20-year follow-up of RCT finds reduced breast cancer death with low-fat diet

  • Chlebowski RT & al.
  • J Clin Oncol
  • 7 Feb 2020

  • curated by Miriam Davis, PhD
  • Univadis Clinical Summaries
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Takeaway

  • A low-fat diet is associated long term with a 21% reduction in breast cancer-attributable deaths.
  • Results are from a randomized controlled trial (RCT) from the US Women's Health Initiative (WHI) with almost 20 years of follow-up.

Why this matters

  • Results suggest that a low-fat diet initiated before breast cancer onset might offer benefit relative to usual diet for reducing breast cancer-attributable deaths.

Study design

  • In the Dietary Modification trial of the WHI, women without breast cancer whose dietary fat intake was ≥32% of energy were randomly assigned to a low-fat diet (dietary fat intake at 20% of energy intake, with more vegetables, fruits, and grains; n=19,541) or to usual diet (fat intake ≥32% of energy; n=29,294) for 8.5 years.
  • Funding: NIH.

Key results

  • At 19.6 years of follow-up, breast cancer incidence did not differ between groups: 
    • HR, 0.95 (95% CI, 0.89-1.02).
  • After a median of 19.6 years, the low-fat group vs the usual-diet group had:
    • Lower death rate after breast cancer:
      • 0.12% vs 0.14% (HR, 0.85; P=.01).
    • Lower death rate attributable to breast cancer:
      • 0.037% vs 0.047% per year (HR, 0.79; P=.02).

Limitations

  • Post hoc analysis.
  • Lack of therapy information.