RELIABILITY OF IMMUNORADIOMETRIC ASSAYS FOR SEX-HORMONE BINDING GLOBULIN, ANDROSTENEDIONE, 17-BETA ESTRADIOL AND TUMOR-MARKERS CEA AND CB15.3 TO ASSESS THE BIOLOGICAL RESPONSE OF MEGESTROL-ACETATE TREATMENT INPATIENTS WITH ADVANCED BREAST-CANCER

This study evaluated the effect of megestrol acetate administration on the serological assessment of some sex steroid hormones in women with advanced hormone-sensitive breast cancer. The serum levels of 17-beta estradiol, androstenedione and sex hormone binding globulin (SHBG) we re measured by means of radioimmunometric assays, before and during dr ug administration. A significant suppressive effect on SHBG and andros tenedione levels in comparison with the baseline values was reached in 100% (40/40) and 51% (20/39) of patients, respectively, after two mon ths of therapy; by contrast, 17-beta estradiol levels showed an increa se above the baseline levels in 18 out of 22 patients. These findings might be explained on the basis of a possible interference in vivo of megestrol acetate metabolites particularly in the estradiol assay, sin ce a direct influence of the solubilized megestrol acetate was not obs erved in vitro. The hormone levels generally did not shaw any relation ship with the course of the disease, so their serial determinations do not seem to be useful to assess the clinical status or evaluate respo nse to therapy. In our group of patients, CEA and CA15.3 serum determi nations were also carried out to monitor the efficacy of treatment. CE A and CA15.3 levels reflected the course of the disease in 58.9% (23/3 9) and 65.8% (25/38) of patients, respectively. The two tumor markers displayed a similar sensitivity in detecting cancer progression (64% C EA and 63% CA15.3), but CA15.3 seemed to have a better diagnostic valu e in evaluating the response to therapy and signalling tumor relapse.