Hormone replacement therapy after breast cancer

Abstract

So far, patient samples in all studies investigating hormone replacement therapy (HRT) after breast cancer have been small. Therefore, HRT should only be used if alternatives such as specifically not contraindicated phytopreparations or selective serotonin reuptake inhibitors (SSRIs) are not effective. This is primarily due to forensic reasons since clinical data on the risk of alternatives (based on present evidence) are even more sparse. Regarding HRT, four prospective randomized studies and at least 15 observational studies after breast cancer are available. Only the HABITS study shows an increased risk of relapse. The authors suggest that this is probably associated with the relatively high number of patients with HRT treatment after ER-positive cancers as well as due to the preferred use of estrogen/progestin-combined preparations. Based on the results of the randomized placebo-controlled study Women's Health Initiative (WHI) as well as of at least 12 observational studies, the progestin component seems to be mainly responsible for the probability of increased diagnosis frequency of primary breast cancer. However, no data are available on the impact of progestin on the use of combined HRT after breast cancer. However, also with estrogen only an increased risk of relapse must be expected and patients should be informed about it. This has to be concluded due to biological plausibility and observational studies although the estrogen-only arm in WHI did not show any increased primary risk. Thus, any form of HRT should only be performed in exceptional cases, and treatment duration should be as short as possible with the lowest effective dose.