A Recurrence Study is an extended study during which Certis continues to monitor O-PDX cohorts after an efficacy study is complete. A growing body of evidence shows O-PDX models are not only highly predictive of tumor therapeutic response but can predict drug resistance and tumor recurrence before they become evident in human patients. If leveraged in drug development, this provides an opportunity to inform the development of second-line treatments even as first-line therapies are under development.