Introduction PARP inhibitors (PARPi) have changed the management landscape for patients with epithelial ovarian cancer (EOC). However, as with many targeted therapies, treatment resistance is common. The response to treatment post-PARPi has not been well described in trials. Data is needed to better understand disease course, and guide treatment decisions. The primary aim is to describe the treatment patterns post-PARPi. Secondary aims are to describe patient characteristics who received chemotherapy post-PARPi and DoR to chemotherapy.Methods Retrospective analysis of women with EOC treated with PARPi either in the maintenance or treatment setting and via government-funded or clinical trial access at six gynaecological oncology centres. Between 2007–2019 eligible women were identified via clinics, trial databases and pharmacy dispensing logs. Information regarding clinico-pathological characteristics and treatment outcomes were collated from medical records.Results Eighty-five women with EOC were identified. 90.6% received chemotherapy post-PARPi, with 72.7% receiving platinum-based chemotherapy. Clinicopathological characteristics in table 1.Best responses observed were 5.2% CR, 19.5% PR, 19.5% SD, and 55.8% PD. Median DOR was 7.0 months (range, 0.2 – 20.4 months) in 77 patients receiving chemotherapy post-PARPi. Eight patients did not receive further systemic therapy due to poor performance status. Women who received platinum doublet chemotherapy post-PARPi had a longer mPFS than those receiving platinum single agent or non-platinum chemotherapy (9.1 months vs 3.3 months vs 5.0 months, respectively p=0.0004).View this table:Abstract 402 Table 1 Clinicopathological characteristicsConclusion Most patients received-platinum based chemotherapy post-PARPi with a modest response rate. Potential overlapping mechanisms of resistance to PARPi and platinum require further study to improve patient outcomes.