Towards a functional model of drug sensitivity in advanced-stage ovarian cancer: clinical correlation of drug sensitivity assays in organoid tissue cultures

Objectives: Though many ovarian cancer patients respond to primary treatment, a significant portion will not respond and are considered ‘platinum resistant/refractory.’ Such patients experience a significantly worse prognosis relative to those who are ‘platinum sensitive.’ Pre-treatment prediction of platinum sensitivity has eluded scientists, which forces clinicians to undergo a ‘trial and error’ method of treatment by which resistant patients are forced to try and fail a futile line of therapy. Patient-derived organoid (PDO) cultures represent a potentially powerful functional model which preserves tumor heterogeneity (Hill et al, 2018). Here, we describe the successful culture of 4 PDOs from patients with advanced stage ovarian carcinoma and their correlation with clinical treatment outcome. Methods: Fresh tissue was obtained from the patients’ debulking surgery. It was digested, and a cell pellet was created. The pellet was washed several times, re-suspended in Matrigel, plated, and grown at 37oC over several days. PDOs were treated with standard doses of carboplatin (1 µM) and paclitaxel (10 nM). The percent of viable cells at 72 hours was measured using the CellTiter-Glo 3D platform (Promega, Madison, WI). The patients’ clinical charts were then reviewed 6 months after the completion of primary chemotherapy to determine clinical platinum sensitivity as defined by clinical parameters. Results: PDOs were successfully obtained from each of the four patients with advanced stage ovarian carcinoma. Three patients had primary disease, and 1 patient was being treated for a recurrence. The patient with recurrent disease received chemotherapy immediately prior to her debulking surgery, and the rest underwent primary debulking surgery with chemotherapy to follow. Three patients had high grade serous histology, and 1 patient had low grade serous histology. Three patients ultimately had platinum resistant disease, and their PDOs all demonstrated >50% cell viability in response to carboplatin and paclitaxel with 2 resistant PDOs demonstrating a remarkable 90% and 95% cell viability. The PDO from the patient with platinum sensitive disease by clinical criteria demonstrated 49% cell viability in response to treatment (Table 1). Download : Download high-res image (123KB) Download : Download full-size image Conclusions: We describe the successful creation of PDOs from fresh tissue obtained from debulking surgery in advanced stage ovarian cancer patients. If we use ≥50% cell viability as our initial, preliminary sensitivity threshold, results from the PDO drug sensitivity assay correlate with clinical platinum sensitivity in this pilot feasibility. We propose to confirm the predictability of drug sensitivity thresholds in future, larger studies using PDOs. Currently, there is no standardized drug sensitivity assay or response parameters defined as predictable for PDOs. Such work will be integral in the formation of a functional model of drug sensitivity, which can be used in the clinic to predict platinum sensitivity without requiring a patient to try and fail futile treatments.