ESTRO 2024 - Abstract Book

S1019

Clinical - Gynaecology

ESTRO 2024

Poly(ADP-ribose)polymerase inhibitors (PARPi) have an important role among antineoplastic agents, particularly in the treatment of high-grade epithelial ovarian cancer. Neverthless, a considerable number of patients experience relapse or progression under PARPi, requiring the administration of new systemic therapies. Instead of starting a new line of chemotherapy, patients with limited site progression (referred to as an oligometastatic progression) could be considered for local therapy followed by continuation of PARPi treatment.

In this setting the efficacy and safety of stereotactic body radiation therapy (SBRT) has been shown in patients with metastatic, persistent, and recurrent disease.

The aim of this study is to evaluate the efficacy of combination of SBRT treatment and PARPi continuation in patients with oligometastatic progression for recurrent ovarian cancer.

Material/Methods:

This retrospective multicentre study consider patients who were treated between August 2014 and December 2022 with SBRT for oligorecurrent/oligoprogressive disease in ovarian cancer during PARPi systemic therapy. PARPi treatment was continued until further progression of the disease. Data were retrospectively collected and analyzed. Univariate and multivariate analyses were performed to evaluate potential predictive factors for clinical outcomes. The Primary endpoint of the study was prolongation of the PARPi treatment time after local treatment.

Results:

A cohort of 46 patients with 89 treated lesions in 63 SBRT courses, were included. 47.8% of patients were BRCA1 mutated and 67.3% had received more than three prior lines of systemic chemotherapy before locoregional radiotherapy treatment. Lymph nodes were found to be the most frequent treated lesion (89.9%), followed by visceral lesions (9%) and a single case with a bone lesion (1.1%). The median follow-up was 25.9 months (range 2.8– 122 months). A median prolongation of PARPi therapy of 12.4 months (95% CI 8.3-19.5) was observed. More than five lines of systemic therapy prior to SBRT (HR 3.2142, p=0.0316) are correlated with an increased risk of non-oligometastatic progression requiring discontinuation of the PARP inhibitor and treatment change. At the time of analysis, 32 patients were referred to a new systemic therapy regimen (69.6%), while 14 (30.4%) could maintain the ongoing PARPi regimen. The 2 years progression free survival, local failure free survival and overall survival rates were 10.7%, 59.9% and 76.5%, respectively.

In 42 patients (91%) no acute or late toxicities were observed. Four patients experienced acute toxicity with G1 gastrointestinal events.

Conclusion:

This study reports the feasibility and potential benefit of this combinated strategy in patients with oligometastatic progression under PARPi. Further studies with wider populations are needed to better address the potential role of concurrent PARPi in SBRT treatments.

Keywords: ovarian cancer, PARP inhibitors, SBRT