Zoladex (goserelin)
Zoladex is approved for the management of oestrogen-receptor (ER)-positive early and advanced breast cancer in pre- and peri- menopausal women. Zoladex contains the active ingredient goserelin.
Zoladex is an implant that contains the active ingredient goserelin. It is placed under the skin, usually into the abdomen.
The studies submitted by the Sponsor aimed to show that the 10.8 mg Zoladex implant given every 12 weeks was just as effective at lowering oestrogen levels and slowing breast cancer growth as the 3.6 mg Zoladex implant given every 4 weeks. The Sponsor demonstrated this in studies conducted in premenopausal patients with early and advanced oestrogen-receptor (ER)-positive breast cancer.
Consequently, in this application to extend the approved uses of Zoladex, the 10.8 mg Zoladex implant was approved to treat ER-positive early and advanced breast cancer in women who have not reached menopause or who are close to menopause.
Zoladex treats breast cancer by reducing the body's production of oestrogen. This is important in breast cancers that are ER-positive and so use oestrogen as a growth signal.
Zoladex is a gonadotrophin-releasing hormone (GnRH) agonist, meaning it mimics natural GnRH. Unlike natural GnRH which is released in pulses, Zoladex continuously stimulates the pituitary gland, causing it to stop responding effectively to GnRH signals.
As a result, the levels of luteinising hormone and follicle stimulating hormone fall. Both these hormones stimulate oestrogen production. The reduction in the level of these hormones causes the ovaries to produce less oestrogen, a process known as ovarian function suppression.
The reduced levels of oestrogen may slow or stop the growth of ER-positive breast cancer cells.
The submission consisted of two major studies (D8666C00001, D8664C00004) and one smaller supportive study (D8664C00008; not discussed below) that included a total of 490 premenopausal women with breast cancer. The studies compared the effectiveness and safety of the 3.6 mg Zoladex implant given every 4 weeks to the 10.8 mg Zoladex implant given every 12 weeks.
- Study D8666C00001 was conducted in premenopausal women aged 20 years or older with ER-positive breast cancer that was locally advanced or had spread to other parts of the body. In this study, the main measure was progression-free survival (PFS) at 24 weeks. PFS is the length of time patients lived without their cancer getting worse. At Week 24, a similar number of patients in the 10.8 mg group and the 3.6 mg group were progression-free. Oestrogen levels were also reduced to the same extent in both groups at Weeks 12 and 24. These results showed that the 12-weekly 10.8 mg implant worked at least as well as the 4-weekly 3.6 mg implant.
- Study D8664C00004 was conducted in premenopausal patients with early ER-positive breast cancer. It aimed to show whether the 10.8 mg implant reduced oestrogen levels to a similar extent as the 3.6 mg Zoladex implant. The main measure was the amount of oestrogen in the blood from Week 4 to Week 24. The study met its main goal, showing that the 10.8 mg Zoladex implant was just as effective as the 3.6 mg Zoladex implant at reducing oestrogen levels during this time period.
- No new or concerning safety issues were identified in the three studies. The side effects seen with the 10.8 mg dose were generally similar to those seen with the 3.6 mg dose.
- Hot flushes were the most commonly reported side effect in both treatment groups. Other side effects reported in at least 10% of patients in one or more studies included nasopharyngitis (inflammation of the nose and throat), headache, joint pain, muscle and bone stiffness, increased sweating, back pain, dizziness, eczema, difficulty sleeping, reduced skin sensation, absence of periods and weight gain.
The TGA decided that the application provided sufficient evidence to support the safety and effectiveness of the 10.8 mg Zoladex implant for the new indication.
More detailed information on why the TGA approved Zoladex is available in the Australian Public Assesment Report (AusPAR) for Zoladex
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