S495
Clinical - Gynaecological
ESTRO 2026
institutional validation. Strategy of spatial dose summation is crucial for further safety and accuracy of this approach. Keywords: Cervix, Deformable image registration(DIR), IGABT Digital Poster 5146 Impact of Stereotactic Radiotherapy on Disease Control and Survival After Oligoprogression during PARPi in ovarian cancer:A Correlative Analysis Donatella Russo 1 , Bianca Santo 1 , Maria Cristina Barba 1 , Elisa Cavalera 1 , Elisa Ciurlia 1 , Paola De Franco 1 , Sara De Matteis 1 , Giuseppe Di Paola 1 , Angela Leone 1 , Antonella Papaleo 1 , Graziana Ronzino 2 , Angela Sardaro 1 1 Radiotherapy, Vito Fazzi Hospital, Lecce, Italy. 2 Oncology, Vito Fazzi Hospital, Lecce, Italy Purpose/Objective: Poly (ADP-ribose) polymerase inhibitors (PARP-i) have significantly improved outcomes in ovarian cancer, providing disese control in many patients. Oligoprogressive or oligometastatic diseas during PARP-i maintenance represents a clinical problem. Stereotactic radiation therapy (SRT) is a focal approach that can delay the progression of disease and the switch to a new systemic therapy. This study aims to evaluate the relationship between progression-free survival (PFS1 and PFS2) before and after stereotactic radiotherapy (SRT) and overall survival (OS). Material/Methods: Our retrospective analysis investigated patients with oligoprogressive ovarian cancer during PARP-i maintenance. The progression survival from PARP-i initiation to oligoprogression (PFS1), from SRT to subsequent recurrence (PFS2) and overall survival (OS) from the start of PARP-i were all analysed and correlated using Spearman's rank correlation coefficients ( ρ ). The threshold for statistical significance was set
at p < 0.05. A correlation heatmap was used to illustrate the link between the three variables (Figure 1).
Results: Between November 2021 and May 2024, 11 patients with ovarian cancer on PARP-i maintenance therapy underwent stereotactic radiosurgery (SRT) on one to three oligoprogressive sites. A total of 17 lesions were treated.A strong, monotonic relationship was found between PFS2 and OS, indicating that a longer period of post- SRT control was associated with a longer survival time.PFS1 is moderately correlated with both OS and PFS2. This suggests that patients who experienced a longer benefit from PARP-i also tended to benefit for a longer time from SRT.The correlation matrix showed recurring patterns throughout the sample, highlighting the possible predictive interaction between survival outcomes, local control, and systemic treatment duration. Conclusion: The durability of response to PARP-i (PFS1) may predict the subsequent benefit from SRT, supporting the idea that SRT improves disease control in oligoprogression during PARP-i mainteinance.The clinical justification for incorporating SRT into the treatment sequence for patients with limited progression is supported by the strong correlation between PFS2 and OS.These results are hypothesis-generating and require prospective validation in a larger patient group to determine the optimal
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