J. Mark Barnett, M.D.


Dr. Barnett is a medical oncologist at Rocky Mountain Cancer Centers in Longmont. He is the chairman of the Cancer Committee at Longmont United Hospital. He is the recipient of the 2010 Medical Staff Service Excellence Award at Longmont United Hospital. Position: Medical Oncologist, Rocky Mountain Cancer Centers.



While Dr. Barnett sees all types of cancer and hematologic disease, he has a special interest in the following areas:

  • Gastrointestinal malignancies
  • Lymphoma and hematologic malignancies
  • Breast cancer


When not seeing patients, Dr. Barnett enjoys cycling, paddle boarding and exploring the west with his wife and three children.

Education & Background

Undergraduate: Bachelor of Arts, University of Illinois, Champaign, Illinois

Medical School: Doctor of Medicine; Southern Illinois University School of Medicine, Springfield, Illinois

Internal Medicine Residency Program: Rhode Island Hospital, Providence, Rhode Island

Hematology and Oncology Fellowship: Brown University School of Medicine, Providence, Rhode Island


Board Certification: American Board of Internal Medicine, board certified in internal medicine, board certified in medical oncology Clinical Research: Focus on clinical trials for patients with breast or gastrointestinal cancer as well as early phase (I and II) clinical trials for patients with solid tumors
Awards: Young Investigator Award, SWOG Career Development Award, American Society of Clinical Oncology – ASP

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