Development and Validation of an Oral Cavity Cancer Outcomes Prediction Score Incorporating Patient-Derived Xenograft Engraftment

Patient-derived xenografts (PDXs) offer the opportunity to identify patients with oral cavity squamous cell carcinoma (OSCC) who are at risk for recurrence and optimize clinical decision-making.To develop and validate a prediction score for locoregional failure (LRF) and distant metastases (DM) in OSCC that incorporates PDX engraftment in addition to known clinicopathological risk factors.In this retrospective cohort study, PDX models were generated from patients with OSCC treated with curative intent at Princess Margaret Cancer Centre (Toronto, Canada) between 2006 and 2018. The cohort included 288 patients (aged ≥18 years) with a new diagnosis of nonmetastatic (M0) OSCC whose tumor samples were available for engraftment under the skin of xenograft mice. Patients were scored as a nonengrafter if PDX formation did not occur within 6 months. Data analysis was performed between August 2006 and May 2018.All patients received up-front curative-intent surgery followed by either observation or postoperative radiation with or without concurrent chemotherapy based on institutional guidelines.Main outcomes were LRF, DM, and overall survival (OS). Multivariable analysis (MVA) was used to identify predictors of LRF and DM. Factors retained in the final MVA were used to construct a prediction score and classify patients into risk groups.Overall, 288 patients (mean [SD] age at diagnosis, 63.3 [12.3] years; 112 [39%] women and 176 [61%] men) with OSCC were analyzed. The MVA identified pT3-4, pathologic extranodal extension, and engraftment as predictors of LRF and DM. Patients whose tumors engrafted (n = 198) were more likely to develop LRF (hazard ratio [HR], 1.98; 95% CI, 1.24-3.18) and DM (HR, 2.64; 95% CI, 1.21-5.75) compared with nonengrafters. A prediction score based on the aforementioned variables identified patients at high risk and low risk for LRF (43.5% vs 26.5%), DM (38.2% vs 8.4%), and inferior OS (34% vs 66%) at 5 years. Additionally, rapid engraftment was shown to be similarly prognostic, with rapid engrafters demonstrating higher rates of relapse and poor OS.In this cohort study, a prediction score using OSCC PDX engraftment, in conjunction with pT3-4 and pathologic extranodal extension, was associated with improved prognostic utility of existing clinical models and predicted patients at risk for LRF, DM, and poor survival.