SPECT/CT Improves Staging, Risk Stratification of Thyroid Cancer

“In this article I aimed to highlight the role of radioiodine imaging in risk stratification of patients with thyroid cancer and to assess the contribution it brings to the completion of staging and the decision to omit or proceed with I-131 [iodine-131] therapy,” said Anca M. Avram, MD, clinical associate professor of endocrinology at the University of Michigan Medical School (Ann Arbor, USA), and author of the study. “The new technology of SPECT/CT has substantially improved the interpretation of planar studies and can be implemented in the postoperative management protocols of thyroid cancer patients.”

SPECT/CT has typically been utilized for imaging thyroid cancer patients after radioiodine therapy, with the benefits of considerably reducing the number of equivocal foci seen on planar imaging alone, determining lymph nodal status more accurately than planar imaging and improving anatomic localization of activity foci visualized on planar imaging. Studies cited in the article report on the high diagnostic value of radioiodine SPECT/CT, resulting in changes in risk stratification and clinical management in a substantial number of patients (ranging between 25%-47% of patients).

More recently, SPECT/CT has been utilized prior to radioiodine therapy to better identify and characterize focal activity seen on planar scans for differentiating between metastatic lesions and benign uptake in residual thyroid tissue or normal organs. Information acquired with preablation SPECT/CT scans can be used in addition to histopathology data to fulfill staging and risk stratification prior to radioablation. The preablation scans can reveal unsuspected regional and distant metastatic lesions, resulting in changes in the prescribed I-131 activity, either by adjusting empiric I-131 doses or performing dosimetry calculations.

The article reports that SPECT/CT changed postsurgical staging in 21% patients, modified the treatment approach in 36% patient with disease, and led to avoidance of unnecessary I-131 therapy in 20% patients without disease. The findings on preablation scans altered the recommended I-131 therapy in 58% patients as compared to therapy based on histopathologic risk stratification alone, by correctly prescribing higher activities for treatment of regional and distant metastases and minimizing the activity prescribed for thyroid remnant ablation.

SPECT/CT is also very useful for evaluating unusual radioactivity distributions in thyroid cancer patients; accurate anatomic localization of radioactivity foci permits rapid exclusion of physiologic mimics of disease, or confirmation of metastatic lesions to unexpected sites.

“Diagnostic radioiodine scintigraphy with SPECT/CT provides a clear advantage for the management of patients with thyroid cancer,” said Avram. “By integrating clinical, pathology and imaging information, the nuclear medicine physicians are able to offer an individualized treatment plan, bringing the nuclear medicine community a step closer to the goal of personalized medicine.”

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