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Original Investigation
January 2018

Fiber Intake and Survival After Colorectal Cancer Diagnosis

Author Affiliations
  • 1Clinical and Translational Epidemiology Unit, Massachusetts General Hospital and Harvard Medical School, Boston
  • 2Division of Gastroenterology, Massachusetts General Hospital, Boston
  • 3Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
  • 4Department of Medical Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts
  • 5Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
  • 6Division of MPE Molecular Pathological Epidemiology, Department of Pathology, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
  • 7Department of Biostatistics, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
  • 8Yale Cancer Center, New Haven, Connecticut
  • 9Department of Medicine, Yale School of Medicine, New Haven, Connecticut
  • 10Department of Medical Oncology, Smilow Cancer Hospital, New Haven, Connecticut
  • 11Channing Division of Network Medicine, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
  • 12Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts
JAMA Oncol. 2018;4(1):71-79. doi:10.1001/jamaoncol.2017.3684
Key Points

Question  Is fiber intake after colorectal cancer diagnosis associated with mortality?

Findings  In this prospective cohort study that included 1575 patients with stage I to III colorectal cancer, higher intake of fiber, especially from cereals, was associated with a lower risk of colorectal cancer–specific and overall mortality. Patients who increased their fiber intake after diagnosis from levels before diagnosis showed better survival; higher intake of whole grains was also associated with favorable survival.

Meaning  Higher fiber intake after the diagnosis of nonmetastatic colorectal cancer may reduce the risk of colorectal cancer–specific and overall mortality.

Abstract

Importance  Although high dietary fiber intake has been associated with a lower risk of colorectal cancer (CRC), it remains unknown whether fiber benefits CRC survivors.

Objective  To assess the association of postdiagnostic fiber intake with mortality.

Design, Setting, and Participants  A total of 1575 health care professionals with stage I to III CRC were evaluated in 2 prospective cohorts, Nurses’ Health Study and Health Professionals Follow-up Study. Colorectal cancer–specific and overall mortality were determined after adjusting for other potential predictors for cancer survival. The study was conducted from December 23, 2016, to August 23, 2017.

Exposures  Consumption of total fiber and different sources of fiber and whole grains assessed by a validated food frequency questionnaire between 6 months and 4 years after CRC diagnosis.

Main Outcomes and Measures  Hazard ratios (HRs) and 95% CIs of CRC-specific and overall mortality after adjusting for other potential predictors for cancer survival.

Results  Of the 1575 participants, 963 (61.1%) were women; mean (SD) age was 68.6 (8.9) years. During a median of 8 years of follow-up, 773 deaths were documented, including 174 from CRC. High intake of total fiber after diagnosis was associated with lower mortality. The multivariable HR per each 5-g increment in intake per day was 0.78 (95% CI, 0.65-0.93; P = .006) for CRC-specific mortality and 0.86 (95% CI, 0.79-0.93; P < .001) for all-cause mortality. Patients who increased their fiber intake after diagnosis from levels before diagnosis had a lower mortality, and each 5-g/d increase in intake was associated with 18% lower CRC-specific mortality (95% CI, 7%-28%; P = .002) and 14% lower all-cause mortality (95% CI, 8%-19%; P < .001). According to the source of fiber, cereal fiber was associated with lower CRC-specific mortality (HR per 5-g/d increment, 0.67; 95% CI, 0.50-0.90; P = .007) and all-cause mortality (HR, 0.78; 95% CI, 0.68-0.90; P < .001); vegetable fiber was associated with lower all-cause mortality (HR, 0.83; 95% CI, 0.72-0.96; P = .009) but not CRC-specific mortality (HR, 0.82; 95% CI, 0.60-1.13; P = .22); no association was found for fruit fiber. Whole grain intake was associated with lower CRC-specific mortality (HR per 20-g/d increment, 0.72; 95% CI, 0.59-0.88; P = .002), and this beneficial association was attenuated after adjusting for fiber intake (HR, 0.77; 95% CI, 0.62-0.96; P = .02).

Conclusions and Relevance  Higher fiber intake after the diagnosis of nonmetastatic CRC is associated with lower CRC-specific and overall mortality. Increasing fiber consumption after diagnosis may confer additional benefits to patients with CRC.

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