Current Issues in Thyroid Cancer, With Dr. John C. Morris
John C. Morris, III, M.D. is a Rochester, Minnesota-based board-certified endocrinologist at the Mayo Clinic’s division of Endocrinology, Diabetes, Metabolism, and Nutrition, and a past director of the American Thyroid Association. Dr. Morris works with thyroid cancer patients, is an active researcher in the field, and has published a number of journal articles highlighting his research findings on thyroid cancer. Dr. Morris graciously agreed to share his thoughts with HealthCentral via phone interview about some of the current issues of interest to thyroid cancer patients, including whether thyroid cancer is being over diagnosed, the role of active surveillance versus surgery, ultrasound versus fine needle aspiration biopsy, and the role of genetic and molecular testing.
Is there actually more thyroid cancer, or is it overdiagnosis due to better detection?
Thyroid cancer is one of the few cancers in the United States that appears to be increasing. The controversy has focused on whether the actual rate of thyroid cancer is increasing, or whether more cancer is being detected. The conclusion of most experts is, however, that an increased use of various imaging has increased the detection — and as a result, the diagnosis and treatment — of low-risk thyroid cancer.
According to Dr. Morris:
“We've come to realize that there are millions of people walking around who are happy and healthy who have very small papillary thyroid cancers — micropapillary cancers of 1 cm or less — that are confined to the thyroid and haven't spread to lymph nodes. It also seems clear that the majority of those people who have those little cancers will live the rest of their lives and never know they had cancer unless it's discovered incidentally due to unrelated imaging.
This incidental discovery is common. Cancerous nodules are found incidentally as a result of a CT (computerized tomography) scan, carotid ultrasound, or PET (positron emission tomography) scan, for example. If they are small cancers, don’t cause symptoms, and are not likely to be a threat, this is where a risk of overdiagnosis and overtreatment comes in.”
Given this knowledge, the issue is whether your low-risk thyroid cancer should be treated — or simply monitored.
Is active surveillance a viable treatment for low-risk papillary thyroid cancer?
As noted, most experts agree that the increasing rate of diagnosis is due to the incidental discovery of small, cancerous thyroid nodules. The majority of these nodules are localized, low-risk papillary thyroid cancer, which has a 99 percent survival rate after 20 years. Even though this type of cancer is very slow-growing and has an excellent prognosis, it is usually treated very aggressively, with surgical removal of the thyroid gland and radioactive iodine (RAI) ablation.
Some experts, including Dr. Morris, are now recommending that your treatment options include “active surveillance” — sometimes called “watchful waiting” — for small (1 cm or less in size), slow-growing, low-risk papillary thyroid cancer. Dr. Morris explains:
“There is a movement toward being less aggressive about these small, non-threatening thyroid cancers. If the thyroid cancer is not dangerous and won’t cause a problem, we can argue that any treatment is more than is actually needed. And, for the majority of these patients, taking out the thyroid is more than needed. If surgery is called for, it can be limited, such as surgically removing only part of the thyroid in a lobectomy.”
An important part of active surveillance, however, is regular ultrasound monitoring. Says Dr. Morris:
“The nodules can be observed and followed with ultrasound. If they start to grow, they can be addressed and treated. Data suggests that treatment at a later date is as effective as if treated earlier.”
For low-risk papillary cancer, the choice of active surveillance versus surgical removal is ultimately yours. Says Dr. Morris:
“Some patients want the cancer removed. Others prefer to watch if it’s sitting there doing nothing. We also have some new ablative type procedures such as alcohol ablation that allow us to treat a cancerous nodule in a less expensive and invasive way compared to surgery.”
When is fine needle aspiration biopsy needed, versus ultrasound?
In recent years, ultrasound technology has improved, and the images are sharper and the resolution is higher. In some cases, physicians are increasingly relying on ultrasound to rule out suspicion about nodules, bypassing the fine needle aspiration (FNA) biopsy process. At the same time, some research is showing that ultrasound features are not a truly accurate predictor of thyroid cancer. Is FNA always necessary?
Dr. Morris explains the criteria for FNA:
“Because of the improvements in ultrasound technology, we do first rely on ultrasound to decide which nodules need to be biopsied. Our criteria for biopsy have changed because we are getting better information from the ultrasound imaging. Theguidelines from the American Thyroid Association (ATA) are well done, and provide a good description of nodules that are clearly benign on ultrasound and don’t require FNA, such as purely cystic (fluid-filled) nodules, or nodules that are spongiform, and resemble a sponge. These are usually benign and have a low risk for malignancy. The ATA says not to perform an FNA if a nodule is 1 cm or less in size, but not everyone agrees. In some cases, we still might biopsy smaller nodules to clarify discussion with the patient.”
Ultimately, if you have thyroid nodules, it’s important to consult with a knowledgeable endocrinologist, who can determine whether FNA is recommended in your case, based on your ultrasound results, and the latest research findings.
Should all patients who are undergoing fine needle aspiration biopsy have genetic testing?
One relatively new development in the process of diagnosing thyroid cancer is the increasing use of molecular and genetic testing. In the past, if an FNA biopsy was inconclusive or indeterminate and cancer could not be diagnosed or ruled out definitively, the next step was surgery to remove the thyroid gland. At that point, a pathological assessment of the gland could be done to make a definitive diagnosis. The downside of this process was that some 30 percent of thyroid biopsies are indeterminate. Those people typically underwent surgery to remove the thyroid gland, making them permanently hypothyroid. Among those people, however, only 20 to 30 percent turned out to have thyroid cancer, so 70 to 80 percent had what was essentially an unnecessary surgery to remove the thyroid gland. With an estimated 450,000 annual thyroid biopsies, this means that there could be around 100,000 unnecessary thyroidectomies each year for benign thyroid nodules.
Genetic testing tries to give you a better estimate of the risk of cancer. This testing — including the Afirma Thyroid FNA Analysis from Veracyte — performs molecular/genetic analysis on indeterminate samples to diagnose or rule out thyroid cancer. This test is known as a gene expression classifier or GEC. With an indeterminate FNA result, your risk of cancer may be as high as 20 percent. If you do the genetic test on that sample and it’s negative, this reduces your risk of cancer to about 5 percent. As a result, the number of surgeries performed to assess indeterminate nodules can be dramatically reduced.
When a test like the Afirma analysis is planned, your FNA biopsy samples are sent directly to Veracyte, and their pathologists do the first pass assessment. If the results are indeterminate, then they perform the genetic testing.
It might seem as if it makes sense for all biopsies to undergo genetic testing. According to Dr. Morris, however, the FNA is usually a good test and the genetic testing process is not necessarily needed for a first FNA. This is especially true if you have access to experienced cytopathology.
“If you are in a location where your FNA will be evaluated by top cytologists who are experienced in a higher volume of thyroid biopsies, it is reasonable not to include a sample for genetic testing in the beginning.”
Dr. Morris notes that genetic testing is, however, especially helpful in several situations.
“There are some types of nodules — follicular neoplasms and adenomas, for example — where FNA may not be as effective and indeterminate results are more likely. Also, if you are older, in your seventies for example, and not a good surgical candidate, genetic testing of an inconclusive nodule can also be useful.”
A good guideline: If you are in an area where you don’t have access to experienced cytopathologists, you may want to consider having the genetic testing on your first FNA. If you are in an area where your FNA results can be interpreted by more experienced experts, talk to your doctor about whether or not genetic testing is warranted in your case.
Telephone interview with Dr. John Morris, August 31, 2017
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