Depot medroxyprogesterone acetate and breast cancer. A review of current knowledge.

Depot medroxyprogesterone acetate (DMPA) has been used worldwide since 1964 as a contraceptive and by 1993 was in use in more than 90 countries. It was licensed for contraceptive use in the US in 1992. One of the reasons for this delay in licensing in the US was the possibility of an increased risk of breast cancer associated with its use. A pooled analysis has recently been published, which brings together the data from 2 large studies of breast cancer risk associated with DMPA use. The overall results are reassuring, but there is some evidence of an increased risk of breast cancer associated with recent use of DMPA. There are substantial difficulties in interpreting this increase in risk. It is certainly possible that it may be the result of surveillance bias, although it could be a short term increase in risk that is not in fact sustained. The conclusion that DMPA should not be restricted as a contraceptive, provided that appropriate advice is given before use, is well-founded. However, further epidemiological work is needed on the long term effects of DMPA.