Role of Tc-99m DMSA (V) scanning and serum calcitonin monitoring in the management of medullary thyroid carcinoma.

Introduction: Medullary thyroid carcinoma (MTC) is a rare disease. Serum calcitonin levels and Tc-99m DMSA (V) scans are used in the follow-up of these patients after surgical resection. We present our experience in the follow-up of these patients at a tertiary institution.
Methods: A retrospective review of the medical records was performed. Patients with histologically-proven MTC, and who had serum calcitonin assays and DMSA (V) scans in their postoperative follow-up, were included.
Results: There were 17 patients with 56 DMSA (V) scans. Four out of seven patients with elevated preoperative calcitonin measurements had calcitonin normalisation within six months of surgery, and have remained disease-free. Two patients had persistently elevated calcitonin levels after six months, which predated positive DMSA (V) scans. Results of DMSA (V) scans and serum calcitonin levels were concordant in 38 of 48 instances (79.2 percent) and discordant in 10 of 48 instances (20.8 percent). Sensitivity of DMSA (V) scans for detecting recurrence was 71.4 percent. There were no false-positive scans.
Conclusion: Serum calcitonin level is a sensitive and specific indicator of disease recurrence in postoperative follow-up of patients with MTC. Early (within six months) normalisation of calcitonin levels postsurgery may predict subsequent disease-free status. Discordant results between serum calcitonin levels and DMSA (V) scans may be due to undetectable lesions and follow-up scans or alternative radionuclide imaging may be required.