Thyroid Cancer
Although the incidence of thyroid cancer is increasing by roughly 4% a year, the mortality of the disease has not changed. The reason for the increase is not clear, but could be due to an increase in the number of ultrasound, MRI, and CT Scans of the neck being done for other reasons. Thus the cancers are being diagnosed at an earlier stage and thus more easily cured. The treatment and cure rate of thyroid cancer is dependent on the type and extent (how big and has it spread to other parts outside of the thyroid gland). At the CENTER we have extensive experience in treating all types of thyroid cancers; each type of cancer has it’s specific characteristic and has to be treated with this in mind.
Types of Thyroid Cancers
The four kinds of thyroid cancer are papillary, follicular, medullary, and anaplastic. Papillary & Follicular are characterized generally as well differentiated (meaning they have more characteristics of the thyroid gland), while anaplastic is at the opposite end of the spectrum with little remaining similarity to the thyroid gland.
Information on Thyroid Cancer:
Papillary Thyroid Carcinoma & Follicular Thyroid Carcinoma
Papillary and Follicular thyroid carcinomas are referred to as well-differentiated thyroid cancer and account for 90% of all thyroid cancers. Both types tend to be relatively slow growing; therefore we, at the CENTER have a great opportunity of curing our patients with the most advanced minimally invasive techniques.
Papillary thyroid carcinomas (PTC) are the most common type of thyroid cancer accounting for 80% of cases. It happens twice as often in women then men, and is most common in the ages of 30′s and 40′s. 85% of cases show more then one tumor in the thyroid gland (termed Multi-focal, Figure 1 & 2). Spread to the local lymph nodes is common, but involvement of the lymph nodes does not seem to affect long-term survival when treated appropriately (removal of the lymph nodes or neck dissection). Spread to other parts of the body (metastasis) such as lung, bones and liver area very rare. Some of the subtypes of papillary include tall cell variant, sclerotic, insular, etc. In general the 20-year survival rate for PTC is greater then 90%. Less then 1% of PTC’s progress to develop to become more and more aggressive and first become poorly differentiated papillary thyroid cancer and then turn into Anaplastic Carcinomas. 70% of PTC’s take up radioactive iodine (RAI) and so it can be used as part of treatment.
Papillary Micro-carcinomas are PTC’s less then 1cm. In most cases these are found when the thyroid gland is being removed for other reasons such as goiters, benign nodules, cysts, etc… and are found accidentally. The cure rates for these tumors are greater then 99% with no further treatment or surgery. Further treatment is only warranted if there are multiple tumors, spread to the lymph nodes or a history of radiation exposure.
Follicular Variant of PTC is a variant of papillary thyroid cancer with some microscopic differences; but this variant act exactly the same as PTC, is treated in the same way, and has the same type of cure rates.
Follicular thyroid carcinoma (FTC) is the second most common type of thyroid cancer and accounts for about 10% of cases. It tends to happen in women more often in their 40′s and 50′s. Spread to the lymph nodes is very rare, but spread to other parts of the body (lung, bones or liver) is more common then PTC, and happens in 30% of cases. The cure rates for this type of cancer is very good with surgery and when needed radioactive iodine. Patients with minimally invasive FTC (tumors with minimal tumor capsule invasion) have excellent prognosis. 70% of FTC’s absorb radioactive iodine (RAI) and so it can be used as part of treatment.
Hurthle cell cancer is a variant of follicular thyroid cancer and accounts for about 3% of cases. It again happens more often in women in their 50′s and 60′s. It tends to happen more in people who have a family history of this type of cancer. It spreads to the lymph nodes in 25% of cases. Only 10% of this type of cancer absorbs radioactive iodine, so surgery is plays a much bigger role in its treatment. It is more aggressive then follicular thyroid cancer and has a 20-year survival of 70%.
The treatment and management of these types of thyroid cancer are similar, despite the fact that some variants may be more aggressive. If detected early, most papillary and follicular thyroid cancer can be treated successfully, and cured. Important favorable prognostic factors include female gender, age less than 45, tumor being limited to the thyroid gland, size less than 4 cm, and not having the tumor spread to other parts of the body (metastases).
The tables below describe the:
| Table 1. TNM Staging | ||
| T1 | Tumor less then 2 cm in greatest dimension | |
| T2 | Between 2 to 4 cm | |
| T3 | Greater then 4 cm or Minimal Invasion | |
| T4a | Gross Invasion | |
| T4b | Gross Invasion of Pre-vertebral Muscles or Blood Vessels | |
| N0 | No Nodes Involved | |
| N1a | Central Nodes Only (level VI) | |
| N1b | Other Nodes Involved (level I-V or VII) | |
| M0 | No Distant Metastasis | |
| M1 | Distant Metastasis | |
| Age < 45 | Age > 45 | |
| Stage I | M0 | T1N0M0 |
| Stage II | M1 | T2N0M0 |
| Stage III | T1-2,N1aM0T3,N0-1a,M0 | |
| Stage IVa | T1-3, N1b,MO T4a,N0-1b,M0 |
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| Stage IVb | T4b, any N, M0 | |
| Stage IVc | Any T,any N,M1 | |
| Risk Categories |
| Very low risk (Stage I disease): |
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| Low risk (Stage I disease, Stage II >45 years): |
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| Moderate risk: |
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| High risk (Stage III & Stage IV): |
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Table 2. Survival after Diagnosis of Differentiated Thyroid Cancer—National Thyroid Cancer Treatment Cooperative Study Group Risk Factors The most well known cause of thyroid cancer is radiation exposure, either through the environment or as part of treatment for a prior head and neck disorder. Other risk factors are excess iodine consumption and genetic predisposition (family history).
Treatment
Surgery is the only effective way to treat thyroid cancer. Most thyroid cancers are very treatable and carry a high cure rate, especially when discovered early. Treatment of thyroid cancer requires a close collaboration between endocrinologists and thyroid surgeons. The treatment plan by us is always decided through this collaboration. The first and most effective step in treatment of thyroid cancer is surgery. Surgical treatment of thyroid masses includes removal of a portion (hemi-thyroidectomy) or the entire thyroid gland (total thyroidectomy). At the CENTER our philosophy is to individualize the treatment of thyroid cancer. This customized treatment is designed based on your individual condition, pathology, risk category and your endocrinologist’s input.
Papillary and Follicular Carcinoma: In the high-risk category patients, total thyroidectomy is advocated for all patients. The low risk category patients have the option of either undergoing a hemi-thyroidectomy or a total thyroidectomy; the choice surgical approach is very much individualized to the patient’s circumstances. Patients who undergo only a hemi-thyroidectomy for PTC have a much higher risk of recurrence, however the ultimate survival rate does not seem to be affected. The intermediate and high-risk category patients must be treated by a total thyroidectomy (the types of surgery performed at the CENTER is discussed in the next two pages, most patients qualify for minimally invasive thyroidectomy). All patients are placed on post-operative thyroid hormone replacement to suppress the remaining thyroid tissue and prevent any further activity in the gland.
At the CENTER, we perform an Ultrasound of the thyroid gland and the neck immediately before surgery; we find this to be absolutely important to see the size and extent of the tumor in the thyroid and also make sure the tumor has not spread to the lymph nodes. We perform a central compartment neck dissection (or removal of midline neck lymph nodes) in patients at risk and in those patients that have enlarged lymph nodes in this area (we perform the thyroidectomy and the central neck dissection through a minimally invasive technique). If patients also have enlarged lymph nodes in the remaining neck areas, then they will also undergo a modified neck dissection removing the lymph nodes in the lateral aspect of the neck.
Radioactive Iodine (RAI) - Surgery for thyroid cancer is often followed by radiation therapy with radioactive iodine. Again, you and all your physicians working hand in hand decide this course of treatment. Iodine is preferentially absorbed by the thyroid gland, so radioactive iodine specifically targets thyroid tissue (both normal and cancerous thyroid tissue) that may remain after surgery. Radioactive iodine is used to treat only microscopic levels of thyroid cells; it cannot be used as a primary modality instead of surgery. The patients with well-differentiated thyroid cancer undergo RAI treatment 4-6 weeks after surgery. Your endocrinologist carefully plans this out. We will discuss the findings at surgery and plan the RAI with your endocrinologist.
External Beam Radiation - Indications for external beam radiation for thyroid cancer is the following:
1) All tumors with extrathyroidal (outside of thyroid) extension
2) Residual tumor (tumor left behind after surgery)
3) Poorly differentiated thyroid cancer (aggressive type)
4) Anaplastic thyroid cancer.
Follow up - After treatment for thyroid cancer, most patients live quite normal lives. However, we continue to monitor patients very closely and follow their progress frequently along with their primary physician and endocrinologists. Routine blood tests such as thyroglobulin levels (either under thyroid hormone withdrawal or with Thyrogen stimulation) and ultrasound are done for all patients with a total thyroidectomy. Thyroid scans & PET scans also play a role when other tests do not give us a clear answer.
Medullary Carcinoma
Medullary thyroid carcinoma (MTC) accounts for 5-10% of all thyroid cancers, and arise from special cells in the thyroid gland called the parafollicular cells or “C” cells. MTC is easier to treat and control if found before it spreads to other parts of the body. So we must quickly diagnose, prepare the patient and proceed with treatment. There are two types of medullary thyroid cancer: sporadic (80%) and hereditary (passed on through families genetically) (20%).
- Sporadic form: 85% have a single tumor and is only on one side of the gland.
- Hereditary form: 90% have multiple tumors on both sides of the thyroid.
Genetic testing (of the RET proto-oncogene) should be performed in all patients with MTC to determine whether there are genetic changes, as well as children and direct family members of patients with inherited forms of MTC. In individuals with these genetic changes, removal of the thyroid during childhood has a high probability of being curative. The familial forms of MTC are often times associated with other types of tumors (MEN 2A & 2B) and hormonal abnormalities that demand investigation, and preparation before surgery. As such all patients with MTC should be screened for pheochromocytomas (hormone producing tumor), and hyper-parathyroidism (causes high calcium levels in the blood). If a pheochromaocytoma is present it needs to be dealt with first.
| Table 3. MEN Syndromes | |||
| MEN 2A | MTC | Pheochromocytoma | Hyper-parathyroidism |
| MEN 2B | MTC (most aggressive type of MTC) | Pheochromocytoma | Mucosal Neuromas, Marfanoid Habitus (unusually tall & thin) |
Treatment: MTC is a more aggressive tumor and all patients despite the size of the tumor undergo a total thyroidectomy and a central compartment neck dissection. A modified neck dissection of the lateral compartment (side of the neck) is reserved for patients with either a tumor that is larger then 1.5cm or have large lymph nodes in that area. Children of parents with familial MTC who are positive on genetic testing are advised to undergo thyroidectomy as well, to prevent the development of the cancer. In MEN 2A, the surgery should be done before the age of 5, and in MEN 2B shortly after birth.
External Beam Radiation - Indications for external beam radiation for thyroid cancer is the following:
1) MTC with extensive nodal disease (large or more then a few lymph nodes involved)
2) Residual MTC after surgery (tumor could not be completely removed at the time of surgery)
3) All tumors with extrathyroidal extension
Anaplastic Thyroid Carcinoma
Anaplastic thyroid carcinoma is the least common and accounts for only 1–2% of all thyroid cancer. This type is difficult to control and treat because it is a very aggressive type of cancer that rapidly grows and spreads.
Treatment: Surgical treatment for anaplastic carcinoma is total thyroidectomy in rare cases, but despite an aggressive surgical approach the outcome is generally fatal. Chemotherapy regiments are used to prolong life.
Goiter
A goiter is a non-cancerous enlargement of the thyroid. It is usually quite recognizable as a swelling of the lower neck area (Figure 3 & 4).
 Fig. 3 |
 Fig. 4 |
A goiter can sometimes grow so large that it puts pressure on the trachea (windpipe) and esophagus (swallowing tube)
Fig. 5 Thyroid Hormonal Pathway
As a result, patients complain of coughing, a feeling of tightness in the throat, and difficulty breathing and swallowing. Iodine deficiency is one cause of goiter, but is now uncommon in America as iodine is quite plentiful in our diets. Rather, a more common cause is an excess of thyroid stimulating hormone (TSH). This hormone is released from the pituitary gland and regulates the thyroid; it also indirectly regulates the hormones released by the thyroid itself (Figure 6. The thyroid hormonal pathway). When TSH is in excess, the thyroid can become overactive, resulting in goiter.
Smaller goiters can be treated with thyroid hormone therapy in the form of a pill. Once TSH is regulated in this way, the goiter may start to shrink. However, some goiters will not respond to hormone therapy and continue to grow, ultimately causing symptoms such as difficulty swallowing and shortness of breath. Once the patient is symptomatic a partial or complete thyroidectomy (surgical removal of the thyroid) is required to prevent further progression.
Next, learn more about Types of Thyroid Surgery