Provided are methods for screening a subject for cancer. The methods involve obtaining a blood sample from the subject and determining a level of Bridging Integrator 1 (BIN1) isoforms comprising exon 12a in the sample. Optionally, the method involves determining a level of 12a+/13− BIN isoform (comprising exon 12a but lacking exon 13) in the sample. An elevated level of 12a+(e.g., 12a+/13−) BIN1 isoforms in the blood sample indicates the subject has cancer. Also provided are methods for determining efficacy of a cancer therapy in a subject and methods of treating cancer. Isolated antibodies that selectively bind human 12a+ BIN1 are also provided as well as kits for determining 12a+/13− BIN1 isoforms.