Columbus, OH - March 2016
Pediatric cancer survivors are at risk of subsequent malignancies, and thyroid cancers account for about 10 percent of those secondary cancers. So a reliable way of detecting thyroid nodules in follow-up care is important for the ongoing health of that population, particularly those who have had head and neck radiation exposure.
But a recent prospective study from clinician-researchers at Nationwide Children’s Hospital finds that the current standard of care – a yearly thyroid physical examination – misses a substantial number of nodules in survivors.
Out of 119 pediatric cancer survivors enrolled in the study, ultrasound found 33 patients (27.7 percent) with at least one thyroid nodule >0.3 cm in size, which was considered the threshold for possible clinical significance. Physical examination detected nodules in only two of the 33 patients identified by ultrasound. Almost all (95 percent) of the physical exams were conducted by oncologists specifically designated and trained in thyroid examinations as part of the research study.
A total of 11 patients had nodules ≥ 1 cm in size, triggering biopsies under institutional guidelines. Physical examination detected none of these nodules. One patient was diagnosed with papillary thyroid carcinoma and underwent a complete thyroidectomy. A complete thyroidectomy was performed on another patient after the biopsy revealed a follicular neoplasm. Later pathology showed a hyalinizing trabecular tumor.
“Our results certainly show the limitations of the physical exam,” says Sarah H. O’Brien, MD, senior author of the study and a member of the Section of Hematology, Oncology and Blood and Marrow Transplant at Nationwide Children’s. “When you have a high risk population, particularly those who have had head and neck radiation, thyroid ultrasound is really what is needed to screen these patients.”
The study was also designed to determine prevalence of thyroid nodules in patients whose treatment had included radiation and chemotherapy vs. those who were treated with chemotherapy alone. Approximately 37 percent, or 22 of 60 patients in the radiation group, were found to have nodules > 0.3 cm in size. Approximately 19 percent, or 11 out of 59 patients in the chemotherapy alone group, were found to have nodules.
“We went into this study thinking that we were going to find many nodules in patients with radiation, but not very many in our control population,” says Dr. O’Brien. “I was surprised with how many we found in the chemotherapy-only community. We don’t know if there is something about chemotherapy alone that predisposes childhood cancer survivors to develop thyroid nodules, or if thyroid nodules are simply more common than we realize in the general population.”
The initial cancer diagnoses in the radiation and chemotherapy group were predominately Hodgkin lymphomas, brain tumors and acute leukemias, while the initial diagnoses in the chemotherapy alone group were sarcomas and leukemias. Each patient had completed treatment at least three years before enrolling in the study, though the time between completion of treatment and detection of nodules was more than 25 years in some cases.
Both patients who had thyroidectomies were members of the radiation and chemotherapy group.
“It is important to find a balance,” says Dr. O’Brien, who is also an associate professor of Pediatric Hematology/Oncology at The Ohio State University College of Medicine. “You don’t want to blindly screen patients who have already had cancer once. You don’t want to alarm patients and families with what turn out to be insignificant nodules. You also don’t want to miss patients who do have secondary thyroid cancer.”
“Ultrasound is a necessary tool,” she continues. “Our study raises several additional questions. Which patients should undergo thyroid ultrasound? How long after our patients complete cancer therapy should we start screening? How often should we screen?”
The researchers intend to follow the cohort of patient for the next five to ten years and continue to assess thyroid nodule development and progression.
Agrawal C, Guthrie L, Sturm MS, Stanek J, Martin L, Henwood-Finley M, Aldrink JH, Olshefski R,O'Brien SH. Comparison of thyroid nodule prevalence by ultrasound in childhood cancer survivors with and without thyroid radiation exposure. Journal of Pediatric Hematology/Oncology. 2016 Jan;38(1):43-8.