Michael Cirigliano and Judi Chervenak have stated in reviews of literature on BHT that large-scale, peer-reviewed studies should be used to establish the safety, efficacy and beliefs about the use of bioidentical hormones. Two 2008 studies conducted in France found that estradiol plus micronized progesterone did not increase the incidence of breast cancer, while a comparison of estradiol plus different types of progestins found a reduced risk of invasive breast cancer with micronized progesterone. Christine Derzko stated that the evidence supported the use of bioidentical estrogen plus progesterone, but since the trial was an observational cohort study rather than a randomized controlled trial that compared different types of hormones head-to-head, more data was required before concluding bioidentical hormones were safer and preferred. Derzko concluded that there was weak (but promising) preliminary evidence that bioidentical hormones may present equal (or possibly lower) risks than conventional HRT; however, there was no data supporting the use of compounding. Derzko recommended following evidence-based medicine and cited concerns over BHT by numerous medical organizations—requirements for oversight over compounding, black box warnings for all bioidentical products, and the establishment of a mandatory adverse-events registry.