Effect of LHRH agonist, Zoladex, on ovarian histology

In a phase I clinical trial Zoladex was used as first line hormonal therapy in premenopausal women with advanced breast cancer. Patients on progression of their disease underwent surgical oöphorectomy. The histology of ovaries from 23 women treated with Zoladex has been compared with the ovaries from 34 patients who, before the clinical trial of Zoladex, underwent surgical oöphorectomy as primary therapy. Both groups show similar follicular phase development. Only 13 per cent of the Zoladex group developed corpora lutea while 58 per cent showed evidence of luteinization in the primary oöphorectomy group (P less than 0.01). Non-neoplastic follicular cysts were seen more often in the ovaries of the Zoladex treated patients than in the primary oöphorectomy group (P less than 0.05). Zoladex appears to arrest not folliculogenesis but follicular maturation with inhibition of ovulation, the follicles subsequently undergoing atresia with follicular cyst formation.