Stereotactic Body Radiation Therapy for Oligoprogressive Ovarian Cancer Patients Treated During Poly(ADP-Ribose)-Polymerase Inhibitor Maintenance: Efficacy and Adverse Events From the Epimetheo Retrospective Study.

Purpose: The aim of this observational, retrospective, multicenter study (Epimetheo) was to analyze the activity and the safety of stereotactic body radiation therapy (SBRT) during poly(ADP-ribose)-polymerase inhibitor (PARPi) maintenance in a series of oligometastatic ovarian cancer (OC) patients.
Methods and Materials: Patients treated with PARPi in maintenance setting received SBRT if oligometastatic progression occurred. Maintenance treatment was continued until the extensive progression of the disease. The primary endpoints of the study were as follows: next systemic treatment change-free survival (NEST-FS) and acute and late toxicity; the secondary endpoints were as follows: the rate of clinical complete response (CR), the 2-year actuarial local control (LC, progression of disease inside SBRT field) rate on "per lesion" basis, the 2-year actuarial progression-free survival, and 2-year overall survival (OS).
Results: From April 2018 to September 2023, SBRT was used to treat 74 OC patients with a total of 158 lesions (98 lymph nodes and 60 parenchymal lesions) under PARPi maintenance. Olaparib, niraparib, and rucaparib were administered to 41.9%, 48.6%, and 9.5% of patients, respectively. CR, partial response, stable disease, and progressive disease were observed in 115 (72.8%), 32 (20.3%), 9 (5.7%), and 2 lesions (1.3%), respectively. Severe toxicities were reported in less than 3% of patients. The actuarial median NEST-FS was 10 months, with a range of 6.7-13.3 months. The 12- and 24-month actuarial NEST-FS rates were 44.9% and 31.4%, respectively. The 2-year actuarial LC, progression-free survival, and OS were 68.1%, 22.5%, and 77%, respectively with differences in figures between complete and incomplete responders. The achievement of CR was found to be correlated with an improvement in LC and OS.
Conclusions: This study reports the activity and the low toxicity profile of SBRT in association with PARPi in oligometastatic OC patients. A rapid, minimally invasive, and cost-effective treatment such as SBRT may be proposed as a means of prolonging NEST-FS and maintaining an effective treatment regimen involving PARPi.
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