Peptide education
Goserelin
Goserelin acetate · Zoladex
Goserelin is a prescription medicine that lowers sex hormone levels after an initial rise. Zoladex is a small implant placed under the skin. Its U.S. labels cover selected prostate cancer uses, while the 3.6 mg product also has breast cancer and gynecologic indications.
The condition and implant strength determine how goserelin is used and monitored.
Overview
Quick answer
The 3.6 mg and 10.8 mg implants have different dosing intervals and indications. The 10.8 mg U.S. label covers specified prostate cancer uses; the 3.6 mg label also covers endometriosis, endometrial thinning, and advanced breast cancer in a defined population.
What does goserelin do?
It initially stimulates the pituitary hormone pathway. Continued release from the implant then suppresses that pathway, lowering testosterone or estradiol in the labeled settings.
Which conditions appear in the U.S. labels?
Both strengths have specified prostate cancer indications. The 3.6 mg label also covers endometriosis, endometrial thinning before ablation, and palliative treatment of advanced breast cancer in pre- and perimenopausal women.
How often are the implants given?
For advanced prostate cancer, the labels describe 3.6 mg every 28 days or 10.8 mg every 12 weeks. A labeled regimen with radiation and flutamide begins with 3.6 mg followed by 10.8 mg after 28 days. For endometriosis, the 3.6 mg label recommends a six-month course; the schedule for endometrial thinning before ablation is different.
What deserves attention at the start?
An initial hormone rise can temporarily worsen cancer symptoms. The labels also describe bone loss, injection-site injury, and metabolic and cardiovascular risks in patients receiving GnRH agonists.
Evidence
Evidence snapshot
The U.S. labels describe specified prostate cancer uses, including advanced disease and a defined locally confined setting with other treatment.
The 3.6 mg label covers endometriosis and endometrial thinning before ablation. Its endometriosis experience is limited to six months in adults.
In the ZEBRA early breast cancer comparison, results differed between estrogen receptor-positive and receptor-negative tumors.
Claims
Common claims vs evidence
| Claim | Human evidence | Mechanistic evidence | Verdict |
|---|---|---|---|
| Both Zoladex strengths have the same approved uses. | The 3.6 mg label lists prostate cancer, specified gynecologic uses, and advanced breast cancer. The 10.8 mg label lists specified prostate cancer uses. | The labels have different scopes and dosing intervals. | |
| Goserelin is equivalent to chemotherapy for every breast cancer. | The ZEBRA study compared goserelin with cyclophosphamide, methotrexate, and fluorouracil (CMF) chemotherapy in pre- or perimenopausal patients with node-positive early breast cancer. It reported non-inferiority for overall survival in the estrogen receptor-positive group, but inferior results with goserelin in the receptor-negative group. | The study's results depend on the population and tumor characteristics. | |
| A GnRH agonist suppresses hormones immediately without an initial rise. | The labels warn that the early increase can temporarily worsen cancer symptoms. | Goserelin first stimulates gonadotropin and sex hormone release. Continued exposure then suppresses the pituitary response. | The initial rise is a relevant part of treatment planning. |
Bottom line
Main takeaway
The implant changes hormone signaling over time; its first effect is not its sustained effect.
Ask the treating team which implant is planned and how the condition and risks will be monitored.
The ZEBRA analysis concerns early node-positive breast cancer, whereas the 3.6 mg U.S. label describes advanced breast cancer.
Identity
What it is
Goserelin is a synthetic ten-amino-acid GnRH analog. Zoladex is supplied as a biodegradable implant placed beneath the skin of the abdominal wall under medical supervision.
The 3.6 mg implant releases medicine over a 28-day period. The 10.8 mg product is labeled for administration every 12 weeks in advanced prostate cancer. A combination regimen for locally confined prostate cancer has a different starting sequence.
Use context
Routes, doses, and cycle patterns
The labeled schedule depends on the Zoladex strength and the reason for treatment. The treating clinician coordinates administration and monitoring.
Human studies and product labels
Zoladex 3.6 mg
- Purpose
- Labeled prostate cancer, advanced breast cancer, or gynecologic uses
- Context
- U.S. 3.6 mg product label
- Route
- Subcutaneous implant
- Amount
- 3.6 mg
- Frequency
- Every 28 days
- Duration
- Six months for endometriosis; cancer treatment duration depends on the clinical setting
Before endometrial ablation, the label describes one or two implants, four weeks apart if two are used. Ablation timing depends on whether one or two implants are given.
Zoladex 10.8 mg for advanced prostate cancer
- Purpose
- Palliative treatment of advanced prostate cancer
- Context
- U.S. 10.8 mg product label, advanced prostate cancer
- Route
- Subcutaneous implant
- Amount
- 10.8 mg
- Frequency
- Every 12 weeks
- Duration
- Long-term administration unless clinically inappropriate
The 10.8 mg label does not list the gynecologic or breast cancer indications of the 3.6 mg label.
Zoladex with flutamide and radiotherapy
- Purpose
- Management of locally confined stage T2b to T4 prostate cancer with flutamide and radiation
- Context
- U.S. product labels for stage B2 to C prostate cancer
- Route
- Subcutaneous implants
- Amount
- One 3.6 mg implant followed 28 days later by one 10.8 mg implant
- Frequency
- Treatment begins eight weeks before radiotherapy and continues during radiotherapy
- Duration
- The combination regimen spans the planned radiation treatment
The 3.6 mg label also describes an alternative of four 3.6 mg implants at 28-day intervals, two before and two during radiotherapy.
What varies
- Tumor type and receptor status affect how breast cancer evidence is interpreted.
- The labels include pregnancy restrictions and warnings about fetal harm, with an exception in the 3.6 mg label for palliative treatment of advanced breast cancer.
- The 3.6 mg label says to exclude pregnancy before treatment for benign gynecologic conditions and calls for effective nonhormonal contraception in premenopausal women during treatment and for 12 weeks afterward.
Research
Research evidence
The product labels summarize clinical studies across several indications. A separate ZEBRA analysis compared goserelin with CMF chemotherapy in early breast cancer and reported different outcomes according to estrogen receptor status.
| Study / evidence area | Population | Design | Product context | Main outcome | Limitations | Weight |
|---|---|---|---|---|---|---|
| Prostate cancer implant comparison | 160 patients with advanced prostate cancer | Two controlled trials summarized in the 10.8 mg label | 10.8 mg every 12 weeks versus 3.6 mg every four weeks | The studies compared treatment schedules and testosterone suppression in advanced prostate cancer. | Hormone suppression is not a direct measure of survival, and findings do not establish non-prostate indications for the 10.8 mg implant. | Controlled human studies |
| ZEBRA breast cancer analysis | Pre- or perimenopausal women with node-positive early breast cancer | Randomized comparison of goserelin and CMF chemotherapy | Early breast cancer research | The analysis reported non-inferiority for overall survival in estrogen receptor-positive tumors and inferior outcomes with goserelin in receptor-negative tumors. | Early breast cancer research is distinct from the 3.6 mg label's advanced breast cancer indication. | Controlled human study |
Cautions
Safety and unknowns
- An initial hormone rise can worsen cancer symptoms. The labels call for close attention to people at risk of urinary obstruction or spinal cord compression.
- Bone mineral density can decline during treatment. Hot flashes and sexual or vaginal symptoms can occur as hormone levels fall.
- For endometriosis, the 3.6 mg label does not recommend retreatment because safety data are unavailable. If further treatment is contemplated after symptoms return, it says to consider monitoring bone mineral density.
- Hyperglycemia and cardiovascular events have been reported with GnRH agonists in men. The label calls for attention to blood glucose and cardiovascular risk.
- Implant administration can cause injury or bleeding. The labels also warn about hypersensitivity and severe skin reactions.
- The labels warn that androgen deprivation may prolong the heart's QT interval. They advise clinicians to consider periodic electrocardiograms and electrolyte monitoring, especially when relevant heart conditions, electrolyte abnormalities, or other QT-prolonging medicines are present.
Product quality
Product identity and quality
Zoladex is supplied in a preloaded implant device for administration under medical supervision.
Strength and indication
The two labeled strengths have different schedules and do not share every indication.
Administration
The implant is placed beneath the skin; the labels warn about injection-site injury and bleeding.
Mechanism
How it is proposed to work
Continued goserelin exposure quiets pituitary hormone signaling after an initial stimulatory phase.
The initial rise in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) can raise sex hormones before sustained suppression develops.
The same pathway has different clinical goals in prostate cancer, advanced breast cancer, and endometriosis.
FAQ
Common questions
Do the two Zoladex strengths have the same indications?
No. The 3.6 mg U.S. label includes specified prostate, advanced breast cancer, and gynecologic uses. The 10.8 mg label covers specified prostate cancer uses.
Why can symptoms worsen at the start?
The initial hormone rise can temporarily worsen cancer symptoms. The labels call for attention to risks such as urinary obstruction and spinal cord compression.
How does the implant schedule differ with radiation and flutamide?
For locally confined stage T2b to T4 prostate cancer, the labels describe a 3.6 mg implant followed 28 days later by a 10.8 mg implant, beginning eight weeks before radiation. The 3.6 mg label also describes four 3.6 mg implants at 28-day intervals.
Details
Technical details
Sources
References
- 1.
DailyMed. Zoladex 3.6 mg implant prescribing information
U.S. label for the 3.6 mg implant, its indications, dosing, warnings, and studies.
- 2.
DailyMed. Zoladex 10.8 mg implant prescribing information
U.S. label for the 10.8 mg implant and its prostate cancer indications.
- 3.
PubMed. ZEBRA trial survival analysis: goserelin versus CMF in early breast cancer
doi:10.1016/s0959-8049(03)00392-7 PMID:12888366
Randomized early-breast-cancer comparison with outcomes stratified by estrogen receptor status.