Hormone Therapy for Breast Cancer

(POWER II Trial)

This trial explores hormone therapy options for women with early-stage breast cancer before surgery. Researchers will randomly assign participants to one of two groups: one receiving hormone pills (endocrine therapy) for three months before surgery, and the other proceeding directly to surgery. The trial aims to assess how well patients tolerate the hormone treatment and its impact on their overall care experience. Women aged 65 and older with a specific type of breast cancer (ER+) and no significant node involvement may be suitable candidates, particularly if they plan to undergo surgery and can take oral medication. As a Phase 3 trial, this study represents the final step before FDA approval, offering participants a chance to contribute to potentially groundbreaking treatment advancements.

The trial does not specify if you need to stop taking your current medications, but you cannot participate if you are currently using or plan to use strong CYP2D6 inhibitors like Fluvoxamine or Paroxetine.

Research has shown that the treatments tested in this trial—Anastrozole, Exemestane, Letrozole, and Tamoxifen—are generally safe and well-tolerated for breast cancer patients.

Anastrozole significantly lowers the risk of breast cancer recurrence and reduces deaths specifically from breast cancer. It has been used for a long time with positive results.

Exemestane also has a strong safety record. It often works better and is safer than Tamoxifen. Some studies have shown it can reduce the risk of developing invasive breast cancer by 65%.

Letrozole has been studied for safety as well. It has demonstrated high survival rates for patients using it over several years, similar to Anastrozole.

Tamoxifen is well-known for cutting the risk of breast cancer by half in some cases. It also reduces the chance of dying from breast cancer by 57%.

Researchers are excited about the hormone therapies Anastrozole, Exemestane, Letrozole, and Tamoxifen because they offer a tailored approach to treating breast cancer. Unlike chemotherapy, which targets all rapidly dividing cells, these treatments specifically target hormone receptors involved in the growth of certain breast cancer cells. Anastrozole, Exemestane, and Letrozole are aromatase inhibitors that reduce estrogen levels, while Tamoxifen blocks estrogen receptors on cancer cells. This targeted action not only aims to be more effective but also tends to result in fewer side effects compared to traditional chemotherapy.

Research has shown that hormone therapy effectively treats early-stage estrogen receptor-positive (ER+) breast cancer. In this trial, participants in the intervention arm will receive 90 days of pre-endocrine therapy (ET) with either Tamoxifen or an aromatase inhibitor (Anastrozole, Exemestane, or Letrozole) before breast cancer surgery. Anastrozole significantly lowered the chance of cancer recurrence by 41% and reduced breast cancer deaths by 34%. Exemestane showed a 65% reduction in the yearly occurrence of invasive breast cancer in postmenopausal women at higher risk. Letrozole effectively increased the time patients remain cancer-free, with a notable decrease in new tumor development. Tamoxifen demonstrated a 38% reduction in breast cancer cases and a 57% decrease in breast cancer deaths. These treatments generally lower the risk of breast cancer returning and improve survival rates in patients with ER+ breast cancer.¹²⁴⁶⁷