Phase 3 clinical trial comparing the addition of anastrozole versus tamoxifen to goserelin therapy before surgery for patients with early-stage breast cancer

This phase 3 clinical trial compared the safety and efficacy of two different combination treatments in women with early stage breast cancer: anastrozole (Arimidex) plus goserelin (Zoladex) versus tamoxifen (Nolvadex) plus goserelin.

An estrogen-receptor positive (ER+) breast cancer requires estrogen (the primary female sex hormone) for the cancer cells to grow. These types of cancer respond to hormone therapy, which prevents the cancer from getting the estrogen it needs to grow. Anastrozole, goserelin and tamoxifen are hormone therapy drugs used to treat ER+ breast cancer patients. Early stage breast cancer is usually treated with surgery, either by removing the whole breast (mastectomy), or by removing just the cancerous lump (lumpectomy). Since ER+ breast cancer responds to hormone therapy, a combination of hormone therapy drugs can be given before surgery to shrink the size of the cancer. This could allow the surgeon to consider a breast-conservation surgery (lumpectomy), instead of a radical treatment (mastectomy). This treatment given before the main therapy for breast cancer (such as surgery) is known as neoadjuvant therapy.

Overall, 197 women with early stage (operable) ER+ breast cancer participated in this 24 week long phase 3 clinical trial. Before surgery to remove the cancer, half of the patients received anastrozole (1 mg/ day) and the other half received tamoxifen (20 mg/day). All patients received goserelin injections of 3.6 mg every 28 days. Efficacy of either treatment was evaluated by extent of cancer shrinkage (complete or partial) and by measuring blood estrogen levels. After 24 weeks of neoadjuvant hormone therapy, 70.4% patients in the anastrozole group had a complete or partial benefit from the treatment as compared to 50.5% in the tamoxifen group. In the anastrozole group, 86% of patients underwent breast-conserving surgery instead of mastectomy compared to 68% for the tamoxifen group. Side effects such as hot flushes, joint pain or headaches were reported in 89% of patients treated with anastrozole and in 86% of those who received tamoxifen.

In summary, the authors of this study found that neoadjuvant treatment with anastrozole and goserelin was more effective than the combination of tamoxifen and goserelin for patients with early-stage ER+ breast cancer.

This treatment holds significant importance for breast cancer patients from a cosmetic and psychological point of view. However, future studies are needed to determine the risk these patients have for the cancer returning after breast conserving surgery.