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e17550 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 clinical trial is a multi-center, single-arm phase 2 study to evaluate pembrolizumab therapy concomitant to platinum-based chemotherapy (carboplatin plus pegylated liposomal doxorubicin & carboplatin plus gemcitabine) and as maintenance in recurrent LGSOC cases. Eligible for the trial are LGSOC patients with progression or recurrence at least six months after most previous platinum-containing therapy and in good general performance (ECOG 0/1). The primary objective is the 12 months progression free survival (PFS) rate. Secondary end-points include overall survival, response rate (RR), PFS and RR according to Ki67 expression levels, time to first subsequent therapy and its response, safety and quality of life. The trial is planned according to Simon’s two-stage design with total sample size up to 33 patients. The null hypothesis is PFS-rate of at least 12 months of 20%. During the first stage 18 patients were enrolled and since 5 patients showed PFS of 12 months the study has been continued within stage 2 to enrol additional 15 patients. The trial can be claimed as successful, if at least 11 patients show PFS after 12 months. Assuming a true PFS-rate of 40%, this trial has 5% type I error rate and 80% power. Results: Data from 18 patients enrolled into this trial from FPI up to the time of interim analysis have been analyzed. 5 patients had reached the primary endpoint. 6 patients progressed or died before they reached the primary endpoint. At this time, 10 patients are still undergoing treatment and 7 patients may still reach the primary endpoint. Patients have a median age of 60 years (range: 43-81), ECOG score of 0 was recorded in 16 patients (88.9%) and most received one prior line of chemotherapy (61.1%, range: 1-5). 14 patients (77.8%) received carboplatin + PLD and 4 patients (22.2%) received carboplatin + gemcitabine as chemotherapy. 10 patients (55.6%) had at least one SAE. 3 patients (16.7%) had at least one SAE with relation to study treatment. 1 SAE resulted in a fatal outcome but was assessed not be related to study treatment. Conclusions: The interim analysis showed positive results, strengthening the hypothesis that pembrolizumab is an effective agent capable of extending progression-free survival in the studied patient population. Clinical trial information: NCT04575961 .
Grabowski et al. (Sat,) studied this question.