Safety of hormone therapy after breast cancer: a qualitative systematic review

This qualitative review systematically analyses the safety of hormone therapy (HT) in breast cancer (BC) patients.

We systematically searched studies reporting the use of HT in BC patients. We selected 20 studies in which we evaluated the methodology, characteristics of the studied populations and outcomes in terms of mortality and recurrence rates (RRs).

Many studies evaluating HT were uncontrolled and retrospective. Ten prospective and two randomized studies were found. These were characterized by heterogeneity in populations, tumour characteristics, prognostic factors and treatments. Two studies reported a reduced RR, and two reported lowered BC mortality rates in HT users. One randomized study reported an increased rate of new BC events in HT users.

There are currently no reassuring data indicating the absence of a harmful effect of HT. Further studies should analyse whether some regimens are safer than others. There is a need for randomized trials assessing the safety of these regimens. In the meantime, patients should be informed about the absence of safety data.