Effect of tamoxifen treatment on cortisol metabolism and the course of the disease in advanced breast cancer

Twenty‐nine postmenopausal women with advanced breast cancer were treated with Tamoxifen, a non‐steroidal antiestrogen. The effect of the drug on the plasma concentration, production rate, and metabolism of cortisol was measured, and the relationship of the changes in these parameters to the course of the disease was investigated. After six weeks of Tamoxifen treatment the plasma cortisol concentration and the cortisol‐binding globulin concentration increased by 26 and 64%, respectively, but the production rate of cortisol and the urinary excretion of its tetrahydro metabolites THF, ATHF, and THE decreased by 35 and 13%, respectively; all of these changes were statistically significant. When the group consisting of complete or partial responders was compared with one consisting of patients whose disease remained stable or worsened, no significant difference was detected between these two groups in the change in any of the above parameters. It was concluded that any improvement due to Tamoxifen was not related to changes in cortisol metabolism.