Finding Unsuspected Thyroid Cancer Through Routine Imaging Studies
Routine imaging studies of older patients are finding thyroid nodules that may be malignant before they cause signs or symptoms of the disease according to a study by surgeons at Rush University Medical Center presented at the 2008 Clinical Congress of the American College of Surgeons.
According to findings from the study, elderly patients were two times more likely to be diagnosed with thyroid cancer than younger patients while undergoing imaging examinations for other reasons. Thyroid cancer was found incidentally in 41 percent of patients over the age of 65 compared with 22 percent of younger patients. The study included 241 elderly thyroid cancer patients and 41 younger patients who were treated for the disease at Rush University Medical Center.
"Older patients are much more likely to receive imaging testing. As patients get older, they have their spine evaluated for degenerative arthritis and other spine conditions or imaging studies for chest problems. The same is true with ultrasound Doppler evaluation of the carotid artery for arteriosclerosis. So this group is much more likely to have a thyroid nodule discovered incidentally on some other type of imaging study, and rather than saying it's probably nothing, physicians have to pursue it," said Dr. Richard A. Prinz, chair of the department of general surgery at Rush.
Results from the study also confirmed that older patients with thyroid cancer have a worse prognosis. Elderly patients tended to have larger tumors, higher rates of distant metastases, and shorter times to recurrence of disease than younger patients in the study.
According to study authors, primary care and other physicians who review imaging studies of elderly patients should carefully evaluate any suspicious anatomic features in the thyroid, such as any nodules that are larger than a centimeter or have an irregular border or internal vascularization.
"Once we find a nodule in the thyroid, we can't put our heads in the sand and ignore it. We have to look at all the imaging characteristics on incidental scans and, if need be, do an ultrasound of the thyroid, which is the best imaging way to evaluate the thyroid gland. If there are worrisome features, we need to do a fine needle aspiration biopsy of the nodule. This approach holds true for younger and well as older patients, but since elderly patients are more likely to have cancer, there should be greater concern and more willingness to evaluate any nodules found on imaging scans," said Prinz.
Most forms of thyroid cancer can be treated effectively by surgically removing the thyroid gland as well as any involved lymph nodes in the neck. Radio-iodine therapy is given to ablate any remaining thyroid tissue, particularly for patients who have tumors that are larger than a centimeter or have disease that has spread to the lymph nodes and surrounding tissue. Doses that suppress the release of thyroid stimulating hormone also may be given.
"For elderly patients, these treatments are rather benign. Radio-iodine therapy is not like a typical course of chemotherapy that causes hair loss and increases the risk of developing an infection. The operation is safe and has a low level of complications. Treatment should not be ruled out, therefore, because of the age of the patient," said Prinz.
The incidence of thyroid cancer has been steadily rising. Since the 1970s, there has been more than a two-fold increase in the number of new cases of thyroid cancer detected each year in the United States. Thyroid cancer accounts for 1 percent of all malignancies and 0.3 percent of all deaths from cancer among elderly patients. Yet only 5 percent of thyroid nodules that can be felt by a physician during a physical examination are diagnosed as malignant, and less than 0.1 percent exhibit signs and symptoms that may be detected in the elderly.