Objectives: Patterns of disease recurrence on poly(ADP-ribose) polymerase inhibitor maintenance therapy are unclear and may affect subsequent treatment. This ad hoc subgroup analysis of the phase 3 PRIMA/ENGOT-OV26/GOG-3012 study evaluated patterns of initial recurrence in patients with advanced ovarian cancer (AOC)., Methods: PRIMA included participants at high risk for disease progression. This ad hoc analysis only evaluated participants randomized to niraparib maintenance without evidence of disease at baseline. The number and site(s) of initial recurrent lesions at investigator-assessed progressive disease (PD) were evaluated., Results: Of the 314 niraparib-treated patients analyzed, 190 developed ≥1 new lesion (median number of new lesions, 1.0; interquartile range, 1-2). In total, 93.2% (177/190) of patients developed 1-3 lesions at first disease progression. The most common sites of recurrence were the peritoneum (30.0% [57/190]), lymph nodes (26.3% [50/190]), and liver (20.5% [39/190]). Similar results were observed when patients with PD were stratified by biomarker status, disease stage at diagnosis, and type of debulking surgery. Patients with homologous recombination-proficient tumors, stage III disease, or a history of primary debulking developed a median of 2.0 new lesions at first progression; patients with homologous recombination-deficient tumors, stage IV disease, or a history of interval debulking developed a median of 1.0 new lesion., Conclusions: Many patients with AOC without lesions at first-line maintenance treatment initiation develop oligometastatic disease at first recurrence. Prospective evaluation is required to determine whether these patients have improved outcomes when local therapies are combined with continuous, systemic, targeted maintenance therapy., Competing Interests: Declaration of competing interest Mitchell R. Kamrava reports receiving book royalties from Springer, serving on data safety and monitoring boards for Alessa and GT Medical Technologies, and receiving consulting fees from Theragenics and Pfizer. Antonio Gonzalez-Martin reports support from GSK; grants from Roche and TESARO; consulting fees from Alkermes, AstraZeneca, Genmab, ImmunoGen, Novartis, Pfizer/Merck, Roche, Sutro, Amgen, Clovis Oncology, GSK, Merck Sharp & Dohme, Oncoinvent, PharmaMar and Sotio; payment or honoraria from AstraZeneca, PharmaMar, Roche and GSK; and travel support from AstraZeneca, Roche, Pharmamar and GSK. Bhavana Pothuri reports institutional grant support from AstraZeneca, Celsion, Clovis Oncology, Duality Bio, Eisai, Genentech/Roche, Karyopharm, Merck, Mersana, Seagen, Sutro Biopharma, Takeda Pharmaceuticals, Tesaro/GSK, Toray, and VBL Therapeutics; consulting fees from AstraZeneca, BioNtech, Clovis Oncology, Eisai, GOG Foundation, Lily, Merck, Mersana, Seagen, Sutro Biopharma, Tesaro/GSK, Onconova, and Toray; and travel support from GSK and BioNtech. Ignace Vergote reports consulting fees from Agenus, AstraZeneca, Bristol Myers Squibb, Eisai, Genmab, GSK, Immunogen, Karyopharm, Mersana, MSD, Molecular Partners, Novocure, Novartis, Oncoinvent, Regeneron, Seagen, Verastem Oncology, Zai Lab, and Zentalis. Whitney Graybill reports institutional research support from NIH/NCI Cancer Center Support Grant (P30 CA008748) and support grants from ArsenalBio, AstraZeneca/Merck, Atara Biotherapeutics/Bayer, Genentech, Genmab, GSK, Gynecologic Oncology Group (GOG) Foundation, Juno Therapeutics, Kite/Gilead, Ludwig Institute for Cancer Research, Lyell Therapeutics, OnCusp Therapeutics, Regeneron, Sellas Life Sciences, Stemcentrx, Syndax, TapImmune, and TCR2 Therapeutics; participation on advisory boards for Bayer, Carina Biotech, Immunogen, Miltenyi, Loxo, Regeneron, R-Pharm, Seattle Genetics, and Tesaro/GSK; personal fees from GOG Foundation; travel fees from Hitech Health; and service as a noncompensated steering committee member for the DUO-O (olaparib) and PRIMA and Moonstone (niraparib) studies. Colleen McCormick reports participation on advisory boards for GSK, Merck, Immunogen and Clovis. Domenica Lorusso reports medical writing support from Clovis Oncology, GSK, MSD and PharmaMar; institutional funding for work in clinical trials from AstraZeneca, Clovis Oncology, Genmab, GSK, Immunogen, Incyte, MSD, Novartis, PharmaMar, Roche, and Seagen; consulting fees from Amgen, AstraZeneca, Clovis Oncology, Genmab, GSK, Immunogen, MSD, PharmaMar, and Seagen; payment or honoraria from AstraZeneca, Clovis Oncology, GSK, MSD, and PharmaMar; travel for AstraZeneca, Clovis Oncology, GSK, PharmaMar, and Roche; participation on Data Safety Monitoring Boards or advisory boards for AstraZeneca, Clovis Oncology, Corcept, Genmab, GSK, Immunogen, Merck Serono, MSD, Oncoinvent, PharmaMar, Seagen, and Sutro; and is a member of the board of directors for GCIG (no compensation). Gilles Freyer reports consulting fees and payment/honoraria from GSK. David M. O'Malley reports grants from Ajinomoto, BMS, Cerulean Pharma, GOG Foundation, INC Research, InVentiv Health Clinical, Iovance Biotherapeutics, Ludwig Cancer Research, New Mexico Cancer Care Alliance, PRA International, Serono, Stemcentrx, Tracon Pharmaceuticals, and Yale University; has been a consultant/advisory board member for AbbVie, Ambry, Amgen, Array Biopharma, Clovis, EMD Serono, Ergomed, Janssen/Johnson & Johnson, Myriad Genetics, Novocure, Regeneron, Tarveda, and VentiRx; was a member of a steering committee for Genentech/Roche and Merck; and received personal fees from Agenus, Eisai, GSK and Immunogen. Whitney York is an employee of GSK. Izabela A. Malinowska is an employee of GSK. Bradley J. Monk reports consulting fees from Agenus, Akeso Biopharma, Amgen, Aravive, Bayer, Elevar, EMD Merck, Genmab/Seagen, GOG Foundation, Gradalis, ImmunoGen, Iovance, Karyopharm, Macrogenics, Mersana, Myriad, Novartis, Novocure, Pfizer, Puma, Regeneron, Sorrento, US Oncology Research, and VBL; and payment or honoraria from AstraZeneca, Clovis, Eisai, Merck, Roche/Genentech and Tesaro/GSK., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)