Study of Dostarlimab in Young Women with Newly Diagnosed MMR‑deficient Endometrial Cancer Who Want to Preserve Fertility

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What is this study about?

The study focuses on endometrial cancer, a type of cancer that begins in the lining of the uterus. Participants have a specific form called MMR-deficient, which means the tumor cells have a problem repairing DNA, making the disease behave differently. The treatment being tested is an immune‑based drug called dostarlimab, given through an intravenous infusion (a drip placed into a vein).

The goal of the trial is to see how well this medication works to shrink or eliminate the cancer in young patients who want to keep the ability to have children. Participants receive the drug at regular visits, and doctors check the uterus with imaging and tissue samples to see if the tumor disappears or gets smaller. A “complete response” means no cancer can be found after treatment.

Additional observations include how many patients show any reduction in tumor size, how long the cancer stays away, and how long any response lasts. The study follows participants over time to collect this information.

1 initial study visit

after joining the study you will have an initial visit where the medical team records your health history, performs a physical examination, and collects blood samples and imaging studies to establish a baseline for your condition.

2 first medication administration

you will receive dostarlimab as an intravenous infusion, which means the medicine is delivered slowly through a vein. the dose is 1000 mg per infusion.

3 scheduled follow‑up visits

at each follow‑up visit defined by the study protocol you will meet the study doctors, undergo repeat blood tests and imaging, and discuss any symptoms you may have.

the purpose of these visits is to monitor how your cancer is responding to the treatment and to check for any side effects.

4 additional medication administrations

during each follow‑up visit you will receive another infusion of dostarlimab at the same dose of 1000 mg, unless the study team decides otherwise based on your health status.

5 assessment of treatment response

the study team will compare the new imaging and laboratory results with the baseline to determine whether the tumor has completely disappeared (complete response) or has shrunk (overall response).

6 monitoring for recurrence and duration of response

throughout the study you will continue to be monitored for any return of cancer (recurrence) and for how long any positive response lasts.

7 final study visit

at the end of the study period you will have a final visit where the investigators perform a last set of assessments to summarize the overall effectiveness of the treatment and to record any long‑term outcomes.

Who Can Join the Study?

Give voluntary written informed consent before any screening procedures are done.
Use a highly effective method of birth control (such as implants, injections, or combined oral pills) or practice complete abstinence from heterosexual intercourse, starting at the screening visit and continuing for at least 4 months after the last dose of the study drug.
Be a woman who is older than 18 years and younger than 45 years and who wants to keep the ability to have children (preserve fertility).
Have a new diagnosis of endometrioid endometrial cancer that is graded as G1 or G2 (low‑grade) and that does not show cancer cells in the lymphatic or blood vessels (no lymphovascular space invasion).
Have imaging that shows the cancer is at an early stage (FIGO stage IA, meaning it has not grown into the uterine muscle or the cervix) as confirmed by a pelvic MRI or an expert‑performed pelvic ultrasound.
Show MMR deficiency or MSI‑high status on the tumor sample. This is determined by laboratory tests such as immunohistochemistry, polymerase chain reaction (PCR), or next‑generation sequencing performed in a certified lab.
Have a negative serum pregnancy test taken within 72 hours before the first dose of the study drug and before each subsequent dose.
Have adequate organ function, meaning:
- White blood cell count (absolute neutrophil count) of at least 1,500 per microliter.
- Platelet count of at least 100,000 per microliter.
- Hemoglobin (a measure of red blood cells) of at least 9 g/dL (or 5.6 mmol/L).
- Kidney function with serum creatinine no higher than 1.5 times the normal limit, or a calculated creatinine clearance of at least 50 mL/min.
- Liver function with total bilirubin no higher than 1.5 times the normal limit, direct bilirubin no higher than the normal limit, and AST/ALT enzymes no higher than 2.5 times the normal limit.
- Blood clotting tests (INR, PT, or aPTT) no higher than 1.5 times the normal limit, unless you are on anticoagulant medication and the test results are within the therapeutic range.

Who Cannot Join the Study?

You have previously received any medication that works by blocking PD‑1, PD‑L1, or PD‑L2 (the immune‑system targets used in some cancer treatments).
You have already taken hormonal fertility‑sparing therapy (FST) for endometrial cancer.
Your doctors have found cancer that has spread outside the uterus.
You have any other health problem that the study doctor believes could put your safety at risk or make it hard for you to follow the study plan.
You have taken any other treatment (past or present) that might endanger your safety or affect the study results.
You have another cancer that got worse or needed active treatment within the past 2 years, except for certain skin cancers (basal cell or squamous cell) that were cured or a very early (in‑situ) cervical cancer.
You have a serious, uncontrolled medical condition, a non‑cancer systemic disease, or an active infection that requires medication affecting the whole body.
You are currently pregnant.
You are breastfeeding and are not willing to stop breastfeeding while receiving the study drug.
You plan to become pregnant at any time from the screening visit through 120 days after the last dose of the study medication.
You have an immune‑system problem (immunodeficiency) or have taken systemic steroids or other immune‑suppressing medicines within 7 days before the first study dose.
You have a known infection with HIV, active hepatitis B or hepatitis C.
You have an active autoimmune disease (where the immune system attacks the body) that needed systemic treatment (such as disease‑modifying drugs, corticosteroids, or other immune‑suppressing medicines) in the past 2 years. Routine hormone replacements like thyroid hormone or insulin do not count.
You have a history of interstitial lung disease (a group of lung disorders that cause scarring).
You have taken part in another trial of an experimental drug or used an experimental device within 4 weeks before the first study dose.
You have not fully recovered (still have more than Grade 1 symptoms) from side effects or complications of major surgery before starting the study drug.
You received a live vaccine (e.g., measles, mumps, rubella) within 30 days before the planned start of the study treatment.
You are allergic (have a hypersensitivity) to any part of dostarlimab or its ingredients.
You have previously experienced any of the following severe side effects from immunotherapy: a serious immune‑related problem of grade 3 or higher, serious nerve problems (such as myasthenia gravis, encephalitis, Guillain‑Barré syndrome, or transverse myelitis), severe skin reactions (like Stevens‑Johnson syndrome, toxic epidermal necrolysis, or DRESS syndrome), or heart muscle inflammation (myocarditis). Minor lab changes do not count.
You have a significant heart or blood‑vessel disease that was diagnosed or treated within the past 6 months.
You have cirrhosis (scarring of the liver) or an unstable liver or bile‑duct condition, shown by fluid buildup in the abdomen (ascites), brain confusion (encephalopathy), bleeding problems (coagulopathy), low blood protein (hypoalbuminemia), enlarged veins in the esophagus or stomach (varices), or ongoing yellowing of the skin (jaundice). Stable, non‑cirrhotic liver problems (like Gilbert’s syndrome or harmless gallstones) are allowed.

Where you can join this trial?

Verified and Recommended Sites

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Verified Sites

Site Name	City	Country	Status
Katholieke Universiteit te Leuven	Leuven	Belgium

Other Sites

No sites found in this category

Trial status

Country	Status	Recruitment Start
Belgium	Not yet recruiting	31.07.2026

Trial locations

Investigated Drugs:

Dostarlimab

Dostarlimab is a type of immunotherapy called a checkpoint inhibitor. In this study, it is given through an IV to help the body’s immune system recognize and attack cancer cells in young patients who have a specific form of endometrial cancer (dMMR) and want to keep their ability to have children. The drug is being tested to see if it can effectively treat the cancer while allowing fertility‑preserving options.

Investigated Diseases:

Endometrial cancer

Newly diagnosed mismatch repair-deficient endometrial carcinoma – It is a cancer that starts in the lining of the uterus and lacks normal DNA‑repair proteins. Because the cells cannot fix DNA errors, they multiply more quickly. The tumor usually begins as a localized growth but can spread to nearby tissues or the abdominal lining if it grows unchecked. The disease is identified by testing for loss of mismatch repair proteins. It often occurs in younger women who may wish to preserve fertility.

Trial ID:

2023-509535-11-00

Protocol code:

S68384

Trial Phase:

Therapeutic exploratory (Phase II)

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Study of Dostarlimab in Young Women with Newly Diagnosed MMR‑deficient Endometrial Cancer Who Want to Preserve Fertility

What is this study about?

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Who Cannot Join the Study?