Disclosed are a novel therapeutic agent for cancer such as esophageal squamous cell carcinoma, a method for predicting the prognosis of cancer, and a method for detecting, or predicting the prognosis of, cancer such as esophageal squamous cell carcinoma using a sample that can be collected less invasively. The therapeutic agent for cancer comprises as an effective component an antibody that undergoes antigen-antibody reaction with FGFRL1 to suppress the growth of cancer cells, or an antigen-binding fragment thereof. The method for predicting the prognosis of cancer comprises investigating the expression level of FGFRL1 in a cancer tissue separated from a living body, and, in this method, a high expression level of FGFRL1 indicates poor prognosis. The method for detecting cancer comprises measuring FGFRL1 or a fragment thereof extracted from a body tissue, or FGFRL1 or a fragment thereof in blood separated from a living body, and, in this method, a higher concentration of FGFRL1 or the fragment thereof contained therein than the concentration of FGFRL1 or the fragment thereof in the tissue or blood of a healthy individual indicates the presence of cancer.
