Eligibility Details:  
        Inclusion Criteria:
          -  Patients with a histologically confirmed diagnosis of high-grade nonmucinous
             epithelial ovarian (serous, endometrial, clear cell, carcinosarcoma, an mixed
             pathologies), fallopian tube, or primary peritoneal cancer that is Stage III or IV
             according to the International Federation of Gynecology and Obstetrics (FIGO) or
             tumor, node and metastasis staging criteria.
          -  All patients with Stage IV disease are eligible. This includes those with inoperable
             disease, those who undergo primary debulking surgery (complete cytoreduction (CC0) or
             macroscopic disease), or those for whom neoadjuvant chemotherapy is planned.
          -  Patients with Stage III are eligible if they meet one or more of the following
             criteria:
               1. High risk Stage IIIC disease.
               2. Planning to receive neoadjuvant chemotherapy.
          -  Patients must provide a blood sample for research at Screening.
          -  Patient must provide sufficient tumor tissue sample (a minimum of 2 formalin-fixed
             paraffin embedded blocks) at Screening for research.
          -  Patients must have adequate organ function (Note: complete blood count test should be
             obtained without transfusion or receipt of stimulating factors within 2 weeks before
             obtaining Screening blood sample)
          -  Patients must have an ECOG score of 0 or 1.
          -  Patients must have normal blood pressure (BP) or adequately treated and controlled
             hypertension (systolic BP ≤140 mmHg and/or diastolic BP ≤90 mmHg).
          -  Patients must agree to complete HRQoL questionnaires throughout the study.
          -  Patients must be able to take oral medication.
        Exclusion Criteria:
          -  Patient has mucinous, germ cell, transitional cell, or undifferentiated tumor.
          -  Patient has low-grade or Grade 1 epithelial ovarian cancer.
          -  Stage III patient with complete cytoreduction (CC0) resection after primary debulking
             surgery (ie, no macroscopic residual disease, unless the patient has aggregate 5 cm
             extra-pelvic disease during primary debulking surgery.
          -  Patient has not adequately recovered from prior major surgery.
          -  Patient has a known condition, therapy, or laboratory abnormality that might confound
             the study results or interfere with the patient's participation for the full duration
             of the study treatment in the opinion of the Investigator.
          -  Patient has been diagnosed and/or treated with any therapy for invasive cancer <5
             years from study enrollment, completed adjuvant chemotherapy and/or targeted therapy
             (eg, trastuzumab) less than 3 years from enrollment, or completed adjuvant hormonal
             therapy less than 4 weeks from enrollment. Patients with definitively treated
             non-invasive malignancies such as cervical carcinoma in situ, ductal carcinoma in
             situ, Grade 1 or 2, Stage IA endometrial cancer, or non-melanomatous skin cancer are
             allowed.
          -  Patient is at increased bleeding risk due to concurrent conditions (eg, major injuries
             or major surgery within the past 28 days prior to start of study treatment and/or
             history of hemorrhagic stroke, transient ischemic attack, subarachnoid hemorrhage, or
             clinically significant hemorrhage within the past 3 months).
          -  Patient is immunocompromised. Patients with splenectomy are allowed. Patients with
             well-controlled known human immunodeficiency virus (HIV) are allowed.
          -  Patient has known active hepatitis B (eg, hepatitis B surface antigen reactive) or
             hepatitis C (eg, hepatitis C virus ribonucleic acid [qualitative] is detected).
          -  Patient is considered a poor medical risk due to a serious, uncontrolled medical
             disorder, non-malignant systemic disease, or active, uncontrolled infection.
          -  Patient has had investigational therapy administered within 4 weeks or within a time
             interval less than at least 5 half-lives of the investigational agent, whichever is
             longer, prior to the first scheduled day of dosing in this study.
          -  Patient has received a live vaccine within 14 days of planned start of study therapy.
             Seasonal influenza vaccines that do not contain live viruses are allowed.
          -  Patient has a known contraindication or uncontrolled hypersensitivity to the
             components of paclitaxel, carboplatin, niraparib, bevacizumab, dostarlimab, or their
             excipients.
          -  Prior treatment for high-grade nonmucinous epithelial ovarian, fallopian tube, or
             peritoneal cancer (immunotherapy, anti-cancer therapy, radiation therapy).
          -  Patient has an active autoimmune disease that has required systemic treatment in the
             past 2 years. Replacement therapy is not considered a form of systemic therapy (eg,
             thyroid hormone or insulin).
          -  Patient has a diagnosis of immunodeficiency or is receiving systemic steroid therapy
             or any other form of systemic immunosuppressive therapy within 7 days prior to the
             first dose of study treatment.