GnRH agonist · prostate & breast cancer
Goserelin is a synthetic version of gonadotropin-releasing hormone (GnRH), the brain signal that drives the testes and ovaries. Given as a small biodegradable implant under the skin, it ends up switching off most sex-hormone production. It is used for prostate cancer, advanced breast cancer, endometriosis, and to thin the uterine lining before ablation1.
Goserelin is a ten-amino-acid analog of GnRH with two altered positions1. It acts on GnRH receptors in the pituitary gland. At first it stimulates them, so testosterone or estrogen briefly rises; this flare can temporarily worsen cancer symptoms in the first weeks. With steady exposure from the implant, the pituitary stops responding and its release of LH and FSH falls, so the testes or ovaries make far less hormone1.
In men with advanced prostate cancer, its hormonal and tumor responses were similar to surgical removal of the testes1. Prostate cancer, many breast cancers and endometriosis lesions depend on these hormones, which is why lowering them can slow or shrink them.
Large randomized trials in people established goserelin in cancer care. In a randomized trial of 415 men with locally advanced prostate cancer, adding goserelin to radiotherapy raised five-year overall survival from 62% to 79%3. In the label's trial of goserelin plus flutamide before and during radiation, local failure at four years fell from 33% to 16%1.
In the ZEBRA trial of premenopausal women with node-positive early breast cancer, goserelin was non-inferior to CMF chemotherapy for survival when tumors were estrogen-receptor-positive, but inferior when they were receptor-negative2. In POEMS, 257 premenopausal women with hormone-receptor-negative breast cancer received chemotherapy with or without goserelin; ovarian failure at two years fell from 22% to 8% and more women later became pregnant (21% versus 11%), though missing data weakened the result4. In endometriosis trials it relieved symptoms about as well as danazol1.
FDA-approved since 1989 as Zoladex implants for prostate cancer; one of its two implant strengths is also approved for advanced breast cancer in pre- and perimenopausal women, endometriosis, and endometrial thinning before ablation1.
In men the label lists hot flashes, sexual dysfunction, reduced erections and urinary symptoms as most common; in women, hot flushes, headache, sweating, acne, mood swings, depression, lower libido, vaginitis and breast shrinkage1. Warnings include tumor flare early on, high blood sugar and diabetes, heart attack and stroke risk in men, high calcium with bone metastases, severe skin reactions, QT prolongation, and injection-site or blood-vessel injury. It can harm a pregnancy.
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