[Effect of medroxyprogesterone acetate on the cell kinetics in primary breast cancer]

Effect of medroxyprogesterone acetate (MPA) on the breast cancer cell kinetics was investigated by flow cytometry on paraffin-embedded tissues. Nuclear DNA contents were measured in 67 primary cases. MPA, 1,2000 mg/day, was administered orally for two weeks in 12 cases (MPA group) and the remaining cases (n-MPA group) served as the controls, until the day before operation. The DNA histograms were compared between both groups. The mean percentage of G0 + G1 phase was higher and that of S-phase and G2 + M phase, lower, in the MPA group than those in the n-MPA group. Especially in estrogen receptor positive and premenopausal cases, a significant difference was present between both groups. These results suggest that MPA could inhibit DNA synthesis with a delay of the cell cycle progression in human breast cancer.