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Meta-Analysis
. 2016 Jul 26;5(1):121.
doi: 10.1186/s13643-016-0294-5.

Progesterone vs. synthetic progestins and the risk of breast cancer: a systematic review and meta-analysis

Noor Asi  1   2 , Khaled Mohammed  3 , Qusay Haydour  3   4 , Michael R Gionfriddo  5 , Oscar L Morey Vargas  6 , Larry J Prokop  7 , Stephanie S Faubion  8 , Mohammad Hassan Murad  3
Affiliations
Meta-Analysis

Progesterone vs. synthetic progestins and the risk of breast cancer: a systematic review and meta-analysis

Noor Asi et al. Syst Rev. .

Abstract

Background: Use of menopausal hormonal therapy (MHT)-containing estrogen and a synthetic progestin is associated with an increased risk of breast cancer. It is unclear if progesterone in combination with estrogen carries a lower risk of breast cancer. Limited data suggest differences between progesterone and progestins on cardiovascular risk factors, including cholesterol and glucose metabolism. Whether this translates to differences in cardiovascular outcomes is uncertain. We conducted a systematic review and meta-analysis to synthesize the existing evidence about the effect of progesterone in comparison to synthetic progestins, each in combination with estrogens, on the risk of breast cancer and cardiovascular events.

Methods: We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Scopus through 17 May 2016 for studies that enrolled postmenopausal women using progesterone vs. synthetic progestins and reported the outcomes of interest. Study selection and data extraction were performed by two independent reviewers. Meta-analysis was conducted using the random effects model.

Results: We included two cohort studies and one population-based case-control study out of 3410 citations identified by the search. The included studies enrolled 86,881 postmenopausal women with mean age of 59 years and follow-up range from 3 to 20 years. The overall risk of bias of the included cohort studies in the meta-analysis was moderate. There was no data on cardiovascular events. Progesterone was associated with lower breast cancer risk compared to synthetic progestins when each is given in combination with estrogen, relative risk 0.67; 95 % confidence interval 0.55-0.81.

Conclusions: Observational studies suggest that in menopausal women, estrogen and progesterone use may be associated with lower breast cancer risk compared to synthetic progestin.

Keywords: Breast cancer; Cardiovascular events; Meta-analysis; Progesterone; Synthetic progestins; Systematic review.

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Figures

Fig. 1
Fig. 1
Study selection process. The initial search resulted in 3410 citations. After screening the abstracts, this was limited to 46 potentially relevant articles. These were reviewed in full text by two authors and eventually two cohort studies and one population-based case-control study were included with 44 being excluded
Fig. 2
Fig. 2
Random effects model of breast cancer risk in postmenopausal women receiving estrogen with progesterone vs. synthetic progestins. This figure shows that progesterone was found to be associated with lower breast cancer compared to synthetic progestins in combination with estrogen
See this image and copyright information in PMC

References

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