Published in:
01-12-2008
PET Scan Valuable in Subset of Patients with Negative I-131 Scan, Rising Thyroglobulin Levels in Differentiated Thyroid Cancer Patients
Published in: World Journal of Surgery | Issue 12/2008
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We wish to note our appreciation and to congratulate Dr. Grant and colleagues [1] for their critical analysis of the role of the positron emission tomography (PET) scan in patients with papillary thyroid carcinoma (PTC) with recurrence after surgery and radioactive iodine (RAI) therapy. We recently discussed their article in our journal club, and it generated great enthusiasm among the group. Some members of the group had a few questions that I am forwarding to you for clarification.
1.
In the authors’ experience [1], PET has a modest benefit over ultrasonography (USG) in evaluating re-operative PTC patients. It is unclear which patients in their series underwent PET scan study. Did only I-131 scan negative patients undergo a PET scan study, or did all patients have PET scans irrespective of I-131 scan study results and thyroglobulin (Tg) values? It has been reported that PET/CT offers improved diagnostic value in follow-up of differentiated thyroid cancer (DTC) patients with elevated Tg and a negative I-131 scan [2].
2.
The authors mentioned that there were a few false positive uptake studies. We wish to know what specific lesions led to the false positive uptakes. Were any of these benign or inflammatory lesions, or were they something else [3]?
3.
In the study reported by Grant et al., a few patients who had high levels of anti-thyroglobulin antibodies also had false negative results on the PET scan. We wish to know how high anti-Tg antibodies interfere with the uptake mechanism during a PET scan.