Dr. Thorvardur R. Halfdanarson, M.D.
Medical Oncology (Medical Oncology Physician)
- Medicare participating
At a glance
- Years since graduation
- 31
- In the NPI registry since
- 2006
- Medicare patients seen, 2024
- 440
The NPI date is when this clinician registered for a National Provider Identifier, the billing number used on health claims. It is not a license, graduation or board-certification date. NPIs were first issued in May 2005 and became required on claims in 2007–2008, so an early date usually means the clinician was already in practice before then. What an NPI is
Education and training
- 2006Registered with an NPI (national billing number; not a license date) — NPIs began in 2005, so practice likely started earlier
Medicare’s Care Compare data doesn’t list this clinician’s medical school. Undergraduate school, residency, fellowship, licensing exams and board certification aren’t in public federal data. Board certification can be confirmed with the certifying board (ABMS member boards for MDs, AOA boards for DOs).
Specialties and state licenses
-
Medical Oncology Physician primary
MN license 45995 -
Hematology & Oncology Physician
AZ license 46666 · IA license 37199 · MN license 45995 -
Internal Medicine Physician
IA license 37199 · MN license 45995
As reported to the NPI registry. To confirm a license is current, check the state medical board.
Where they work
Hospitals
- Mayo Clinic Hospital Rochester Rochester, MN
- Mayo Clinic Health System New Prague New Prague, MN
Medical groups
- Mayo Clinic (4,956 clinicians)
Hospitals this clinician lists with Medicare, and groups they bill Medicare through (Care Compare). Affiliation doesn’t mean they see patients at every location.
Medicare patients and services
- Medicare patients, 2024
- 440
- Services billed
- 59,372
- Patients’ average age
- 72
| Service | Times | Patients |
|---|---|---|
| Injection, pembrolizumab, 1 mg | 6,700 | 26 |
| Injection, fosaprepitant, 1 mg | 6,300 | 37 |
| Injection, paclitaxel, 1 mg | 4,752 | 22 |
| Injection, daratumumab, 10 mg and hyaluronidase-fihj | 3,781 | 20 |
| Injection, rituximab-pvvr, biosimilar, (ruxience), 10 mg | 1,210 | 16 |
| Injection, ondansetron hydrochloride, per 1 mg | 1,048 | 81 |
| Injection, dexamethasone sodium phosphate, 1 mg | 954 | 75 |
| Injection, bortezomib, 0.1 mg | 615 | 16 |
| Injection, palonosetron hcl, 25 mcg | 340 | 29 |
| Injection of additional new drug or substance into vein | 244 | 111 |
Medicare fee-for-service only. CMS leaves out services billed for fewer than 11 patients. These figures describe a practice’s Medicare work; they aren’t a measure of quality.
Medicare prescriptions
| Drug | Prescriptions |
|---|---|
| Colestipol Hcl Other prescribers in Rochester, MN | 24 |
| Xermelo (telotristat etiprate) | 16 |
| Eliquis (apixaban) Other prescribers in Rochester, MN | 15 |
| Ondansetron Hcl Other prescribers in Rochester, MN | 14 |
Prescriptions filled under Medicare Part D, including refills. CMS leaves out drugs prescribed fewer than 11 times.
Payments from drug and device companies
In 2025, 6 companies reported 14 payments worth $27,451 in total to this clinician.
| Genzyme Corporation | $16,790 |
|---|---|
| E.r. Squibb & Sons, L.l.c. | $3,719 |
| Exelixis Inc. | $3,588 |
| Boehringer Ingelheim Pharmaceuticals, Inc. | $1,850 |
| Boehringer Ingelheim International GmbH | $1,480 |
| Curium US LLC | $24.82 |
| Travel and Lodging | $12,897 |
|---|---|
| Consulting Fee | $10,854 |
| Honoraria | $3,300 |
| Food and Beverage | $400 |
What the payments were for
| Company | What it was for | Amount |
|---|---|---|
| Genzyme Corporation Oct 16, 2025 | Travel and Lodging travel to Berlin, Germany · in-kind | $8,990 |
| Genzyme Corporation Oct 16, 2025 | Consulting Fee | $7,524 |
| Exelixis Inc. Dec 12, 2025 | Honoraria CABOMETYX · Renal Cell Carcinoma (RCC) Hepatocellular Carcinoma (HCC) Differentiated Thyroid | $3,300 |
| E.r. Squibb & Sons, L.l.c. Mar 5, 2025 | Travel and Lodging travel to Krakow, Poland | $3,280 |
| Boehringer Ingelheim Pharmaceuticals, Inc. Aug 28, 2025 | Consulting Fee | $1,850 |
| Boehringer Ingelheim International GmbH Aug 27, 2025 | Consulting Fee | $1,480 |
| E.r. Squibb & Sons, L.l.c. Mar 4, 2025 | Travel and Lodging travel to Krakow, Poland | $368 |
| Genzyme Corporation Oct 16, 2025 | Travel and Lodging travel to Berlin, Germany · in-kind | $258 |
Each payment as the company reported it, with the products it named. Meals are counted in the totals above but not listed one by one.
From CMS Open Payments. A payment is not evidence of wrongdoing; many are for consulting, teaching or meals. Clinicians can review and dispute their records with CMS.
Industry-funded research
Named as a principal investigator on 7 industry-funded studies in 2025, from 6 companies. The companies reported $1,128,215 in research payments for these studies, mostly to the institutions running them.
- Study of RYZ101 Compared With SOC in Pts w Inoperable SSTR+ Well-differentiated GEP-NET That Has Progressed Following 177Lu-SSA Therapy
E.r. Squibb & Sons, L.l.c. · Active, not recruiting · NCT05477576 - Expanded Access use of IMDELLTRA in a 64-year-old patient who was diagnosed with DLL3+ metastatic, poorly differentiated small cell cancer of the esophagus
Amgen Inc. - Expanded Access use of IMDELLTRA in a 71-year-old patient who was diagnosed with DLL3+ metastatic non-small cell carcinoma with neuroendocrine differentiation
Amgen Inc. - A Phase III Multi-center, Randomized, Open-label Study to Evaluate the Efficacy and Safety of Lutathera in Patients With Grade 2 and Grade 3 Advanced GEP-NET
Novartis Pharmaceuticals Corporation - Phase II study in SCLC and epNEC
Boehringer Ingelheim Pharmaceuticals, Inc. - DAREON-5: An open-label, multi-center Phase II dose selection trial of intravenous BI 764532, a DLL3-targeting T cell engager, in patients with relapsed/refractory extensive-stage small cell lung cancer and in patient…
Boehringer Ingelheim Pharma GmbH & Co.kg - Phase II study in SCLC and epNEC
Boehringer Ingelheim International GmbH
From CMS Open Payments research payments, where companies name up to five principal investigators per payment. Research payments usually go to hospitals, universities and research sites, not to the investigator personally. A payment is not evidence of wrongdoing.