Uridine phosphorylase is a reliable molecular marker to predict the response of cancer, e.g., squamous cell carcinoma, to treatment with a chemotherapeutic agent or radiation therapy or concomitant treatment with both. Surprisingly, this molecular marker by itself is more accurate than other well-known molecular markers for the prediction of the concomitant chemoradiation response. This marker may be used as a prognostic factor on several types of cancers, including head and neck cancer, skin cancer, ovarian cancer, lung cancer, colon cancer, esophageal cancer, melanoma, and adenocarcinoma. The expression profile of eleven genes may be used to predict the response of cancer cells to chemoradiation therapy.