AuthorisedTherapeutic exploratory (Phase II)Interventional

Use of the Checkpoint inhibitor DOstarlimab in the endOmetrial cancer fertility-Sparing trEatment: CHOOSE study.

Womb cancer (also known as endometrial cancer) is usually treated with an operation to remove the womb. While this surgery is often successful, it means a woman can no longer become pregnant. The CHOOSE study is testing an immunotherapy drug called dostarlimab for women with a specific type of womb cancer known as 'MMR-deficient'. Dostarlimab works by helping your body's own immune system find and fight cancer cells. Researchers want to find out if this medicine can clear the cancer completely without surgery. If successful, this could give women a safe way to treat their cancer while protecting their fertility. Taking part involves receiving the medicine, regular hospital check-ups, and scans to monitor how well the treatment works. The study is open to adult women who have recently been diagnosed with this particular form of womb cancer.

At a glance

Status

Authorised

Phase

Therapeutic exploratory (Phase II)

Sponsor

UZ Leuven

Enrolment target

Start

23 Sep 2026

Newly diagnosed endometrial carcinomas of the MMR-deficient molecular subtype

What is this study about?

Womb cancer, also called endometrial cancer, begins in the lining of the womb. The standard treatment is usually a hysterectomy, which is an operation to remove the womb and ovaries. Although this operation is very effective at curing the cancer, it leaves women unable to carry a pregnancy. For younger women who hope to start or grow a family, this can be a difficult and distressing reality.

Researchers are running the CHOOSE study to see if a drug called dostarlimab can offer a safe alternative to surgery. Dostarlimab is a type of immunotherapy. Instead of attacking cancer cells directly like chemotherapy, it 'takes the brakes off' your immune system, helping your natural defences find and destroy the cancer cells.

This trial focuses specifically on womb cancers that are 'MMR-deficient'. This means the cancer cells have a fault in how they repair their DNA, which makes them much easier for immunotherapy drugs like dostarlimab to recognise and attack. Doctors want to see how many women experience a complete disappearance of their cancer after taking the drug, and how long this protection lasts.

Key takeaways

The CHOOSE study is testing an immunotherapy drug called dostarlimab for newly diagnosed womb cancer.
The main goal is to treat the cancer effectively without removing the womb, preserving fertility.
The trial is specifically for women whose cancer cells are 'MMR-deficient'.
Participation involves hospital infusions, regular scans, blood tests, and womb biopsies.
Taking part is voluntary, and you can withdraw at any time.

Who may be eligible?

This study is designed for adult women aged 18 and over who have recently been diagnosed with endometrial (womb) cancer. To take part, your cancer must be tested and confirmed as 'MMR-deficient', which is a specific biological subtype.

Because this trial looks at saving fertility, it is generally aimed at women who wish to keep their womb so they can consider having children in the future.

You might not be able to take part if your cancer has spread beyond the womb, if you have already had certain cancer treatments, or if you have other serious medical conditions that make immunotherapy unsafe for you. Your hospital care team can perform tests to see if your cancer matches the trial's requirements.

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 female aged 18 or older.
I have been newly diagnosed with womb (endometrial) cancer.
My cancer is confirmed to be the 'MMR-deficient' type (or I am willing to be tested).
I hope to keep my womb to preserve my fertility.
I have not yet had surgery to remove my womb.

Answer every question to see your result.

What does participation involve?

If you decide to join the study, you will receive dostarlimab as an intravenous drip (an infusion through a small tube into a vein) at a hospital clinic. Treatments are usually given every few weeks.

During the trial, you will need to attend regular hospital visits for health checks. These include blood tests, physical examinations, imaging scans (such as MRI or ultrasound), and small tissue samples (biopsies) taken from the lining of your womb to see if the cancer is shrinking.

Your doctors will closely monitor your progress to see if the cancer goes away completely. After your treatment ends, you will have regular follow-up appointments for several years to make sure the cancer has not returned and to monitor your general health.

Potential risks and benefits

The main hope of this study is that the medicine will clear the cancer while allowing you to keep your womb, offering a chance to carry a pregnancy in the future. However, there is no guarantee that dostarlimab will work for everyone. Like all medicines, dostarlimab can cause side effects. Because it stimulates the immune system, it can cause tiredness, skin rashes, diarrhoea, or inflammation in organs such as the thyroid, bowels, or lungs. Delaying surgery also carries a small risk that the cancer could grow or spread. Taking part is completely voluntary, and you can choose to leave the study at any time without it affecting the quality of your standard NHS care.

Locations (2)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

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Unverified
Italy
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Unverified
Belgium

Common questions

What is dostarlimab and how does it work?

Dostarlimab is an immunotherapy medicine. It blocks a protein that cancer cells use to hide, helping your body's own immune system recognise and destroy the cancer.

What does 'MMR-deficient' mean?

MMR stands for 'mismatch repair'. MMR-deficient cancer cells have a glitch in how they repair their DNA. This makes them stand out more clearly to the immune system, making immunotherapy particularly promising.

Does this trial guarantee I will be able to have a baby?

No, it cannot guarantee pregnancy. The study aims to clear the cancer while keeping your womb intact, but fertility also depends on many other personal health factors.

What happens if the treatment does not work for me?

Your doctors will monitor you very closely. If scans or biopsies show the cancer is not clearing, your team will stop the trial medicine and discuss standard options with you, such as surgery.

Can I leave the study if I change my mind?

Yes. You are free to withdraw from the trial at any point, for any reason, and your medical team will continue to provide the best available standard care.