Post I-131 therapy scanning in patients with thyroid carcinoma metastases:: An unnecessary cost or a relevant contribution?

Rationale: In patients with elevated serum thyroglobulin (Tg) and a negative whole-body scan (WBS), posttherapy scanning can reveal metastases in many cases and is therefore recommended. In contrast, the routine use of posttherapy scanning is questioned. Materials and Methods: One hundred six patients with differentiated thyroid carcinoma had pre- and posttherapy scanning, with metastatic uptake on the diagnostic scan and were divided into 2 groups: 60 patients assessed on first ablation after thyroidectomy and 46 patients with tumor persistence or recurrence after initial ablative therapy. Data modifying the disease stage or treatment were considered to be clinically relevant. Results: Posttherapy scanning on first ablation changed the disease stage in 8.3% of the patients and therapeutic approach in another 15%, and provided clinically relevant information for 26% of patients with 1 previous ablation. Even when excluding cases whose lesions were known by the time of the first postablative scan, the therapeutic approach, was influenced by posttherapy scanning in 15.6% of the patients. Only 4 of 211 metastases detected on pretherapy WBS did not appear on postablative scans. Conclusions: Posttherapy scanning provides important information, even in patients whose pretherapy WBS is positive for metastases, with this approach being useful both during the first ablation and subsequent treatments.