Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library

Goserelin (Zoladex): what the evidence says

Name: Goserelin (Zoladex)
Published: 2026-10-27

At a glance

What it is: a synthetic 10-amino-acid analog of GnRH, given as a small implant under the skin. After an early surge, it shuts down testosterone and estrogen production. Approved as Zoladex (first in Dec 1989) for prostate cancer, advanced breast cancer, endometriosis and thinning the uterine lining before surgery. ^{R1, R2, R3}

What the evidence says: Human adding goserelin to radiotherapy for locally advanced prostate cancer improved 10-year survival (58.1% vs 39.8%). ^R4 In early breast cancer, a Cochrane review of trials (mostly goserelin) found the data supportive of benefit, and adding goserelin after chemotherapy improved disease-free survival in ER-positive disease. ^{R5, R6}

Biggest risks: an initial hormone surge (tumor flare) can briefly worsen symptoms; label warnings also cover high blood sugar and diabetes, heart attack and stroke risk, and use in pregnancy. Prohibited in male athletes. ^{R3, R7}

Rating


Human Human evidence	Strong: multiple RCTs and meta-analyses ^{R4, R5}
Animal Animal / lab evidence	Not reviewed
Regulatory	FDA-approved ^R1 · not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page ^{R8, R9, R10} · prohibited in male athletes (WADA S2.2.1) ^R7
Established human dose	Yes, label dose (see Study details)

Evidence verdict: Prostate cancer: Strong (RCTs with survival data) · Breast cancer: Strong (RCTs) · Endometriosis: Strong (approved use) · Off-label hormone or bodybuilding use: No human data

This page reports what studies used. It is not dosing advice.

Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source

About the evidence: strong long-term RCT data; benefits depend on cancer type and combination therapy.

What is it?

Related pages: leuprolide, triptorelin, histrelin, nafarelin.

Does it work?

Human Prostate cancer (EORTC 22863): 10-year survival 58.1% vs 39.8% with radiotherapy alone. ^R4
Human Breast cancer: a Cochrane review of 14 trials (over 13,000 women) found the data supportive of benefit but too thin for firm comparisons with current standard care. ^R5
Human IBCSG VIII: in ER-positive disease, chemotherapy followed by goserelin gave 12-year disease-free survival of 77% vs 69% (chemo alone) and 68% (goserelin alone). ^R6

Is it safe?

Label warnings: pregnancy, tumor flare, hyperglycemia and diabetes, and cardiovascular disease (heart attack, sudden cardiac death, stroke). ^R3
Hot flashes and sexual side effects are common; the label advises bone-density monitoring before repeat courses for endometriosis. ^R3

Gray-market vials: extra risks

A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe.

Is it legal?

US: FDA-approved, prescription (Zoladex). ^{R1, R2}
Compounding: not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page. ^{R8, R9, R10}
Sport: prohibited at all times in male athletes; WADA names it among the GnRH analogues under S2.2.1. ^R7

Study details

These are amounts researchers used, not recommendations.

Study	People / model	Route	Amount used	Follow-up	Reported	Citation
Bolla 2010 (EORTC 22863)	415 men, locally advanced prostate cancer	SC implant	Per label	3 years with radiotherapy	10-yr survival 58.1% vs 39.8%	PMID 20933466
IBCSG VIII 2011	1,063 pre/perimenopausal women, node-negative breast cancer	SC implant	Per study	18 to 24 months	ER+: 12-yr DFS 77% (CMF then goserelin) vs 69% (CMF) and 68% (goserelin)	PMID 21325445
Cochrane 2009	14 trials, >13,000 women	SC implant (mostly goserelin)	Per study	Varied	Data supportive of benefit; too few trials for firm comparisons	PMID 19821328

Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 27, 2026)

^R1 Drugs@FDA, Zoladex 3.6 (goserelin), application NDA019726 (openFDA drugsfda record checked Oct 27, 2026). https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=NDA019726
^R2 Drugs@FDA, Zoladex 10.8 (goserelin), application NDA020578 (openFDA drugsfda record checked Oct 27, 2026). https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=NDA020578
^R3 Zoladex prescribing information, label published Mar 24, 2026 (DailyMed, checked Oct 27, 2026). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=294b168b-6e5f-4db9-bf70-d599271458b3
^R4 Bolla M, et al. Lancet Oncol. 2010. PMID 20933466
^R5 Goel S, et al. Cochrane Database Syst Rev. 2009. PMID 19821328
^R6 Karlsson P, et al. Ann Oncol. 2011. PMID 21325445
^R7 WADA. The 2026 Prohibited List, S2.2.1, Chorionic Gonadotrophin and Luteinizing Hormone and their releasing factors, naming goserelin, histrelin and nafarelin among the GnRH analogues (prohibited in males). https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
^R8 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
^R9 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
^R10 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks

Disclaimer

This page is for education and harm reduction, not medical advice or a recommendation to use Goserelin (Zoladex). This is a prescription medicine. Use it only under the care of a licensed clinician; do not buy it from research-chemical or gray-market sellers. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).