Letrozole in the Treatment of Severe and Recurrent Endometriosis

Endometriosis is a condition in which abnormal growth of tissue histologically resembling the lining of the uterus (endometrium) is present outside of the uterus. This study will investigate the effect of a daily dose of letrozole compared to GnRH is safe and in addition effective in reducing measurable endometriosis lesions and in reducing pain in patients with active endometriosis which were pretreated with GnRH analogs for 2 months.