Dr. Cahill is Professor in Neurosurgery at Harvard Medical School, the Vice Chair for Research for the Department of Neurosurgery at Massachusetts General Hospital, and holds the MGH Tawingo Endowed Research Chair.  He is the surgical director of the MGH Brain Metastasis Clinic.

As a neurosurgeon-scientist, his clinical practice is highly-focused on the care of brain tumor patients, and improving national clinical trials of therapy for these patients. His laboratory has received peer-reviewed R01 funding from the National Institutes of Health (NINDS and NCI) and Brain Cancer SPORE grants.  To facilitate precision medicine approaches for diverse CNS tumors, he has collaborated with Dr. Priscilla Brastianos in a systematic effort to characterize the molecular genetic alterations within multiple tumor types.