[PROBLEMS] To identify mutations that can serve as indicators for predicting the effectiveness of drug treatments in cancers such as lung cancer to provide a means for detecting said mutations and to provide a means for identifying, based on said mutations, patients with cancer or subjects with a risk of cancer, in which drugs targeting genes having said mutations or proteins encoded by said genes show a therapeutic effect.[MEANS FOR SOLVING] A method for detecting a gene fusion serving as a responsible mutation (driver mutation) for cancer, the method comprising the step of detecting any one of an EZR-ERBB4 fusion polynucleotide, a KIAA1468-RET fusion polynucleotide, a TRIM24-a BRAF fusion polynucleotide, a CD74-NRG1 fusion polynucleotide, and an SLC3A2-NRG1 fusion polynucleotide, or a polypeptide encoded thereby, in an isolated sample from a subject with cancer.
