Purpose: The aim of the present study was to evaluate the possible diagnostic role of the combined performance of BRAF mutation analysis and MIBI scintigraphy in papillary thyroid cancer (PTC) patients with incomplete bio-chemical response to first radioiodine therapy (RAIT) performed for thyroid remnant ablation.
Methods: The records of 15 PTC patients with bio-chemical incomplete response to first RAIT were retrospectively analyzed. BRAFV600E analysis on primary tumor samples was obtained in all cases along with neck ultrasonography and 99mTc-MIBI scintigraphy of the neck-thorax regions at first follow-up. All patients then underwent RAIT with high radioiodine activities. A post-therapy whole-body scan (pT-WBS) was acquired 5-7 days after RAIT.
Results: Abnormal radioiodine uptake was found in 10 out of the 15 patients (67%, 131I+ve), while in the remaining 33%, no abnormal radioiodine uptake was detected (5/15, 131I-ve). Abnormal tracer uptake was found in 6 out of 10 131I+ve patients at 99mTc-MIBI scintigraphy (MIBI+ve). BRAFV600E mutation was not found in the majority of 131I+ve patients (9 out of 10 BRAFV600E-ve). On the contrary, in the 5 131I-ve patients, 99mTc-MIBI scintigraphy did not show any abnormal tracer uptake (MIBI-ve), while BRAFV600E mutation was present (BRAFV600E+ve). Thus, in our series, the association between MIBI-ve scintigraphy and BRAF+ve mutation was a useful diagnostic tool in predicting negative pT-WBS outcome.
Conclusion: Albeit obtained in a small retrospective series, our results suggest that the combination of BRAFV600E+ve mutation and MIBI-ve scintigraphy may be considered a negative prognostic clue, which predicts the absence of radioiodine uptake at pT-WBS in DTC patients with incomplete bio-chemical response to first RAIT.
Keywords: 99mTc-MIBI scintigraphy; BRAFV600E; Bio-chemical incomplete response; Metastatic thyroid cancer.