ESTRO 2023 - Abstract Book

S682

Monday 15 May 2023

ESTRO 2023

Purpose or Objective Ovarian cancer (OC) represents the most lethal gynaecological malignancy, with approximately 80% of advanced OC patients experiencing a recurrence after primary treatment. The role of radiotherapy in recurrent OC has been recently explored. The aim of this study was to assess the efficacy of advanced radiotherapy at the time of the 1st platinum-sensitive oligometastatic recurrence. Materials and Methods Patients with epithelial OC undergoing primary treatment at the European Institute of Oncology, Milan, from January 2010 to April 2019 were considered for study inclusion. Among those, patients treated with radiotherapy alone at the time of 1st platinum-sensitive oligometastatic recurrence were included. Patients underwent ablative radiotherapy on all oligorecurrent lesions (stereotactic body radiotherapy or intensity modulated radiotherapy). Patients with encephalic or vertebral recurrence were excluded. Response rate (based on RECIST 1.1 criteria), predictor of treatment response, and survival outcome were evaluated. Results In total, 31 patients met the inclusion criteria. Of them, 18 (58,1%) had a complete response, 7 (22,6%) a partial response, and 6 (19.3%) a progressive disease (Table 1.). Among them, 30 (96.8%) had a subsequent relapse, of which 22 (73.3%) were treated with chemotherapy while the remaining 8 (26.7%) underwent re-irradiation or thermoablation. The median interval between radiotherapy and the subsequent recurrence requiring chemotherapy was 16 months (range 4-126), with 18 (58.1%) patients having a subsequent recurrence requiring chemotherapy after 12 months or more. Upon univariate analysis, median platinum-free interval before radiotherapy in patients with complete/partial response was longer than in patients with progressive disease (23 vs. 11 months, p=0.06), although not statistically significant.

Conclusion In our experience, ablative radiotherapy alone represents a valuable option in the treatment of 1st oligometastatic platinum-sensitive recurrent epithelial OC, providing a good response rate and allowing to extend the platinum-free interval. Further studies with longer follow-up are required to confirm our results and identify predictors of treatment response. PD-0810 Pilot study on carbon-ion radiotherapy for recurrent/refractory ovarian/salpinx cancer A. Barcellini 1 , K. Murata 2 , G. Fontana 3 , A. Ghirelli 1 , A. Vai 4 , S. Molinelli 4 , C. Cassani 5 , S. Secondino 6 , G. Baroni 7 , N. Facchinetti 8 , S. Yamada 2 , N. Okonogi 2 , E. Orlandi 1 1 CNAO National Center for Oncological Hadrontherapy, Radiation Oncology Unit, Clinical Department, Pavia, Italy; 2 QST Hospital, National Institutes for Quantum Science and Technology, Radiation Oncology Unit, Chiba, Japan; 3 CNAO National Center for Oncological Hadrontherapy, Clinical Bioengineering Unit, Clinical Department , Pavia, Italy; 4 CNAO National Center for Oncological Hadrontherapy, Medical Physics Unit, Clinical Department, Pavia, Italy; 5 Department of Clinical, Surgical, Diagnostic and Pediatric Sciences, University of Pavia, and Unit of Obstetrics and Gynecology, IRCCS Policlinico San Matteo Foundation, Pavia, Italy; 6 IRCCS Policlinico San Matteo Foundation, Medical Oncology, Pavia, Italy; 7 Department of Electronics, Information and Bioengineering, Politecnico di Milano , and CNAO National Center for Oncological