This study will evaluate the safety of dostarlimab in combination with carboplatin and paclitaxel followed by monotherapy when administered as a first-line treatment in advanced or recurrent endometrial cancer (EC).

Inclusion Criteria:

• Participant with greater than or equals to (>=) 18 years of age, at the time of signing the informed consent.
• Participant has histologically or cytologically proven EC with recurrent or advanced disease.
• Participant must have primary Stage III or Stage IV disease or first recurrent EC with a low potential for cure by radiation therapy or surgery alone or in combination based on investigator's assessment.
• Eligible for dostarlimab treatment according to the approved prescribing information and the investigator's clinical judgement.
• Woman of childbearing potential (WOCBP) agrees to use contraceptive from screening through at least 180 days after the last dose.
• Negative urine pregnancy test at most 24 hours prior to the first dose of study intervention.
• Capable of giving signed informed consent.
• Participant has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

Exclusion Criteria:

• Participant has had greater than (>) 1 recurrence of endometrial cancer.

• Participant has a concomitant malignancy, or participant has a prior non endometrial invasive malignancy who has been disease-free for less than (<) 3 years or who received any active treatment in the last 3 years for that malignancy.

• Participant has known uncontrolled central nervous system metastases, carcinomatosis meningitis, or both.

• Participant is considered a poor medical risk due to a serious, uncontrolled medical disorder, nonmalignant systemic disease, or active infection requiring systemic therapy.

• Participant has not recovered adequately from AEs or complications from any major surgery prior to starting therapy.

• Participant has not recovered (i.e., to Grade less than or equal to [<=] 1 or to Baseline) from cytotoxic therapy induced AEs or has received transfusion of blood products (including platelets or red blood cells) or administration of colony-stimulating factors (including Granulocyte colony-stimulating factor [G-CSF], Granulocyte macrophage colony-stimulating factor [GM-CSF], or recombinant erythropoietin) within 21 days prior to the first dose of study drug.

• Either the history of hypersensitivity to excipients of the study intervention or to drugs with a similar chemical structure or class of the study intervention.

• Participant has known active hepatitis B (e.g., hepatitis B surface antigen reactive) or hepatitis C (e.g., hepatitis C virus ribonucleic acid [qualitative] is detected).

• Participant has received neo-adjuvant/adjuvant systemic anticancer therapy for primary Stage III or IV disease and:

  • has not had a recurrence or Progressive disease (PD) prior to first dose on the study, or
  • has had a recurrence or PD within 6 months of completing systemic anticancer therapy treatment prior to first dose on the study.

• Participant has received prior therapy with an anti- Programmed death protein 1 (anti-PD-1), anti- Programmed death ligand 1 (anti-PD-L1), or Programmed death ligand 2 (anti PD L2) agent.

• Participant has received prior anticancer therapy (chemotherapy, targeted therapies, radiotherapy, or immunotherapy) within 21 days or <5 times the half life of the most recent therapy prior to study Day 1, whichever is shorter.

• Systemic glucocorticoids for any purpose other than to manage symptoms of suspected irAEs. If medically deemed necessary (e.g., acute asthma or chronic obstructive pulmonary disease exacerbation, prophylaxis for intravenous (IV) contrast if indicated), Investigators are allowed to use their judgment to treat participants with systemic steroids. In such cases, systemic steroids should be stopped at least 24 hours prior to the next dose of study treatment.

• Participant has received, or is scheduled to receive, a live vaccine within 30 days before first dose of study intervention, during study treatment, and for up to 180 days after receiving the last dose of study intervention.

• Participant has a diagnosis of immunodeficiency and is receiving systemic steroid therapy (>10 milligrams [mg] daily prednisone or equivalent) within 7 days prior to the first dose of the study treatment or is receiving any other form of immunosuppressive medication.

• Participant is currently receiving study intervention, or is enrolled or has participated in any other clinical study involving an investigational intervention and received investigational treatment or used an investigational device within 4 weeks of the first dose of dostarlimab.

• Participant is pregnant or breastfeeding or is expecting to conceive children within the projected duration of the study, starting with the screening visit through 180 days after the last dose of study intervention.

• Judgment by the investigator that the participant should not participate in the study if the participant is unlikely to comply with study procedures, restrictions, and requirements.

Adult Indian female participants diagnosed with EC who are eligible to receive first-line systemic therapy for primary advanced or recurrent disease will be enrolled.

Study Sponsor will assess requests from qualified researchers for anonymized individual patient-level data and related study documents. Data sharing is subject to certain criteria, conditions, and exceptions. For further information, refer to https://www.gsk-studyregister.com/gsk-patient-level-data-sharing-july2025.pdf

Anonymized IPD will be made available within 6 months of publication of primary, key secondary and safety results for studies in product with approved indication(s) or terminated asset(s) across all indications.

Anonymized IPD is shared with researchers whose proposals are approved by an Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months but an extension may be granted, when justified, for up to 6 months.

This is an open-label study.