ESTRO 2024 - Abstract Book

S1023

Clinical - Gynaecology

ESTRO 2024

Purpose/Objective:

To present a nationwide survey on the current attitudes of Italian specialists towards stereotactic radiotherapy (SBRT) combined with PARPi in patients with oligometastatic/oligoprogressive/oligorecurrent ovarian cancer (MPR-OC).

Material/Methods:

The survey was developed by ovarian cancer specialists and distributed through networks and organizational partners of the Gynecology Study Group of the Italian Association of Radiation and Clinical Oncology (AIRO GYN) along with the Multicenter Italian Trials in Ovarian Cancer and Gynaecologic Malignancies (MITO). A 20-item questionnaire was distributed online via SurveyMonkey. Outcomes were stratified by categories and analyzed using descriptive statistics.

Results:

One hundred radiation therapy centers completed the survey. Respondents were radiation oncologists (57%), medical oncologists (32%), and gynecologic cancer surgeons (11%). Most respondents work in public or university hospitals (63%) across the Country with no major geographical differences. A tumor board for OC was reported by 89% of participating institutions, including "almost always" a radiation oncologist (100% of cases), a gynecologic cancer surgeon (87% of cases), and a medical oncologist (87% of cases), in half of cases a radiologist (47%) and a pathologist (43%), sometimes a nuclear medicine physicist (16%). The referral specialist for MPR-OC is considered the medical oncologist by 54% of respondents, followed by radiation oncologist (23%) and gynecologic oncologist (15%), however, 74% of the centers in the presence of MPR-OC chose to discuss the case in the multidisciplinary tumor board, while 15%, 6%, and 2% send the patients straight to SBRT, surgery, or chemotherapy, respectively. In 2022, 74% centres treated fewer than 10 MPR-OC patients, 13% treated between 10 and 25 patients, 6% treated between 26 and 75 patients, and 3% were unable to quantify. According to center responses, <30%, between 30% and 70%, between 70 and 100% of patients, in 27, 31, and 20 centers, respectively, were under treatment with PARPi. 17% of centers were unable to quantify. Seventy percent of respondents believe that the combined administration of PARPi and SBRT has positive effects. However, there is significant variation in how PARPi is managed while SBRT is being administered. Some centers (33%) do not interrupt the administration while others (67%) pause it and restart it at a later time. Patients who receive both PARPi and SBRT had little to no reported side effects. The remaining cases favour always interrupting (9%), only interrupting in certain cases (9%), such as site, target size, or high risk of toxicity, or cannot provide an answer (27%). 43% of respondents believe that the PARPi dosage should not be reduced when administered concurrently with SBRT. The majority (69%) of respondents stated that, if he constraints for organs at risk are met, the SBRT dose should not be reduced when combined with PARPi. The majority of respondents (40%) favoured the use of expert consensus as the most effective approach for enhancing the clinical management of MPR-OC, while others (30%) suggested clinical guidelines. Additionally, the majority (66%) expressed willingness to participate in future studies related to this subject matter.

Conclusion:

The present survey identifies uncertainties regarding the referring specialist and clinical protocols for combining stereotactic radiotherapy with PARPi. Moreover, it emphasizes the low number of patients who have received this treatment approach nationwide. Future national clinical collaborative studies are advocated in order to investigate these controversial topics about MPR-OC.