Therapeutic effects of leuprorelin microspheres in prostate cancer

Leuprorelin has demonstrated effectiveness comparable to orchiectomy and oral diethylstilboestrol for the palliation of advanced prostate cancer. Unlike orchiectomy, leuprorelin's effects are reversible; also leuprorelin is not associated with the cardiovascular or thromboembolic adverse effects of oestrogens. For these reasons, leuprorelin has been widely used as an alternative to surgical castration or to oestrogens in the treatment of metastatic prostate cancer. Sustained-release leuprorelin microsphere formulations have been developed which exhibit zero order release of active drug from the injection site, such that in the United States the 7.5 mg dosage strength is recommended to be administered once a month and the 22.5 mg dosage strength once every three months. Although most patients will have suppressed release of pituitary luteinizing hormone by the third or fourth week after the first dose of depot leuprorelin, 4-5% of treated patients have been reported to have delayed responses, taking many more weeks or months to respond. A transient biochemical hormone escape has also been reported, although worsening of clinical symptoms has not accompanied the elevation of serum testosterone levels during treatment. Usually, leuprorelin is initiated as monotherapy when patients with advanced prostate cancer become symptomatic. However, newer studies of combination therapy of luteinizing hormone releasing hormone analogs with antiandrogens suggest that early initiation of therapy, at the time of diagnosis of advanced disease, may be beneficial, particularly in a subgroup of patients with small volume disease and good performance status. Leuprorelin is also undergoing evaluation as neoadjuvant therapy prior to radical prostatectomy for localized prostate cancer. Preliminary studies suggest that neoadjuvant leuprorelin in combination with an antiandrogen may be effective in downstaging prostate tumours. Leuprorelin commonly produces several adverse effects: hot flashes, decreased libido and impotence, and tumour flare.