Phytonutrients and outcomes following breast cancer: a systematic review and meta-analysis of observational studies

M. Diana Van Die, Kerry M. Bone, Kala Visvanathan, Cecile Kyrø, Dagfinn Aune, Carolyn Ee, Channing J. Paller

Research output: Contribution to journalReview articlepeer-review

4 Citations (Scopus)
19 Downloads (Pure)

Abstract

Background: Phytonutrient intakes may improve outcomes following breast cancer, but the impact of postdiagnosis introduction vs established prediagnostic exposure as well as optimum doses has not been established. Evidence from observational studies for key exposures was evaluated, including dosage and intake time frames. 

Methods: MEDLINE, EMBASE, CINAHL, Cochrane Library, ClinicalTrials.gov, and the ISRCTN registry were searched for prospective and retrospective observational studies investigating the impact of soybean, lignans, cruciferous (cabbage-family) vegetables, green tea, or their phytonutrients on breast cancer survival outcomes. A random-effects model was used to calculate summary hazard ratios (HRs) and 95% confidence intervals (CIs). Nonlinear dose-response analyses were conducted using restricted cubic splines. 

Results: Thirty-two articles were included. Soy isoflavones were associated with a 26% reduced risk of recurrence (HR = 0.74, 95% CI = 0.60 to 0.92), particularly among postmenopausal (HR = 0.72, 95% CI = 0.55 to 0.94) and estrogen receptor-positive survivors (HR = 0.82, 95% CI = 0.70 to 0.97), with the greatest risk reduction at 60 mg/day. In mortality outcomes, the reduction was mostly at 20 to 40 mg/day. Soy protein and products were inversely associated with cancer-specific mortality for estrogen receptor-positive disease (HR = 0.75, 95% CI = 0.60 to 0.92). An inverse association was observed for serum or plasma enterolactone, measured prediagnosis and early postdiagnosis, with cancer-specific mortality (HR = 0.72, 95% CI = 0.58 to 0.90) and all-cause mortality (HR = 0.69, 95% CI = 0.57 to 0.83). No effects were observed for cruciferous vegetables. There was a 44% reduced risk of recurrence with prediagnostic green tea for stage I and II breast cancer (HR = 0.56, 95% CI = 0.38 to 0.83). 

Conclusions: Soy, enterolactone, and green tea demonstrated significant risk reductions in outcomes following breast cancer. Evidence is needed regarding the impact of postdiagnostic introduction or substantial increase of these exposures.

Original languageEnglish
Article numberpkad104
Number of pages25
JournalJNCI Cancer Spectrum
Volume8
Issue number1
Early online date9 Dec 2023
DOIs
Publication statusPublished - Feb 2024
Externally publishedYes

Keywords

  • soy proteins
  • exposure
  • isoflavones
  • lignans
  • postmenopause
  • vegetables
  • mortality
  • breast cancer
  • phytochemicals
  • enterolactone
  • green tea

Fingerprint

Dive into the research topics of 'Phytonutrients and outcomes following breast cancer: a systematic review and meta-analysis of observational studies'. Together they form a unique fingerprint.

Cite this