Inclusion Criteria:

          1. Participant must have histologically confirmed diagnosis of invasive squamous cell or
             adenocarcinoma of the cervix, FIGO Stage IIIC2 or IV (see Appendix 5 of the currently
             approved protocol).

          2. Participant must have an Eastern Cooperative Oncology Group (ECOG) performance status
             of ≤ 1.

          3. Participant must be ≥ 18 years of age.

          4. Participant must have adequate organ function within 28 days of registration, defined
             as follows:

               -  Absolute neutrophil count ≥ 1,500/µL

               -  Platelets ≥ 100,000/µL

               -  Hemoglobin ≥ 9 g/dL

               -  Serum creatinine ≤ 1.5 x upper limit of normal (ULN) or calculated creatinine
                  clearance ≥ 30 mL/min using the Cockcroft-Gault equation

               -  Total bilirubin ≤ 1.5 x ULN (≤2.0 in patients with known Gilberts syndrome) OR
                  direct bilirubin ≤ 1 x ULN

               -  Aspartate aminotransferase and alanine aminotransferase ≤ 2.5 x ULN unless liver
                  metastases are present, in which case they must be ≤ 5 x ULN

          5. Participant receiving corticosteroids may continue as long as their dose is stable for
             least 4 weeks prior to initiating protocol therapy.

          6. Participant must agree to not donate blood during the study or for 90 days after the
             last dose of study treatment.

          7. Female participant of childbearing potential must have a negative serum pregnancy test
             within 14 days prior to registration. Pregnancy test should be repeated within 7 days
             before CT simulation if more than 14 days has passed since the previous pregnancy
             test. (If serum test is falsely positive, pregnancy can be excluded by appropriate
             pelvic imaging.) Patient must agree to abstain from activities that could result in
             pregnancy from screening through completion of 7 days of pelvic radiotherapy. Females
             of non-childbearing potential is defined as follows (by other than medical reasons):

               -  ≥45 years of age and has not had menses for >1 year

               -  Post-hysterectomy, post-bilateral oophorectomy, post external beam radiation of 6
                  Gy to the pelvis, or post-tubal ligation. Documented hysterectomy or oophorectomy
                  must be confirmed with medical records of the actual procedure or confirmed by a
                  physical exam or imaging.

          8. Participant must agree to not breastfeed during the study and for 180 days after the
             last dose of study treatment.

          9. Participant must be able to understand the study procedures and agree to participate
             in the study by providing written informed consent

         10. Participant must have completed 3-6 cycles of platinum based chemotherapy (acceptable
             regimens in Appendix 7) with clinical evidence of CR (complete response) or PR
             (partial response) by RECIST criteria no less than 4 weeks and no greater than 12
             weeks prior to initiation of protocol therapy. If bevacizumab used, 6 weeks must
             elapse between administration of bevacizumab and start of radiation therapy.

         11. Participant must be eligible for chemoradiation treatment in the opinion of the
             treating investigator.

         12. Participants who are HIV+ must have CD4 counts >200/dL and demonstrate documented
             HAART compliance

         13. Chemotherapy-related hematological toxicities must have resolved to Grade 1 or less.

         14. Participant must have had a CT (chest/abdomen/pelvis) or PET-CT, within 56 days of
             registration

        Exclusion Criteria:

          1. Participant must not be simultaneously enrolled in any interventional clinical trial.

          2. Participant must not have known documented intra-uterine pregnancy.

          3. Participant must not have had major surgery ≤ 3 weeks prior to initiating protocol
             therapy and participant must have recovered from any surgical effects.

          4. Participant must not have received investigational therapy ≤ 4 weeks, or within a time
             interval less than at least 5 half-lives of the investigational agent, whichever is
             shorter, prior to initiating protocol therapy. Participant that has received prior
             treatment with a PARP inhibitor is excluded from this study.

          5. Participant last treatment with platinum based chemotherapy was ≥12 weeks from
             initiation of protocol therapy.

          6. Participant must not receive any additional chemotherapy while on study.

          7. Participant has had radiation therapy encompassing >20% of the bone marrow within 2
             weeks; or any radiation therapy within 1 week prior to Day 1 of protocol therapy.

          8. Participant must not have a known hypersensitivity to niraparib components or
             excipients.

          9. Participant must not have received colony stimulating factors (e.g. granulocyte
             colony-stimulating factor, granulocyte macrophage colony stimulating factor, or
             recombinant erythropoietin) within 4 weeks prior to initiating protocol therapy.

         10. Participant must not have any known history of myelodysplastic syndrome (MDS) or acute
             myeloid leukemia (AML).

         11. Participant must not have a serious, uncontrolled medical disorder, nonmalignant
             systemic disease, or active, uncontrolled infection. Examples include, but are not
             limited to, uncontrolled ventricular arrhythmia, NYHA Class III/IV heart failure,
             recent (within 90 days) myocardial infarction, uncontrolled major seizure disorder, or
             any psychiatric disorder that prohibits obtaining informed consent. Participant must
             not have had a CVA within 6 months of registration.

         12. Participant must not have had diagnosis, detection, or treatment of another type of
             cancer ≤ 2 years prior to initiating protocol therapy (except basal or squamous cell
             carcinoma of the skin that has been definitively treated).