Optimizing drug sensitivity assays in patient-derived tumor organoids: a comparison of IC50 estimation methods and experimental parameters.

Patient-derived tumor organoids (PDOs) hold immense potential for personalized drug sensitivity testing, but accurate efficacy determination is crucial for clinical translation. This study investigated factors influencing the accuracy and reproducibility of drug sensitivity measurements in PDOs, focusing on half-maximal-inhibitory-concentration (IC50) calculation methods, drug concentration numbers, and plate types. PDOs were established from six primary cancer tissues, including two cervical resections, one lung biopsy, one lung pleural effusion, one breast biopsy, and one gastric resection. They were subjected to drug sensitivity assays with 21 single/combined treatments, encompassing chemotherapy and targeted therapy drugs, with concentrations standardized in fold. Utilizing 6- and 12-concentration setups, IC50 derived from GraphPad-Dose-response-Inhibition (DRI), LC-logit, and LC-probit methods were compared. Relative changes (RCs) in IC50 and area-under-the dose-response-curve (AUC) between setups and the impact of plate type on cell viability measurements were assessed. In the 12-concentration setup, no significant IC50 differences were observed among the calculation methods. Notably, GraphPad-DRI and LC-logit exhibited minimal RCs between the 6- and 12-concentration setups (0.035 and -0.033, respectively), indicating accurate IC50 quantification even with fewer drug concentrations. AUC correlated strongly with GraphPad-DRI-derived IC50 (R = 0.858) and demonstrated lower variance between technical replicates. Furthermore, opaque-bottom plates yielded higher precision in cell viability measurements compared to transparent-bottom plates. This study provides valuable insights into optimizing drug sensitivity testing in PDOs. By demonstrating the robustness of specific IC50 calculation methods and the feasibility of using fewer drug concentrations, this study contributed to the standardization and reliability of PDO-based drug sensitivity assays.