First results of the NOGGO PERCEPTION: Phase II investigational study of pembrolizumab in combination with chemotherapy in platinum-sensitive recurrent low-grade serous ovarian cancer.

e17548 Background: Low-grade serous ovarian cancer (LGSOC), a rare ovarian malignancy, exhibits a very limited responsiveness to chemotherapy. There is a pressing need for new therapeutic combinations with modern agents to enhance response rates and prognosis in this patient subgroup. Immune checkpoint inhibitors offer a promising pathway, having shown effectiveness in various malignant diseases, including selected cases of ovarian cancer. If our trial should show pembrolizumab effectivity in LGSOC, it would be a signal and impulse for future clinical studies in this rare disease. Methods: This multi-center, single-arm phase II study evaluates pembrolizumab in combination with platinum-based chemotherapy (carboplatin plus pegylated liposomal doxorubicin [PLD] or carboplatin plus gemcitabine) and as maintenance therapy in recurrent LGSOC. Eligible patients include those with disease progression or recurrence ≥6 months post prior platinum-based therapy and ECOG performance status 0-1. The primary endpoint is the 12-month progression-free survival (PFS) rate. Secondary endpoints include overall survival (OS), response rate (RR), PFS and RR based on Ki67 expression, time to first subsequent therapy and response, safety, and quality of life (QoL). Using Simon’s two-stage design, up to 33 patients will be enrolled. The null hypothesis is a 12-month PFS rate of 20%. In stage 1, 18 patients were enrolled, and since 5 achieved the primary endpoint, the study advanced to stage 2, enrolling 15 additional patients. Success is defined as ≥11 patients achieving 12-month PFS. Assuming a true PFS rate of 40%, the study has 5% type I error and 80% power. Results: Data from 18 patients enrolled at interim analysis were evaluated. Of these, 5 patients met the primary endpoint, while 6 patients progressed or died before achieving 12-month PFS. Ten patients remain on treatment, and 7 may still achieve the endpoint. Median patient age was 60 years (range: 43-81), with ECOG 0 in 16 patients (88.9%). Most patients had one prior chemotherapy line (61.1%; range: 1-5). Chemotherapy regimens included carboplatin + PLD (77.8%) and carboplatin + gemcitabine (22.2%). SAEs were reported in 10 patients (55.6%), with 3 (16.7%) deemed treatment-related. One SAE resulted in death but was not related to study treatment. Conclusions: Interim analysis supports the hypothesis that pembrolizumab, in combination with chemotherapy, may extends PFS in recurrent LGSOC. These promising results warrant further investigation in this rare patient population. Clinical trial information: 2023-508155-40-00 .