Depot medroxyprogesterone acetate and breast cancer: a systematic review.

PURPOSE:Short-acting progestin-only injectables containing depot medroxyprogesterone acetate (DMPA) are a safe method of contraception. Although DMPA has been available for several decades, there is little data on its influence on the risk of breast cancer. Hence, the aim of this paper was to provide an overview of the existing studies and create clarity regarding a possible association with breast cancer. METHODS:Literature searches were executed in MEDLINE, Embase, the Cochrane Library, ClinicalTrials.gov and ICTRP. Search terms were related to DMPA and breast cancer. After elimination of duplicates, 3'850 studies were identified and assessed according to inclusion and exclusion criteria. Finally, ten studies were selected and included in this review. RESULTS:All the selected papers were case-control-studies, except for one pooled analysis and one study comparing observed and expected number of cancer cases. Most of the included studies found no overall elevated breast cancer incidence in DMPA users, only one study found a slightly increased risk and two studies concluded with a significant increase for the overall breast cancer risk. CONCLUSION:There is little evidence that DMPA may increase the overall risk for breast cancer. However, the incidence of breast cancer is possibly increased in current and more recent users, especially in women younger than 35 years. Long-term use did not result in any risk increase. Nevertheless, further studies will be necessary to confirm these findings and weigh up the individual risks and benefits of this contraceptive method.