JNM: Follow-up scintigraphy unnecessary in high-risk thyroid cancer

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Follow-up diagnostic radioiodine whole-body scintigraphy (DxWBS) does not help detect thyroid cancer recurrence in a high-risk population, according to a study published in this month's Journal of Nuclear Medicine.

The follow-up protocol for differentiated thyroid carcinoma consists of lifelong follow-up because of the risk of recurrence. The conventional model, which paired periodic assessment of thyroglobulin and thyroglobulin antibody levels and performance of thyroid-stimulating hormone (TSH)-stimulated thyroglobulin measurement with DxWBS six to 12 months-post-treatment, has been modified. American and European guidelines no longer recommend follow-up DxWBS for low-risk patients. However, the role of DxWBS in high-risk patients has not been revisited, partially due to lack of studies in this patient population.

Siegrid G. de Meer, MD, of the department of surgery at University Medical Center in Utrecht, the Netherlands, and colleagues designed the study to investigate the additional value of scintigraphy in patients at high-risk for recurrence.

Researchers retrospectively examined 112 high-risk patients (70 percent female; median age, 48 years) who had undergone surgery for thyroid carcinoma and had been referred to the nuclear medicine department for 131I ablation. de Meer and colleagues relied on the American guidelines to characterize patients as high-risk, targeting those with T3 or T4 tumors or positive cervical lymph nodes (N1).

“Most patients had a thyroglobulin value above the lower detection limit of 0.2 ng/mL (66 percent). Only eight patients had a thyroglobulin value above 0.2 ng/mL in combination with positive DxWBS results,” reported de Meer and colleagues. All eight patients were diagnosed with recurrent disease.

DxWBS results corresponded to laboratory findings among the 31 patients with thyroglobulin measurements below 0.2 nG/mL; scintigraphy showed no signs of recurrent disease.

The authors calculated a negative predictive value of 100 percent for stimulated thyroglobulin levels less than 0.2 nG/mL for disease recurrence and concluded that “routine DxWBS added no diagnostic value to stimulated thyroglobulin level measurement in a large population of patients with high-risk differentiated thyroid carcinoma.”

However, de Meer and colleagues did offer that DxWBS provides one diagnostic imaging option for patients with detectable thyroglobulin (more than 2 ng/mL) in addition to blind therapeutic activities, F18-FDG PET, 124I PET, CT and MRI.