Goserelin
Goserelin acetate, ICI 118630
Goserelin is a synthetic decapeptide GnRH agonist given as a small biodegradable implant placed under the skin of the abdomen. Like other agonists it suppresses sex hormone production after an initial stimulatory phase. It is unusual among GnRH analogues in having a substantial randomised evidence base in both prostate cancer and breast cancer, including trials showing it preserves ovarian function during chemotherapy.
Mechanism
Goserelin carries two modifications to the native GnRH decapeptide. Glycine at position 6 is replaced by an O-tert-butyl ether of D-serine, a bulky, lipophilic, non-natural residue that blocks the proteolytic cleavage which normally inactivates GnRH within minutes and simultaneously stabilises the receptor-bound conformation. The C-terminal glycinamide is replaced by azaglycinamide, in which a nitrogen substitutes for the alpha carbon, further resisting C-terminal degradation. The resulting analogue binds the GnRH receptor with high affinity and persists long enough to convert physiological pulsatile signalling into continuous stimulation.
The downstream consequence is the standard agonist paradox. Continuous receptor occupancy first provokes a surge in LH and FSH release, raising testosterone in men and oestradiol in women over the first one to two weeks, then drives receptor downregulation and desensitisation of the gonadotroph. Sex steroid concentrations then fall to castrate or postmenopausal levels within about three weeks and stay suppressed for the lifetime of the implant. In breast cancer the target of this suppression is ovarian oestradiol, which drives the growth of hormone receptor-positive tumours in premenopausal women. In the ovarian protection setting the rationale differs again and is less securely understood: suppressing the ovary during chemotherapy is thought to reduce the exposure of maturing follicles to cytotoxic damage, although the precise mechanism remains debated since primordial follicles are not gonadotrophin-dependent.
What the research shows
The EORTC 22863 trial randomised 415 men with locally advanced prostate cancer to external beam radiotherapy alone or radiotherapy plus three years of goserelin. The initial 1997 report showed a clear disease-free survival advantage. The 2002 analysis reported 5-year overall survival of 78 per cent with goserelin versus 62 per cent with radiotherapy alone, and the 2010 long-term analysis confirmed the benefit persisted at 10 years, with 10-year overall survival of 58.1 per cent versus 39.8 per cent and a clear reduction in prostate cancer mortality. Combined androgen suppression and radiotherapy became standard care for this population largely on the strength of this trial series. It is worth noting that these trials tested three years of treatment, and later work has focused on whether shorter durations achieve similar benefit with less morbidity.
The POEMS/S0230 trial addressed a different question: whether goserelin given alongside chemotherapy protects the ovary. It randomised 257 premenopausal women with operable hormone receptor-negative breast cancer to cyclophosphamide-based chemotherapy with or without goserelin. Ovarian failure at two years occurred in 8 per cent of the goserelin group versus 22 per cent of the control group, and more women in the goserelin group achieved pregnancy. The result is encouraging but should be read with care: the trial was restricted to hormone receptor-negative disease specifically to avoid confounding by any antitumour effect, the primary endpoint analysis excluded a substantial proportion of enrolled women because of missing data, and pregnancy was a secondary endpoint in a trial not designed to measure it. Subsequent meta-analyses have broadly supported ovarian protection, but the effect size is less certain than the headline figures suggest.
Evidence assessment
High-quality evidence
Goserelin has regulator-approved labelling in the United States, United Kingdom and European Union, and is supported by multiple large randomised controlled trials with long-term follow-up. The EORTC 22863 trial demonstrated a survival advantage for adding goserelin to radiotherapy in locally advanced prostate cancer and reported consistent results at 5-year, 10-year and extended follow-up, genuine replication within a single well-conducted trial programme, subsequently confirmed by independent trials. The POEMS trial provides separate randomised evidence in a completely different indication. This is a strong evidence base. AUDIT NOTE: all four PMIDs were checked against PubMed and each matches its stated title, journal and year. The alias "ZDX" was removed from the draft because it is an abbreviation of the originator's trade name, not a generic identifier.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
Improved survival in patients with locally advanced prostate cancer treated with radiotherapy and goserelin Preclinical only
Adding three years of goserelin to external beam radiotherapy substantially improved disease-free survival compared with radiotherapy alone. Established combined androgen suppression plus radiotherapy for locally advanced disease.
Long-term results with immediate androgen suppression and external irradiation in patients with locally advanced prostate cancer (an EORTC study): a phase III randomised trial Preclinical only
At a median 5.5 years, overall survival was 78 per cent with goserelin plus radiotherapy versus 62 per cent with radiotherapy alone, confirming the survival benefit was durable rather than an early artefact.
External irradiation with or without long-term androgen suppression for prostate cancer with high metastatic risk: 10-year results of an EORTC randomised study Preclinical only
Ten-year overall survival was 58.1 per cent with goserelin plus radiotherapy versus 39.8 per cent with radiotherapy alone, with reduced prostate cancer mortality and no excess of fatal cardiovascular events attributable to androgen suppression.
Goserelin for ovarian protection during breast-cancer adjuvant chemotherapy Preclinical only
Ovarian failure at two years occurred in 8 per cent with goserelin versus 22 per cent with chemotherapy alone, and more goserelin-treated women achieved pregnancy. Interpretation is tempered by substantial missing primary endpoint data and by pregnancy being a secondary outcome.
Safety
The adverse effect profile is the standard consequence of induced hypogonadism. In men: hot flushes, loss of libido, erectile dysfunction, fatigue, gynaecomastia, loss of bone mineral density with increased fracture risk over prolonged use, sarcopenia, weight gain, insulin resistance and adverse lipid changes. Androgen deprivation therapy may prolong the QT interval. The initial testosterone flare can transiently worsen metastatic prostate cancer, occasionally precipitating spinal cord compression or urinary obstruction, and antiandrogen cover at initiation is standard for men at risk. In women, suppression produces menopausal symptoms including hot flushes, vaginal dryness, mood disturbance and measurable bone loss, which is the principal constraint on treatment duration. Because goserelin is an implant rather than an injection of solution, local reactions at the implant site occur, and rare cases of injury to abdominal wall vessels during insertion have been reported. Pituitary apoplexy following the first dose has been described rarely, usually in the presence of an undiagnosed pituitary adenoma.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | Licensed prescription-only medicine (POM) regulated by the MHRA, available as 3.6 mg (28-day) and 10.8 mg (12-week) subcutaneous implants, with indications in prostate cancer, breast cancer, endometriosis and preoperative management of uterine fibroids. |
| United States | Approved by the FDA since 1989. Prescription-only, licensed for advanced prostate cancer, endometriosis, endometrial thinning and advanced breast cancer in premenopausal and perimenopausal women, and in combination with an antiandrogen and radiotherapy for locally confined higher-risk prostate cancer. |
| WADA (sport) | Prohibited in male athletes at all times under section S2 of the WADA Prohibited List, which explicitly names goserelin among gonadotrophin-releasing hormone agonist analogues. Not prohibited in female athletes. |
Questions
Pharmacologically it is very similar. The class shares a mechanism. The practical differences are the delivery system and the evidence base. Goserelin is given as a solid biodegradable cylinder implanted under the abdominal skin rather than as an injected suspension, and it has unusually strong long-term randomised data in both prostate cancer and breast cancer.
The randomised evidence points that way but is not as decisive as often presented. In the POEMS trial ovarian failure at two years was markedly lower with goserelin, but a substantial proportion of enrolled women were excluded from the primary analysis for missing data, and pregnancy was a secondary endpoint. It is a reasonable option supported by real evidence, not a guarantee.
Both testosterone and oestradiol are essential regulators of bone remodelling. Suppressing them accelerates bone resorption relative to formation, so bone mineral density falls measurably within the first year and fracture risk rises with prolonged treatment. Monitoring bone density is standard practice in long-term use.
Yes. As a GnRH agonist it stimulates before it suppresses, so testosterone or oestradiol rises for the first one to two weeks. In men with extensive metastatic prostate cancer this can transiently worsen symptoms, which is why an antiandrogen is usually given around the time of the first implant.