Benefits of goserelin for early breast cancer persists long-term

NEW YORK (Reuters Health) - The benefit of adjuvant goserelin treatment for early operable breast cancer in premenopausal women is maintained for up to 15 years, according to a follow-up analysis of the ZIPP (Zoladex in Premenopausal Patients) study published in the February 24 online issue of the Journal of the National Cancer Institute.

Previous trials have demonstrated the benefit of reducing circulating estrogen levels with the leuteinizing hormone-releasing hormone agonist goserelin, the authors note.

The ZIPP trial was a randomized, 2-year trial with a 2 x 2 factorial design that included 2706 women below 50 years of age with invasive, operable breast cancer without evidence of metastatic disease. Primary therapy comprised surgery with or without radiotherapy and chemotherapy.

Patients were randomly assigned to tamoxifen alone (20 or 40 mg daily, n = 879), goserelin alone (3.6-mg subcutaneous depot injection into the abdominal wall every 4 weeks, n = 469), goserelin plus tamoxifen (n = 882), or no hormonal therapy (n = 476). Median length of follow-up was 12 years.

The research team, led by Dr. Allan Hackshaw at University College London, observed that "taking either tamoxifen or goserelin had similar and large effects, but using both was associated with a possible small additional benefit that was not statistically significant."

Specifically, goserelin was associated with a 29% reduction in risk of overall mortality, a 34% reduction in risk of recurrence, and 29% reduction in risk of breast cancer mortality. Combining tamoxifen and goserelin was associated with further reductions of 9%-11%.

The small extra effect of adjuvant goserelin among women taking tamoxifen might nonetheless be beneficial. "A difference in risk of 2-3 percentage points in absolute risk at 15 years might be important, given the high incidence of early breast cancer," Dr. Hackshaw's team maintains. "This would correspond to treating 33-50 women with tamoxifen and goserelin to avoid one woman having a recurrence, new tumor, or death."

Another advantage of combined therapy is tamoxifen's ability to prevent the bone loss associated with goserelin treatment.

On the other hand, the authors suggest, "women who are unlikely to complete 5 years of tamoxifen tablets may prefer 2 years of goserelin injections."

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