As founding member of Southwest Oncology Group and medical oncologist with Central Care Cancer Center in Salina, Kansas, Dr. Mark Fesen draws on more than 25 years of medical experience. After completing his internship and residency in internal medicine at Roger Williams General Hospital in 1990, he went on to complete a medical oncology fellowship at the National Cancer Institute. Board certified in both internal medicine and medical oncology by 1993, Dr. Mark Fesen joined Hutchinson Clinic as a practitioner that same year.

Dr. Mark Fesen served Hutchinson Clinic for nearly two decades, during which time he rose to become senior member of the department of oncology. He also served three years on the clinic's Integrated Health Care Committee and two years as secretary and treasurer of its board of directors. In 2009 he released a book entitled Surviving the Cancer System: An Empowering Guide to Taking Control of Your Care, which earned a feature mention in a US News and World Report article later that year.

An experienced educator as well, Dr. Mark Fesen has served as an assistant clinical professor at the University of Kansas School of Medicine and now serves in the same role at Rocky Vista University. He stands out as contributor to more than 15 peer-reviewed articles, including two with more than 300 citations, and has earned fellowship status in the American College of Physicians.