Burrowing Behavior as Robust Parameter for Early Humane Endpoint Determination in Murine Models for Pancreatic Cancer

Due to late-stage diagnoses and limited treatment options, pancreatic cancer is predicted to be the second leading cause of cancer deaths by 2030. Many different murine models were developed over the past decades to test new therapies for this tumor entity. The laws and regulations demand the continuous refinement of animal experiments in order to improve animal welfare sustainably. A key aspect here is the definition of early humane endpoint criteria to avoid severe and lasting suffering of the animals through timely euthanasia. The present study analyzed the welfare of mice in different pancreatic cancer models, various mouse strains, and under different therapeutic interventions in preclinical testing. Their welfare was monitored before any intervention, during tumor progression, and on the days before the individual humane endpoint for each mouse by assessing body weight change, distress score, perianal temperature, burrowing behavior, nesting activity, and mouse grimace scale. The data was retrospectively analyzed via receiver operating characteristic curve analysis to quantify the predictability of each parameter for humane endpoint determination. Burrowing behavior proved to be a robust predictor of the humane endpoint two days in advance under various conditions, including diverse pancreatic cancer models and different therapeutic approaches.