Although the aetiology of cyclical
mastalgia is poorly understood, the consistent finding of an increased
prolactin stimulation response probably due to oestrogen dominance has led to the use of treatment with
prolactin-lowering drugs and antioestrogens. The efficacy and safety in cyclical
mastalgia of
gestrinone, which has androgenic, anti-oestrogenic, and antiprogestagenic properties, were investigated in a multicentre study. In a double-blind randomisation procedure, 72 patients were allocated placebo and 73 treatment with
gestrinone (2.5 mg twice a week) for 3 months. The patients recorded the severity of
breast pain on a visual analogue scale before and during treatment and scored other breast symptoms as not present (0), mild (1), moderate (2), or severe (3). The
gestrinone group had significantly greater reductions than the placebo group in
breast pain score at months 1, 2, and 3 of treatment (mean reduction 59.5 [SD 22.6] to 11.7 [17.0] vs 58.2 [17.6] to 36.7 [23.0] at month 3; p less than 0.0001). All six breast symptoms had lower scores in the
gestrinone than in the placebo group by the end of treatment. In a subset of 30 participants (15 from each group), serum concentrations of
oestradiol,
progesterone, and tri-iodothyronine were significantly lower than baseline after 3 months of
gestrinone, but concentrations of luteinising
hormone,
follicle-stimulating hormone,
prolactin,
thyroid-stimulating hormone, and
thyroxine did not change. 41% of
gestrinone-treated and 14% of placebo-treated patients reported at least one side-effect; most of these were
androgen-mediated. 11 placebo-treated patients and 4 on
gestrinone discontinued treatment. Thus,
gestrinone was very effective in the treatment of cyclical
mastalgia and was well tolerated.