Physical Exams Adequate to Detect Thyroid Cancer in Cancer Survivors

The use of a standard yearly physical examination to screen for thyroid cancer among high-risk survivors of childhood and young adult cancers resulted in a negative predictive value of 100% for clinically relevant thyroid cancer and a significant cost savings compared with regular ultrasound screening, according to the results of a study presented at the 2016 American Society of Clinical Oncology (ASCO) Cancer Survivorship Symposium (abstract 254).

“We know that screening routinely using ultrasound would probably detect more thyroid cancers,” said presenter Dana Barnea, MD, a medical oncologist from the department of medicine at Memorial Sloan Kettering Cancer Center. “However, these may be indolent, clinically insignificant cancers.”

According to Barnea, the prevalence for thyroid nodules in the general population is between 13% and 67%. In contrast, in individuals exposed to radiation to the neck, the prevalence can be as much as 87%. The vast majority of these thyroid nodules are benign with only a small percentage representing cancer.

Thyroid nodules are detected using palpation during a physical exam, imaging with ultrasound, or can be seen as incidental findings during other imaging procedures. Current guidelines from the Children’s Oncology Group recommended a yearly physical exam to screen for thyroid cancers among cancer survivors who were exposed to radiation; however, other guidelines call for the use of regular ultrasound imaging to screen the thyroid. According to Barnea, regular ultrasound may have several potential harms including false positive tests, overdiagnosis and overtreatment, and cost.

At Memorial Sloan Kettering Cancer Center, a long-term follow-up program has been established for high-risk survivors of cancer that was diagnosed prior to age 40. All survivors exposed to radiation of the neck undergo an annual physical examination. If the exam is abnormal, patients are referred to thyroid ultrasound. If there are suspicious features on ultrasound, the patient is referred for fine needle aspiration. If the aspiration is suspicious or malignant the patient is referred for surgery; if it is inconclusive, the fine needle aspiration is either repeated or the patient is referred for surgery.

Barnea and colleagues conducted a retrospective analysis to evaluate if this screening algorithm was an effective method for screening these high-risk patients. This study looked at all adult survivors treated for childhood or young adult cancer with radiation including the neck evaluated in the Adult Long-Term Follow-Up Program between November 2005 and January 2015 (n = 1,069). The final analysis included 585 eligible adults (those with radiation to the neck without thyroid cancer or nodules prior to first study visit).

Upon examination, 6.8% of survivors (40 patients) had a thyroid nodule palpated. This occurred a median of 21.7 years from the time of radiation. Half of patients with a palpable thyroid nodule had an original diagnosis of Hodgkin lymphoma. In addition, patients with a palpable thyroid nodule were more likely to be women and to be older.

Thirty-nine patients underwent ultrasound follow-up. One-third of patients did not require a fine needle aspiration. Fine needle aspiration performed in the remaining 24 patients revealed benign nodules in 15 patients, an inconclusive nodule in one survivor, and malignant or suspicious nodules in eight survivors. Nine of the survivors were referred on to surgery. Surgery revealed benign adenomas in two patients and papillary carcinoma in seven patients.

Barnea said that the negative predictive value of annual palpation was 100% with no thyroid cancer detected within 1 year of a negative palpation. Between 2005 and 2014, the 585 survivors had 2,277 yearly visits.

“If we take these 2,277 yearly visits we know that we conducted 106 ultrasound examinations all together, using the Medicare cost of ultrasound this cost approximately $27,000,” Barnea said. “However, had we decided to performed yearly ultrasound screening this cost would have increased to over half a million dollars.”

Barnea acknowledged that because Memorial Sloan Kettering Cancer Center is such a large institution, these results may not be generalizable to other institutions.