Information obtained from single positron emission computed tomography (SPECT)/computed tomography (CT) scans helps determine the need for radioiodine therapy in persons with thyroid cancer and influences the long-term follow-up strategy for such patients, according to research presented in The Journal of Nuclear Medicine (2012;53:754-764).
“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,” affirmed report author Anca M. Avram, MD, of the Division of Nuclear Medicine/Radiology at University of Michigan Medical Center in Ann Arbor, in a statement issued by the Society of Nuclear Medicine (SNM).
For many years, postoperative management of persons with thyroid cancer included radioiodine administration followed by a post-therapy scan, explained Avram in her research paper. However, this approach has been challenged by evidence that remnant ablation does not improve survival in low-risk patients.
As noted in the SNM statement, SPECT/CT can determine lymph node status following radioiodine therapy more accurately than can planar imaging in persons with thyroid cancer, and SPECT/CT also improves anatomical localization of activity foci seen on planar imaging. In her report, Avram cited studies that speak to the high diagnostic value of radioiodine SPECT/CT: Such information resulted in changes in risk stratification and clinical management in a substantial number of patients.
Specifically, in various studies of persons with thyroid cancer, SPECT/CT imaging:
- changed postsurgical staging in 21% of patients
- modified the treatment approach in 36% of patients
- altered the recommended radioiodine 131I therapy in 58% of patients compared with therapy based on histopathologic risk stratification alone, due to findings on preablation scans
- accurately characterized 85% of foci considered inconclusive on planar imaging, resulting in altered management for 47% of patients
- led to the avoidance of unnecessary 131I therapy in 20% of patients without disease.
Avram also noted that SPECT/CT is very useful in evaluating unusual radioactivity distributions in persons with thyroid cancer and in confirming metastases to unexpected sites.