Body mass index and risk of second obesity-associated cancers after colorectal cancer: a pooled analysis of prospective cohort studies

J Clin Oncol. 2014 Dec 10;32(35):4004-11. doi: 10.1200/JCO.2014.56.8444. Epub 2014 Sep 29.


Purpose: To determine whether prediagnostic body mass index (BMI) is associated with risk of second obesity-associated cancers in colorectal cancer (CRC) survivors, and whether CRC survivors have increased susceptibility to obesity-associated cancer compared with cancer-free individuals.

Patients and methods: Incident first primary CRC cases (N = 11,598) were identified from five prospective cohort studies. We used Cox proportional hazards regression models to examine associations between baseline (prediagnostic) BMI and risk of second obesity-associated cancers (postmenopausal breast, kidney, pancreas, esophageal adenocarcinoma, endometrium) in CRC survivors, and compared associations to those for first obesity-associated cancers in the full cohort.

Results: Compared with survivors with normal prediagnostic BMI (18.5-24.9 kg/m(2)), those who were overweight (25-29.9 kg/m(2)) or obese (30+ kg/m(2)) had greater risk of a second obesity-associated cancer (n = 224; overweight hazard ratio [HR], 1.39; 95% CI, 1.01 to 1.92; obese HR, 1.47; 95% CI, 1.02 to 2.12; per 5-unit change in BMI HR, 1.12; 95% CI, 0.98 to 1.29). The magnitude of risk for developing a first primary obesity-associated cancer was similar (overweight HR, 1.18; 95% CI, 1.14 to 1.21; obese HR, 1.61; 95% CI, 1.56 to 1.66; per 5-unit change in BMI HR, 1.23; 95% CI, 1.21 to 1.24). Before diagnosis CRC patients were somewhat more likely than the overall cohort to be overweight (44% v 41%) or obese (25% v 21%).

Conclusion: CRC survivors who were overweight or obese before diagnosis had increased risk of second obesity-associated cancers compared with survivors with normal weight. The risks were similar in magnitude to those observed for first cancers in this population, suggesting increased prevalence of overweight or obesity, rather than increased susceptibility, may contribute to elevated second cancer risks in colorectal cancer survivors compared with the general population. These results support emphasis of existing weight guidelines for this high-risk group.

Publication types

  • Multicenter Study
  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Aged
  • Body Composition
  • Body Mass Index*
  • Body Weight
  • Colorectal Neoplasms / complications*
  • Colorectal Neoplasms / diagnosis
  • Female
  • Humans
  • Male
  • Middle Aged
  • Neoplasms, Second Primary / complications*
  • Neoplasms, Second Primary / epidemiology
  • Obesity / complications*
  • Overweight
  • Proportional Hazards Models
  • Prospective Studies
  • Risk Factors
  • Treatment Outcome