A Multicenter, Randomized, Double-Blind, Double-Dummy, Phase III Study to Evaluate the Efficacy and Safety of Letrozole SIE Compared to Femara® (both in Combination with the CDK4/6 Inhibitor Ribociclib) in Postmenopausal Women with HR-Positive, HER2-Negative, Inoperable Locally Advanced or Metastatic Breast Cancer (SIE-3)
This study is testing a new, long-acting injection form of letrozole (called Letrozole SIE) for postmenopausal women with advanced breast cancer. Normally, letrozole is taken as a daily tablet (Femara) to block oestrogen and slow cancer growth. Participants will have hormone receptor-positive (HR+) and HER2-negative breast cancer that cannot be removed with surgery or has spread to other areas. Everyone in the trial will receive active treatment. One group receives the new injection plus dummy tablets, while the other receives the standard tablet plus dummy injections. Both groups also take ribociclib, a standard targeted cancer tablet. Researchers want to see if the injection controls the cancer just as effectively as daily tablets, whether it causes fewer joint and muscle pains, and how it affects everyday quality of life.
At a glance
What is this study about?
Many breast cancers need female hormones, such as oestrogen, to grow. These are known as hormone receptor-positive (HR-positive) breast cancers. For women who have gone through the menopause, standard care often includes a medicine called letrozole. It works by lowering the amount of oestrogen the body produces. Today, doctors usually combine letrozole with a targeted therapy called ribociclib to help keep cancer cells from dividing.
Currently, letrozole is taken as a tablet every day. However, remembering daily tablets can be difficult, and the amount of medicine in the blood can rise and fall throughout the day. In this trial, scientists are studying a new version of letrozole that is given as an injection into the muscle. The medicine releases slowly over time, aiming to provide a steady level of treatment.
The main goal of this study is to find out if the injection works just as well as the daily tablet at stopping or slowing cancer growth. Researchers will also look closely at common side effects, especially joint stiffness and muscle aches, to see if the injection is gentler on the body and helps patients maintain a good quality of life.
Key takeaways
- Tests a new long-acting letrozole injection against the standard daily letrozole tablet.
- For postmenopausal women with advanced, HR-positive, HER2-negative breast cancer.
- All participants receive active cancer treatment, including the targeted therapy ribociclib.
- Aims to see if the injection controls cancer as well as tablets while causing fewer joint aches.
- Taking part is voluntary, and you can withdraw at any time.
Who may be eligible?
This trial is designed for adult women who have gone through the menopause and have advanced breast cancer. Advanced cancer means the tumour has grown into nearby tissues so it cannot be removed with surgery, or it has spread to other parts of the body (secondary or metastatic breast cancer).
To be able to take part, your cancer must be hormone receptor-positive (HR-positive) and HER2-negative. This means the cancer cells have receptors for oestrogen or progesterone, but do not produce high levels of the HER2 protein. Your cancer specialist will check your previous tissue tests and scans to confirm these details.
You may not be eligible if you have already had certain treatments for your advanced cancer, or if you have other serious health problems, such as severe heart or liver conditions, that could make taking part unsafe. The hospital study team will check your full medical history with you.
Could this study suit you?
Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.
- I am a woman aged 18 or older.
- I have gone through the menopause.
- I have been diagnosed with advanced or metastatic breast cancer.
- My cancer is confirmed as HR-positive and HER2-negative.
- My cancer cannot be completely removed with surgery.
What does participation involve?
If you decide to join, you will be placed into one of two treatment groups by chance (similar to flipping a coin). To keep the comparison fair, the trial is 'double-blind', meaning neither you nor your doctor will know which letrozole version you are getting. One group receives the real letrozole injection and dummy tablets. The other group receives the real letrozole tablet and dummy injections. Everyone receives active ribociclib tablets.
You will visit the hospital clinic regularly for health reviews, blood tests, and check-ups. You will also have routine imaging scans, such as CT or MRI scans, every few months so the doctors can see how well the treatment is working. You will be asked to complete short questionnaires about your symptoms and daily well-being.
You will stay on the study treatment for as long as it continues to help you and any side effects remain manageable. This could be several months or even years. After finishing the study treatment, the team will continue to check on your health periodically.
Potential risks and benefits
Locations (8)
- —UnverifiedRomania
- —UnverifiedSpain
- —UnverifiedBulgaria
- —UnverifiedCzechia
- —UnverifiedLatvia
- —UnverifiedPoland
- —UnverifiedCroatia
- —UnverifiedSlovakia
Common questions
Will I receive an active treatment for my cancer?
Yes. Every participant in this study receives active cancer medicine. You will either receive the new letrozole injection or standard letrozole tablets, and all participants receive the targeted drug ribociclib.
What is a 'dummy' treatment or placebo?
A dummy treatment looks identical to a real medicine but contains no active ingredients. In this study, dummy injections or dummy tablets are used so that everyone takes both a pill and an injection, ensuring that nobody knows which letrozole type they are receiving.
How is the study injection given?
The injection is given into a muscle (an intramuscular injection), typically in the buttock or thigh, by a trained nurse or doctor during your hospital visit.
Can I leave the trial if I change my mind?
Yes. You have the right to withdraw from the trial at any point, for any reason, without giving an explanation. Your normal medical care will continue as usual.
Will I need to pay for any of the study medicines?
No. All study medications, extra tests, and study-related hospital visits are provided free of charge.
How to find out more
Always speak to your GP or specialist before deciding to take part in a study.
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