A study evaluating annual physical examination as a screening method to detect thyroid cancer in cancer survivors exposed to neck radiation has shown a substantial cost reduction compared with ultrasound screening, with no thyroid cancer–related mortality.1 According to the analysis, this method yielded a negative predictive value of 100% for clinically relevant thyroid cancer.
“No clinically advanced thyroid cancer has been missed using this approach,” said Dana Barnea, MD, Survivorship Fellow, Adult Long-Term Follow-Up Program, Memorial Sloan Kettering Cancer Center, New York. “While screening routinely using ultrasound would detect more thyroid cancers, they may be indolent, clinically insignificant cancers, and the annual cost would be substantial.”
Ultrasound Screening and Overdiagnosis
As Dr. Barnea reported at the 2016 Cancer Survivorship Symposium, the prevalence of thyroid nodules in radiation-exposed individuals is purported to be as high as 87%.2 Nevertheless, the vast majority of thyroid nodules are benign, with only a small minority representing thyroid cancer.
Thyroid cancer can be detected either by palpation/physical examination of the neck or ultrasound screening, which is the most sensitive imaging modality for thyroid nodules, or as an incidental finding on imaging (positron emission tomography, computed tomography, magnetic resonance imaging).
According to data from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute, the incidence of thyroid cancer in the United States in the past 3 decades has tripled, and yet, mortality has remained consistently low.3 “The 5-year survival of thyroid cancer is approaching 98%,” said Dr. Barnea. “Is this simply an epidemic of overdiagnosis?”
Study Design and Results
Dr. Barnea and colleagues reviewed all of the medical records of childhood and young adult cancer survivors seen at the survivorship clinic between 2005 and 2014 and included all patients with radiation to the neck. Those patients who had a diagnosis of thyroid cancer or thyroid nodules prior to their first visit in the clinic were excluded.
The final cohort consisted of 585 survivors who underwent an annual physical examination. If the exam was abnormal, the patient was then referred for thyroid ultrasound screening.
Of the 585 survivors examined, clinicians palpated at least 1 thyroid nodule in 40 survivors, 39 of whom received at least 1 ultrasound examination over a median of 3.1 years of follow-up in the clinic. Suspicious features on these ultrasound examinations led to a fine-needle aspiration of the nodule in 24 of the survivors.
Screening Modalities for Thyroid Cancer
- Physical examination of 585 cancer survivors previously exposed to neck radiation led to ultrasound screening in 39 survivors, 7 of whom had papillary carcinoma.
- No thyroid cancer–related mortality occurred, and the negative predictive value for clinically relevant thyroid cancer was 100%.
- With yearly ultrasound screening of this entire population, costs would have increased from $27,000 to $574,100.
The fine-needle aspiration results were benign in 15 survivors, inconclusive in 1, and malignant or suspicious in 8, Dr. Barnea reported. These nine survivors were then referred for thyroidectomy, which revealed benign adenoma in two patients and papillary carcinoma in seven patients.
“We conducted 106 ultrasound examinations altogether,” said Dr. Barnea. “Using the Medicare price of ultrasound, this costs approximately $27,000. However, had we decided to perform yearly ultrasound screening, this cost would have increased to over half a million dollars.”
Further Study
Dr. Barnea and colleagues plan to continue prospective follow-up of this cohort and to perform cost analysis and microsimulation modeling of thyroid cancer screening.
“We are in the process of assessing thyroid cancer mortality in the Childhood Cancer Survivor Study,” Dr. Barnea concluded. “There are studies underway to evaluate active surveillance of small, asymptomatic papillary carcinomas and to better risk stratify with fine-needle aspiration to avoid false-positives and unnecessary thyroidectomies using molecular and genetic fingerprints of malignancy.” ■
Disclosure: Dr. Barnea reported no potential conflicts of interest.
References
1. Barnea D, Tonorezos ES, Moskowitz CS, et al: Neck radiation, thyroid cancer, and avoiding harm. 2016 Cancer Survivorship Symposium. Abstract 254. Presented January 15, 2016.
2. Schneider AB, Bekerman C, Leland J, et al: Thyroid nodules in the follow-up of irradiated individuals: Comparison of thyroid ultrasound with scanning and palpation. J Clin Endocinol Metab 82:4020-4027, 1997.
3. Davies L, Welch HG: Current thyroid cancer trends in the United States. JAMA Otolaryngol Head Neck Surg 140:317-322, 2014.
