Post-Chemoradiotherapy Low Anterior Resection Syndrome Prediction Model (PORTLARS) PORTLARS, or the Post-Chemoradiotherapy Low Anterior Resection Syndrome Prediction Model, is a mathematical model designed to help doctors evaluate the risk of severe bowel dysfunction after anterior resction proceded by chemoradiotherapy in rectal cancer patients. Low Anterior Resection Syndrome (LARS) scoring system is used to assess the bowel dysfunction. The interactive PORTLARS tool is easy to use. Simply input 5 clinical variables shown below, and the risk of major LARS would be presented. The PORTLARS tool does not collect or store any individual data.