S433
Clinical - Gynaecological
ESTRO 2026
Radiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand. 6 Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center, Rotterdam, Netherlands. 7 Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, Japan. 8 Radiation Oncology Department, Catalan Institute of Oncology (ICO), University of Barcelona, Hospitalet de Llobregat,, Barcelona, Spain. 9 Dipartimento di Diagnostica per Immaginie Radioterapia Oncologica, Fondazione Policlinico Universitario “A. Gemelli” IRCCS,, Rome, Italy. 10 Department of Radiation Oncology,, UT Southwestern Medical Center, Dallas, USA. 11 Department of Radiation Oncology, Duke Cancer Centre, Durham, USA. 12 Department of Radiotherapy,, Radboud university medical center, Nijmegen, Netherlands. 13 Radiation Medicine Program, Princess Margaret Cancer Center, University Health Network, University of Toronto, Toronto, Canada. 14 Radiotherapiegroep Arnhem, Rijnstate Hospital, Arnhem, Netherlands. 15 Radiation Oncology Unit, Responsible Research Hospital, Campobasso, Italy. 16 Radiotherapy Centre, North Estonia Medical Centre Foundation, Tallinn, Estonia. 17 Department of Radiation Oncology, University Hospital, LMU, Munich, Germany. 18 Division of Radiation Oncology, McGill University Health Centre, Quebec, Canada. 19 Department of Oncology, Cross Cancer Institute, University of Alberta, Edmonton, Alberta, Canada. 20 Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada. 21 Department of Radiation Oncology, University of Toronto, Toronto, Canada. 22 Department of Medical Physics & Informatics, Holland PTC, Delft, Netherlands. 23 Department of Clinical Medicine,, Aarhus University, Aarhus, Denmark Purpose/Objective: Limited evidence exists regarding the post- progression treatment trajectory and survival in patients with oligometastatic or oligo-
recurrent cervical cancer. This study aimed to describe retreatment utilization and sequential progression-free survival. Material/Methods: RetroCOSMOS study (NCT 06150222) registered patients from 18 international centres with synchronous or metachronous oligometastatic or oligo-recurrent cervical cancer treated between 2007-2021. Up to six progressions and up to five courses of (re)treatment were recorded. Patients were categorized into three classes as per protocol A) Synchronous oligometastasis B) Metachronous oligometastasis or C) Oligorecurrent at time of first progression. Within each class (A-C), the proportion receiving retreatments was estimated, including reirradiation. Survival metrics were defined as: disease-free survival (DFS) as time from diagnosis of cervical cancer to first progression. For Class A, DFS represented the median difference from diagnosis to appearance of synchronous metastatic disease. Progression-free survival was time between each successive progression or last follow-up or death (PFS-1–PFS-5). Post- progression survival (PPS) was estimated as the time between first progression and last progression or follow-up or death. Median survival and interquartile ranges (IQR) were estimated, and PPS was analysed using the Kaplan–Meier method. Results: Of the 356 registered patients, 287 patients with complete follow-up were included. Among 287 patients, 37 patients (12.9%) were in Class A, 91(31.7%) in Class B, and 159(55.4%) in Class C. Overall, 129 patients (45%) received one retreatment, whereas 43.2 % (n=114) received 2-3 courses and 11.8% (n=44) received 4-5 retreatment courses. Systemic therapy was administered in 191(69.2%) patients, and pelvic or distant site re-irradiation utilisation was noted in 143 (60.6%) patients. Pembrolizumab was administered in 15 (5.5%) patients and Bevacizumab in 48 (17.5%) patients, not concurrent with RT. Median DFS was 16.3
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