Thyroid Cancer

Thyroid Cancer

What is Thyroid Cancer?

Thyroid cancer is likely the most common condition that we treat. Each year, about 45,000 Americans are diagnosed with thyroid cancer. Fortunately, because most thyroid cancers are slow growing, most patients with thyroid cancer do very well and live long, healthy lives with appropriate treatment. Surgery is the mainstay and first treatment for almost all types of thyroid cancer. A minority of patients (about 25%) require radioactive iodine, and beyond that <5% of patients go on to need chemotherapy and/or beam radiation. Below is an overview of the different kinds of thyroid cancer, ranging from the last aggressive to the most aggressive.

There are multiple types of thyroid cancer:

• papillary thyroid cancer
• follicular thyroid cancer
• medullary thyroid cancer
• poorly differentiated thyroid cancer
• anaplastic thyroid cancer

Types of Thyroid Cancer

Papillary Thyroid Cancer

Papillary thyroid cancer makes up about 90% of all thyroid cancers and is carries the best prognosis, with 99% of patients surviving more than 5 years. Indeed, 94% of our patients who are diagnosed with papillary thyroid cancer are disease-free one year after treatment. Papillary thyroid cancer can often be treated with thyroid lobectomy for tumors <4 cm in diameter that have not spread beyond the thyroid to adjacent organs or lymph nodes. Larger tumors and those that show signs of spreading on ultrasound are treated with total thyroidectomy (sometimes with lymph node dissection), followed by radioactive iodine ablation. Survival remains excellent for these patients. Even patients with papillary thyroid cancer that has spread outside the neck (usually to the lungs) enjoy a 5-year survival rate of 74%. Because papillary thyroid cancers are often well-differentiated (meaning, they bear a strong resemblance to the tissue of origin), most papillary thyroid cancers are susceptible to treatment with radioactive iodine. The past decade has seen major technological gains in the treatment of advanced thyroid cancers, and our multidisciplinary team uses every available tool to keep our thyroid cancer patients alive and healthy for years.

Since 2006, researchers across the globe have called attention to the overdiagnosis and overtreatment of small papillary thyroid cancers (<1 cm in diameter). Though this may sound strange, most small papillary thyroid cancers (sometimes called papillary thyroid microcarcinomas or PTMCs) are so small and so slow growing that they do not need treatment. The incidental discovery of small papillary thyroid cancers on screening ultrasounds or imaging tests performed for other reasons led to a rapid rise in the incidence of these cancers in many developed nations, most notably South Korea. Most of these cancers would not have caused any human suffering or death had they been left alone. In fact somewhere between 10 and 30% of people who die from old age are found to have small papillary thyroid cancers on autopsy. For these reasons, active surveillance (monitoring) of small papillary thyroid cancers is gaining acceptance, especially for older people, those with other serious health conditions that would make surgery risky, and patients who are battling other, generally more aggressive types of cancer elsewhere in the body. Patients considering active surveillance must be carefully selected by experienced thyroid doctors and carefully monitored for cancer growth.

Follicular Thyroid Cancer

Follicular thyroid cancer is the second most common type of thyroid cancer, making up about 5% of cases. It also carries a good prognosis, with 5-year survival rates being very similar to those associated with papillary thyroid cancer. Follicular thyroid cancer may be minimally invasive or widely invasive. Minimally invasive cases barely penetrate the tumor capsule and are almost always cured by surgery. Widely invasive follicular thyroid cancers penetrate fully through the tumor capsule and may invade blood vessels (angioinvasion). Cancers with blood vessel invasion are more likely to spread via the bloodstream to distant sites, such as the lungs and bone. Follicular thyroid cancers are often well-differentiated and thus are susceptible to treatment with radioactive iodine.

Differentiated High-grade Thyroid Cancer and Poorly Differentiated Thyroid Cancer

These thyroid cancers are aggressive subtypes of thyroid cancer that are slightly less dangerous than anaplastic thyroid cancer.  Differentiated high-grade thyroid cancer bears some slight resemblance to normal thyroid tissue, whereas poorly differentiated thyroid cancer has lost most of its resemblance to normal thyroid tissue, and can exhibit solid, trabecular, and insular growth patterns.  The 10-year survival rate for these cancers is around 50%.  These are widely invasive tumors that can exhibit necrosis.  Necrosis (areas of dead cancer cells within a tumor) is often a bad sign in cancers, as it indicates rapid tumor growth that outpaces the ability of the blood supply to keep up with the demands of the tumor.

Medullary Thyroid Cancer

Medullary thyroid cancer is rare, comprising about 2% of all thyroid cancer cases. The prognosis for medullary thyroid cancer is slightly worse than that of papillary and follicular thyroid cancer. The 5-year survival rate in localized or regional medullary thyroid cancer is >90%. The 5-year survival rate for medullary thyroid cancer that has spread to distant sites (most often the liver) is 43%. One-fourth of medullary thyroid cancers are hereditary (meaning, they run in families and can be passed on from parent to child) due to activating germline mutations in the RET proto-oncogene. For this reason, genetic counseling is recommended to all patients who are found to have medullary thyroid cancer. Patients with advanced medullary thyroid cancer have benefitted greatly from the recent advent of precision drugs targeting the RET proto-oncogene, such as sorafenib, Lenvatinib, vandetanib, cabozantinib, and more recently selpercatinib and pralsetinib.

Oncocytic Thyroid Cancer

In 2022, Hürthle cell thyroid cancer was renamed oncocytic thyroid cancer. Oncocytic thyroid cancer cells have a characteristic microscopic appearance because they accumulate dysfunctional mitochondria within their cytoplasm. These are rare cancers comprising about 2% of all thyroid cancer cases. The 5-year overall survival rate for oncocytic thyroid cancer is about 85%. Oncocytic thyroid cancer may be minimally invasive or widely invasive. Minimally invasive cases barely penetrate the tumor capsule and are almost always cured by surgery. Widely invasive oncocytic thyroid cancers penetrate fully through the tumor capsule and may invade blood vessels (angioinvasion). Cancers with blood vessel invasion are more likely to spread via the bloodstream to distant sites, such as the lungs and bone. Up to 25% of oncocytic thyroid cancers recur, with the risk of recurrence being strongly linked to the degree of invasion, especially angioinvasion. Recurrent oncocytic thyroid cancer is difficult to treat, owing partially to the fact that 95% of these tumors do not respond to radioactive iodine. However, the unique genetic characteristics of oncocytic thyroid cancers may make them more susceptible to external beam radiation therapy.

Anaplastic Thyroid Cancer

Anaplastic thyroid cancer is extremely rare and considered the most dangerous form of thyroid cancer. Anaplastic thyroid cancer occurs in older people: the average age at diagnosis is 65 years, with 90% of patients being over age 50. Historically, anaplastic thyroid cancer has been associated with very poor survival – typically just a few months, with less than 20% of patients surviving more than one year. However, since 2018 we have seen a revolution in the treatment anaplastic thyroid cancer, offering many patients hope for what was up until recently a uniformly fatal diagnosis. Up to 40% of anaplastic thyroid cancers harbor the BRAF V600E mutation. These patients are eligible for combination treatment with the new targeted agents dabrafenib and trametinib (BRAF plus MEK inhibitor). For patients whose tumors are advanced beyond the point where surgery is possible, up-front (neoadjuvant) treatment with dabrafenib/trametinib may downstage (shrink) the tumor to the point that surgery once again becomes an option. New research on anaplastic thyroid cancer in the era of these advanced treatments is promising, with some studies showing a 2-year survival as high as 50%. A small number of these patients are showing long-term remission.

If you are found to have anaplastic thyroid cancer on a biopsy, it is essential that you seek care immediately at a major cancer center for BRAF testing.  Major cancers can be found through the National Comprehensive Cancer Network (NCCN).  NCCN is a not-for-profit alliance of 33 leading cancer centers devoted to patient care, research, and education. NCCN is dedicated to improving and facilitating quality, effective, equitable, and accessible cancer care so all patients can live better lives.

Thyroid Cancer Treatment

Thyroid cancer treatment is very successful. About 95% of thyroid cancer patients live more than five years, and most thyroid cancer patients experience a normal life span and full quality of life after appropriate treatment.  Even patients with advanced thyroid cancer may often do well with modern targeted therapies. The key components of thyroid cancer treatment for most types of thyroid cancer are surgery, thyroid stimulating hormone suppression, and ongoing surveillance of tumor markers with dynamic risk stratification. Patients with a high risk of disease recurrence may also be offered radiation therapy with radioactive iodine. Newer targeted therapies and immunotherapy may be used for patients with advanced and metastatic disease outside of the neck.

Key Components of Differentiated* Thyroid Cancer Management

• Thyroid Surgery
• Thyroid stimulating hormone suppression
• Radioactive iodine ablation (in some patients)
• Dynamic Risk Stratification informed by ongoing surveillance with tumor markers and imaging

* Differentiated thyroid cancer includes Papillary, Follicular, and Hurthle cell thyroid cancer. Treatment for poorly differentiated, anaplastic, and medullary thyroid cancers are distinct and discussed separately.

Special Populations with Thyroid Cancer

Dr Harvey Chiu at UCLA

As a referral center for difficult cases, we also have experience in treating patients with special circumstances.

Genetic Syndromes

We are also part of specialized teams that care for patients and their families with:

• Multiple Endocrine Neoplasia (MEN-1, MEN-2A, MEN-2B, MEN4)
• Familial pheochromocytoma
• Von-Hippel-Lindau

Appointments

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