BACKGROUND AND PURPOSE:  

• While colorectal cancer (CRC) is trending down in those over 50, incidence and mortality have been increasing in those who are 20 to 49 years of age  
• Liu et al. (JAMA Oncology, 2018) assessed whether obesity and weight gain was associated with higher risk for early-onset colorectal cancer (CRC)

METHODS: 

• Prospective, ongoing cohort study (Nurses’ Health Study II) 
  • US female healthy nurses 
  • No cancer and inflammatory bowel disease 
  • Ages 25 to 42 at study enrollment 
  • Follow-up from 1989 to 2011 
• Data collected including  
  • Current body mass index (BMI)  
  • BMI at 18 years of age 
  • Weight gain since 18 years of age 
• Definitions
  • Overweight: BMI, 25.0-29.9 
  • Obese: BMI, ≥30.0 
• Primary outcome: Association between current BMI and risk of early-onset CRC 
  • Contribution BMI at 18 years of age, weight gain since 18 years of age, and early-life body shape were also analyzed

RESULTS: 

• 85,256 women | 1,196,452 person-years of follow-up 
  • 114 cases of early-onset CRC were documented  
  • Median age at diagnosis: 45 years 
• Compared with women with a BMI of 18.5 to 22.9 
  • Overweight: Relative risk (RR) 1.37 (95% CI, 0.81-2.30)  
  • Obese: 1.93 (95% CI, 1.15-3.25)  
  • RR for each 5-unit increment in BMI was 1.20 (95% CI, 1.05-1.38; P = .01 for trend) 
  • Family history of CRC and without lower endoscopy within the past 10 years did not shift trends 
• Compared with women with a BMI of 18.5 to 20.9 at 18 years of age 
  • BMI of 21.0 to 22.9: RR 1.32 (95% CI, 0.80-2.16)  
  • BMI >23: 1.63 (95% CI, 1.01-2.61; P=.66 for trend)  
• Compared with women who had gained <5.0 kg or had lost weight 
  • 20.0 to 39.9 kg gain: RR 1.65 (95% CI, 0.96-2.81)  
  • ≥40.0 kg gain: RR 2.15 (95% CI, 1.01-4.55; P = .007 for trend)

CONCLUSION: 

• In this study, higher current BMI and weight gain since early adulthood was associated with higher risk for colorectal cancer in women  
• The underlying biologic mechanism remains unclear

Learn More – Primary Sources: 

Association of Obesity With Risk of Early-Onset Colorectal Cancer Among Women

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