Anaplastic Thyroid Cancer (Undifferentiated Thyroid Cancer): How Is It Treated? (As of 2026)

Anaplastic (undifferentiated) thyroid cancer progresses extremely rapidly, so it is typically managed by quickly combining surgery, radiation therapy, and drug therapy — a type of thyroid cancer with an entirely different course from papillary or follicular thyroid cancer.

Key Summary

• Anaplastic (undifferentiated) thyroid cancer is a subtype that progresses very rapidly, unlike papillary or follicular thyroid cancer, and is treated with a rapid combination of surgery, radiation therapy, and drug therapy (National Cancer Center Korea).
• Korea's 5-year relative survival rate for thyroid cancer overall is 100.2% (National Cancer Registration Statistics 2019-2023), but this figure reflects outcomes dominated by papillary and follicular cancers and cannot be applied to anaplastic cancer.
• Like medullary thyroid cancer, anaplastic thyroid cancer must be considered separately from the typical thyroid cancer treatment pathway, as it is not a candidate for radioactive iodine therapy.
• If specific genetic alterations are identified, targeted therapy may be considered, and particle therapy may be reviewed as an option in special situations requiring radiation therapy (Thyroid Cancer & Radiation Therapy Note).
• Survival rates are population averages and do not predict individual outcomes; actual treatment decisions should be made in consultation with your medical team.

How Is Anaplastic Thyroid Cancer Different From Other Thyroid Cancers?

• Anaplastic thyroid cancer is the fastest-progressing histologic type among thyroid cancers, with a course entirely different from papillary and follicular cancer, which make up the majority of thyroid cancer cases.
• Korea's combined 5-year relative survival rate of 100.2% for all thyroid cancers (National Cancer Registration Statistics 2019-2023) mostly reflects the favorable outcomes of papillary and follicular cancer, so this figure should not be directly applied to anaplastic cancer patients.
• For this reason, anaplastic cancer is treated separately from the usual thyroid cancer risk classification (low, intermediate, high risk) and standard surgical extent discussions, with the focus instead on rapid multidisciplinary response matched to the pace of disease progression.

What Is the Treatment Sequence?

• Step 1: Because progression is extremely rapid, a plan combining surgery, radiation therapy, and drug therapy is established as quickly as possible.
• Step 2: Radioactive iodine therapy does not apply to anaplastic cancer. Like medullary cancer cells, anaplastic cancer cells lack the ability to absorb iodine, so surgery and drug therapy (including targeted therapy) form the core of treatment from the outset.
• Step 3: When radiation therapy is needed, standard external beam radiation therapy using a linear accelerator is the reference approach. Particle therapies such as carbon-ion or proton therapy are not standard treatment for thyroid cancer, but in special situations like anaplastic cancer, they may be considered as one radiation therapy option.
• Step 4: If specific genetic alterations (RET, NTRK, BRAF, etc.) are identified, corresponding targeted therapy drugs are considered. Targeted therapy is a drug treatment that targets specific proteins or genetic mutations that cancer cells use to grow, and drugs are never selected without test results confirming the relevant mutation.

How Do Standard Radiation Therapy and Targeted Therapy Differ?

• Radiation therapy damages the DNA of cancer cells using high-energy radiation to stop their growth, with external beam radiation therapy delivered from outside the body via a linear accelerator being the most widely used method. No radiation remains in the body after treatment ends, so there is no issue with contact with family members.
• Targeted therapy selects drugs based on genetic alterations or proteins identified in tissue or blood samples, and is not an option if the relevant mutation is absent. Compared to cytotoxic chemotherapy, side effects differ in nature — hair loss and severe nausea are relatively less common, but each drug has its own characteristic reactions (skin rash, diarrhea, blood pressure changes, etc.) that require regular monitoring.
• A distinguishing feature of anaplastic cancer treatment is the rapid combination of these two treatments together with surgery; the order and emphasis of this combination are determined by the medical team based on the pace of disease progression and the patient's overall condition.

FAQ — Do Anaplastic Cancer Patients Also Take Hormone Medication for Life After Surgery?

For typical thyroid cancer, taking thyroid hormone medication for life is standard after total thyroidectomy. Since surgery is often part of anaplastic cancer treatment as well, the same principle may apply depending on the extent of surgery. However, because of the rapid progression of this cancer, the schedule for radiation and drug therapy must be considered together, so the hormone management plan should also be determined jointly with the medical team.

FAQ — Can Anaplastic Cancer Be Treated With Carbon-Ion or Proton Therapy?

Carbon-ion and proton therapy are not standard treatments for thyroid cancer. However, in special, rapidly progressing situations such as anaplastic cancer, they may be considered as one radiation therapy option, and whether they are applicable depends on the tumor's location, stage, and prior treatment history.

Sources and Notes

• This article was written based on the Thyroid Cancer, Radiation Therapy, and Targeted Therapy Notes (National Cancer Center Korea, National Cancer Center, National Cancer Registration Statistics 2019-2023, NCCN Patient Guidelines).
• This content is intended for general medical information purposes only. Diagnosis, treatment methods, and outcomes may vary depending on individual condition. Accurate diagnosis and treatment should always be determined through consultation with your medical team.