A Study of Niraparib in People With Soft Tissue Sarcoma Who Have Changes in Their Tumor DNA

Inclusion Criteria: * Age ≥ 18 years at the time of informed consent * Participants or their legally authorized representatives (LARs) need to be willing to provide written informed consent/assent for the trial * Be willing to comply with treatment protocol * Histologically confirmed unresectable or metastatic soft tissue or uterine sarcoma * Known deleterious or suspected deleterious alteration in at least one of the following prespecified DDR pathway genes: Core Genes Gene Pathway BRCA1 FA/HR BRCA2 FA/HR BRIP1 FA/HR BARD1 FA/HR BLM FA/HR PALB2 FA MRE11 HR NBN HR RAD50 HR/NHEJ RAD51B FA/HR RAD51C HR RAD51D HR RAD52 HR RAD54B HR Other Genes Gene Pathway ABRAXAS1 NHEJ ATM OTHER ATR OTHER CHEK1 OTHER CHEK2 OTHER ERCC4 NER ERCC8 NER FANCA FA FANCC FA FANCD2 FA FANCE FA FANCF FA FANCG FA FANCI FA FANCL FA FANCM FA/HR MDC1 OTHER PARP1 BER RAD23B NER RECQL4 HR RPA1 NER SLX4 FA/HR XRCC2 FA/HR XRCC4 NHEJ XRCC6 NHEJ A= Fanconi Anemia BER = Base Excision Repair NER = Nucleotide Excision Repair HR = Homologous Recombination NHEJ = Non-homologous End Joining * Additional genes may be added to Appendix 18.1 in a study addendum as medical and scientific research and/or diagnostic testing evolves * Alterations of uncertain significance must be approved for inclusion by the Principal Investigator * Performance status of ECOG ≤ 2 * Progressed on at least 1 prior line of systemic therapy. * Patients who decline standard of care first-line syst…