Dr. Shirai earned his medical degree at Kyoto University in Kyoto, Japan. He then completed a transitional internship at the United States Naval Hospital in Yokosuka, Japan, and a residency in Internal Medicine at the Aso Iizuka Hospital in Fukuoka, Japan. He then completed a residency in Radiation Oncology at the Hokkaido Cancer Center of the National Sapporo Hospital in Hokkaido, Japan before relocating to the United States, where he completed a residency in Internal Medicine at the University of Pittsburgh Medical Center in Pittsburgh, Pennsylvania. He completed a fellowship in Internal Medicine at the Medical University of South Carolina in Charleston, South Carolina while also earning a Master of Science degree in Clinical Research.

He is a Professor of Medicine at the Geisel School of Medicine and a medical oncologist at the Dartmouth Cancer Center where he has served as the Director of the Melanoma Collaborative Oncology group. In addition to melanoma, his clinical work focuses on immunotherapy in head and neck and lung cancer. He is a member of the Dartmouth Cancer center and committed to the Cancer Center’s mission to promote clinical trials with sound procedures and methods.