Dr Hahn sees patients with urothelial cancers, including non-muscle invasive bladder cancer, and provides care to patients with non-urothelial genitourinary malignancies, including prostate, testicular, and other rare tumors. He is the bladder cancer chairman of the Eastern Cooperative Oncology Group, co-chairs the Hoosier Cancer Research Network genitourinary oncology clinical trials working group, is a member of the NCI Bladder Cancer Task Force, and serves on the scientific advisory board of the Bladder Cancer Advocacy Network.