risks of death, especially in advanced stage cases. The decreased death risk in patients with obesity class Ⅱ was not significant (HR=0.57, 95% CI: 0.24-1.39). The P(trend) value for decreased risk of death with increased BMI in female patients was statistically significant (P<0.001), and the overweight and obesity class Ⅰ categories had better survival in advanced stage(HR(overweight)=0.62, 95% CI: 0.42-0.93; HR(obesity class Ⅰ)=0.39, 95% CI: 0.16-0.98). Both male and female patients with post-diagnosis BMI loss >2.0 kg/m(2) had an increased death risk when compared with those with stable BMI (change≤1.0 kg/m(2)) between pre- and post-diagnosis. BMI gain after diagnosis did not change death risk. Conclusions: Post-diagnosis BMI in the overweight or obesity class Ⅰ groups might be conducive to prolonging male CRC patients' survival, while underweight might result in poor prognosis. Keeping weight and avoiding excessive weight loss should be suggested for all CRC patients after diagnosis.
目的： 探讨结直肠癌诊断前后体质指数(BMI)与死亡风险的关系。 方法： 利用上海市区2009年1月1日至2011年12月31日诊断的、年龄为20~74岁的3 057例结直肠癌病例队列，通过基线调查收集诊断前后BMI、临床和生活方式等相关信息。采取与上海市肿瘤登记部门记录联动和电话随访相结合的方式确定死亡信息，随访截止时间为2019年12月31日。采用Cox比例回归风险模型计算HR和95%CI。 结果： 多因素Cox回归分析显示，在男、女性结直肠癌患者中诊断前BMI均与死亡风险无关。男性结直肠癌患者诊断后消瘦组较正常组死亡风险增加(HR＝1.69，95% CI：1.21~2.37)，尤其是早期患者；超重和Ⅰ级肥胖组患者的死亡风险较正常组下降，HR分别为0.74(95% CI：0.61~0.89)和0.63(95% CI：0.45~0.89)，主要出现在晚期患者中；Ⅱ级肥胖组死亡风险的下降未达到显著性水平(HR＝0.57，95% CI：0.24~1.39)。在女性结直肠癌患者中，随诊断后BMI增加死亡风险降低的趋势检验有统计学意义(均P<0.001)，在晚期患者中超重和Ⅰ级肥胖组死亡风险降低(HR(超重)＝0.62，95% CI：0.42~0.93；HR(Ⅰ级肥胖)＝0.39，95% CI：0.16~0.98)。与诊断前后BMI稳定者(增减≤1.0 kg/m(2))比较，男、女性结直肠癌患者诊断后BMI减少>2.0 kg/m(2)者，死亡风险均增加；而诊断后BMI增加均不会改变死亡风险。 结论： 男性结直肠癌患者诊断后超重及Ⅰ级肥胖状态可能有利于延长其生存时间，而消瘦则不利于其预后。建议男、女性结直肠癌患者诊断后应尽可能维持原有的体重，避免体重下降过多。.
Keywords: Body mass index; Cohort study; Colorectal neoplasms; Death.