Injectable vs Oral Letrozole for Breast Cancer

(SIE-1 Trial)

This trial tests two methods of administering the breast cancer drug letrozole: injection every three months or a daily tablet. Researchers aim to determine how much of the drug enters the bloodstream with each method. The trial targets postmenopausal women who have had hormone receptor-positive early breast cancer and completed at least five years of hormone therapy, including at least two years with letrozole. Participants should currently show no signs of cancer and be in good health. As a Phase 1 trial, the research focuses on understanding how the treatment works in people, offering participants a chance to contribute to early-stage research.

The trial does not specify if you need to stop all current medications, but you cannot use certain hormone therapies or medications that affect specific liver enzymes (CYP3A4 and CYP2A6) within 3 months before starting the trial.

Research has shown that letrozole is generally safe and well-tolerated for treating hormone receptor-positive breast cancer. Studies have found that the pill form's side effects are manageable. One study noted that letrozole caused fewer blood clots compared to tamoxifen. Another study found that a small number of patients taking letrozole experienced bone fractures.

Researchers are excited about these treatments because they explore different delivery methods for letrozole, a key breast cancer medication. While the standard of care typically involves oral tablets like Femara®, this trial is investigating both injectable and EU-sourced oral versions. The injectable form could offer benefits like improved absorption and convenience for those who have difficulty swallowing pills. By comparing these options, the goal is to enhance the effectiveness and patient experience in breast cancer treatment.

This trial will compare the effectiveness of injectable Letrozole SIE with oral Letrozole (Femara®) for treating hormone receptor-positive breast cancer in postmenopausal women. Studies have shown that oral letrozole helps women live longer without cancer recurrence. Specifically, one study found that 93% of women taking oral letrozole remained cancer-free after four years, compared to 87% of those on a placebo. Injectable letrozole, which participants in this trial may receive, is expected to block estrogen similarly, as this hormone can promote the growth of some breast cancers. Early findings suggest that the injectable form might offer the same benefits with potentially fewer side effects.⁶⁷⁸⁹¹⁰