1342 Longitudinal detection of circulating tumour cells in serous and non-serous epithelial ovarian carcinomas

Introduction/Background Metastasis is the primary cause of cancer mortality. The migration of tumour cells known as circulating tumour cells (CTCs) in the bloodstream form part of the 'liquid biopsy'. CTC enumeration serves as prognostic marker in breast, prostate, and colorectal cancers. However, due to technical challenges, its relevance in epithelial ovarian carcinomas (EOC) remains limited. Therefore, we examined CTCs longitudinally in serous and non-serous EOCs. Methodology Peripheral blood samples were collected from 62 patients with EOC at diagnosis (serous: n=48 (47 high-grade,1 low-grade); non-serous: n=14 (6 clear-cell, 4 endometroid, 1 mucinous, 3 mixed)). A subset underwent primary-cytoreductive surgery (PCRS) with samples collected 2-days post-op (12/32) and from the ovarian vein (19/32). Samples were taken post-chemo for patients receiving neoadjuvant chemotherapy (NACT) (17/30), and at 1-year follow-up or recurrence (22/62). CTCs were enriched using Parsortix® Technology and enumerated DAPI, CK7, panCK, EpCAM+, CD45-. CTC counts were correlated with clinicopathological data. Results CTCs were detected in 56% of patients with EOC at diagnosis (1- 22 CTCs/7.5 mL blood). Those who underwent ovarian vein sampling, 58% had detectable CTCs in the vein sample. Peripheral CTC-positivity rate was 50% 2 days post-PCRS and 41% post-NACT. 62% of samples at 1-year follow-up had CTCs, where 85% of these had recurred. 77% of patients who recurred had CTCs at diagnosis. CTC-positivity had no significant effect on PFS, where median follow-up time was 18 months. No significant differences in CTC counts were observed between serous and non-serous cohorts for sample timepoint, ovarian vein sampling, CA-125 levels (p=0.07), or primary tumour size (p=0.06). CTCs were detected at all sample timepoints in both serous and non-serous EOC. Conclusion CTCs were detected at all timepoints assessed during treatment of EOC. Enumerating CTCs throughout treatment in EOC is imperative to assess their clinical significance. Ongoing follow-up and longitudinal sampling of this patient cohort continues. Disclosures None.