Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 Nov 1;110(11):1239-1247.
doi: 10.1093/jnci/djy040.

The Effects of Metformin and Weight Loss on Biomarkers Associated With Breast Cancer Outcomes

Ruth E Patterson  1   2 , Catherine R Marinac  3   4 , Dorothy D Sears  1   5   2 , Jacqueline Kerr  1   2 , Sheri J Hartman  1   2 , Lisa Cadmus-Bertram  6 , Adriana Villaseñor  1   2 , Shirley W Flatt  2 , Suneeta Godbole  7 , Hongying Li  7 , Gail A Laughlin  1 , Jesica Oratowski-Coleman  2 , Barbara A Parker  5   2 , Loki Natarajan  1   2
Affiliations

The Effects of Metformin and Weight Loss on Biomarkers Associated With Breast Cancer Outcomes

Ruth E Patterson et al. J Natl Cancer Inst. .

Abstract

Background: This study investigated the effects of metformin and weight loss on biomarkers associated with breast cancer prognosis.

Methods: Overweight/obese postmenopausal breast cancer survivors (n = 333) were randomly assigned to metformin vs placebo and to a weight loss intervention vs control (ie, usual care). The 2 × 2 factorial design allows a single randomized trial to investigate the effect of two factors and interactions between them. Outcomes were changes in fasting insulin, glucose, C-reactive protein (CRP), estradiol, testosterone, and sex-hormone binding globulin (SHBG). The trial was powered for a main effects analysis of metformin vs placebo and weight loss vs control. All tests of statistical significance were two-sided.

Results: A total of 313 women (94.0%) completed the six-month trial. High prescription adherence (ie, ≥80% of pills taken) ranged from 65.9% of participants in the metformin group to 81.3% of those in the placebo group (P < .002). Mean percent weight loss was statistically significantly higher in the weight loss group (-5.5%, 95% confidence interval [CI] = -6.3% to -4.8%) compared with the control group (-2.7%, 95% CI = -3.5% to -1.9%). Statistically significant group differences (ie, percent change in metformin group minus placebo group) were -7.9% (95% CI = -15.0% to -0.8%) for insulin, -10.0% (95% CI = -18.5% to -1.5%) for estradiol, -9.5% (95% CI = -15.2% to -3.8%) for testosterone, and 7.5% (95% CI = 2.4% to 12.6%) for SHBG. Statistically significant group differences (ie, percent change in weight loss group minus placebo group) were -12.5% (95% CI = -19.6% to -5.3%) for insulin and 5.3% (95% CI = 0.2% to 10.4%) for SHBG.

Conclusions: As adjuvant therapy, weight loss and metformin were found to be a safe combination strategy that modestly lowered estrogen levels and advantageously affected other biomarkers thought to be on the pathway for reducing breast cancer recurrence and mortality.

PubMed Disclaimer

Figures

Figure 1.
Figure 1.
Consort diagram for 2 × 2 factorial randomized controlled trial of metformin and weight loss among breast cancer survivors.
Figure 2.
Figure 2.
Effects of metformin and weight loss on mean percent change (95% confidence limits) in breast cancer–related biomarkers among breast cancer survivors in a 2 × 2 factorial randomized controlled trial.
See this image and copyright information in PMC

Comment in

References

    1. Miller KD, Siegel RL, Lin CC, et al. Cancer treatment and survivorship statistics, 2016. CA Cancer J Clin. 2016;66(4):271–289. - PubMed
    1. National Cancer Institute. Cancer stat facts: Female breast cancer. https://seer.cancer.gov/statfacts/html/breast.html. Accessed January 24, 2017.
    1. Goodwin PJ. Obesity and breast cancer outcomes: How much evidence is needed to change practice? J Clin Oncol. 2016;34(7):646–648. - PubMed
    1. Playdon MC, Bracken MB, Sanft TB, et al. Weight gain after breast cancer diagnosis and all-cause mortality: Systematic review and meta-analysis. J Natl Cancer Inst. 2015;107(12):djv275. - PMC - PubMed
    1. Chan DS, Vieira AR, Aune D, et al. Body mass index and survival in women with breast cancer-systematic literature review and meta-analysis of 82 follow-up studies. Ann Oncol. 2014;25(10):1901–1914. - PMC - PubMed

Publication types