Rochester, Minnesota


Halfdanarson.Thorvardur@mayo.edu Clinical Profile


Thor R. Halfdanarson, M.D., is a medical oncologist at Mayo Clinic who also researches various types of cancer, including pancreatic cancer and neuroendocrine tumors. His specific research interests include the epidemiology, risk factors and treatment of neuroendocrine tumors and improving outcomes for pancreatic adenocarcinoma and rare types of pancreatic tumors. He is a principal investigator and co-investigator for multiple industry-sponsored and cooperative group clinical trials.

Dr. Halfdanarson holds several leadership positions within Mayo Clinic Comprehensive Cancer Center. He is chair of the Hepato-Pancreatico-Biliary Cancer Disease Group and co-chair of the Pancreatic eTumor Board. He is associate medical director of the Cancer Clinical Trials Office in Rochester, Minnesota, co-chair of the Feasibility Committee, and a member of the Clinical Research Leadership Committee. He also represents Mayo Clinic on the Neuroendocrine Tumors Guidelines Panel of the National Comprehensive Cancer Network (NCCN).

Focus areas

  • Epidemiology, incidence, risk factors and prognosis of neuroendocrine tumors, especially pancreatic neuroendocrine tumors.
  • Improved diagnostic methods of neuroendocrine tumors, including nuclear medicine imaging and novel tumor markers.
  • Theragnostics to combine diagnostics and therapeutics, especially using radioligands for diagnosis and management of neuroendocrine tumors. This includes targeting the somatostatin receptor with both alpha particle and beta particle emitters and combination therapy with radioligands.
  • Improving long-term outcomes for locally advanced and borderline resectable pancreatic adenocarcinoma using neoadjuvant therapy.
  • Precision oncology for cancer of unknown primary location and rare tumor types, including rare skin cancers such as extramammary Paget's disease and Merkel cell carcinoma.

Significance to patient care

Through his research, Dr. Halfdanarson seeks to advance treatment options for neuroendocrine tumors. There is an increasing need for long-term therapy and better treatment options through clinical trials. Dr. Halfdanarson hopes to improve options by using novel combinations of systemic therapy and radioligand therapy, along with precision oncology targeting actionable genomics changes.

Professional highlights

  • North American Neuroendocrine Tumor Society (NANETS)
    • President, October 2023-2024.
    • Vice president, 2022-2023.
  • Chair, Hepato-Pancreatico-Biliary Cancers Disease Group, Mayo Clinic Comprehensive Cancer Center, 2023-present.
  • Co-chair, Neuroendocrine Tumor Group, Alliance for Clinical Trials in Oncology, 2022-present.
  • Member representing Mayo Clinic, Neuroendocrine Tumors Guidelines Panel, National Comprehensive Cancer Network (NCCN), 2014-present.


Primary Appointment

  1. Consultant, Division of Medical Oncology, Department of Oncology

Academic Rank

  1. Professor of Oncology
  2. Associate Professor of Medicine


  1. Fellow Department of Hematology and Medical Oncology, Mayo School of Graduate Medical Education, Mayo Clinic College of Medicine
  2. Resident Hematology/Oncology, Programs in Rochester, Mayo School of Graduate Medical Education, Mayo Clinic College of Medicine
  3. Resident Department of Internal Medicine, University of Iowa Hospitals and Clinics
  4. Chief Resident Department of Pediatrics, Reykjavik Hospital
  5. Chief Resident Department of Internal Medicine, Reykjavik Hospital
  6. Resident Department of Internal Medicine, Reykjavik Hospital
  7. Resident Department of Neurology and Rehabilitation, Reykjavik Hospital
  8. Resident Department of Pediatrics, Reykjavik Hospital
  9. Internship - Rotating Internship (Internal Medicine, Surgery, Psychiatry and Emergency Medicine) Reykjavik Hospital
  10. MD Faculty of Medicine, University of Iceland
  11. Physics Menntaskolinn Reykjavik (Reykjavik College)

Clinical Studies

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