Clinical impact of Ga-DOTATATE PET-CT imaging in patients with medullary thyroid cancer.

PURPOSE

Medullary thyroid cancer (MTC) arises from neuroendocrine C cells of the thyroid. There is no single diagnostic imaging method that can reveal all MTC recurrences or metastases. Ga-DOTATATE is an alternative PET radiotracer that showed acceptable efficacy in the detection of MTC. In this study, we aimed to reveal the clinical efficacy and impact of this radiotracer on the management of patients with MTC.

METHODS

The Ga-DOTATATE PET-CT records of 38 patients with confirmed MTC were included in the study. The demographic data, clinical indication for the scan, previous therapies, and tumor marker levels were recorded. The site and SUVmax of the lesions were also noted. A consensus was reached on the additional value of Ga-DOTATATE PET-CT, and sites with discordant results on conventional imaging (CI). Finally, changes in management after the scan were evaluated.

RESULTS

Ga-DOTATATE PET-CT outperformed CI in 14/38 (37%) patients. In these 14 patients, metastatic lymph nodes were detected in 8, bone metastases in 4, and both bone and lymph nodes metastases in 2 patients. In 16/38 (42%) patients, Ga-DOTATATE PET-CT performed equally well as CI. In 5/38 (13%) patients, CI outperformed PET-CT. Most of the patients (4/5) in this group had hepatic metastases. Ga-DOTATATE PET-CT positivity was also correlated with tumor marker expression [median calcitonin; PET-positive: 743 ± 5439 vs PET-negative: 45 ± 17 (p:0.012), median CEA; PET-positive: 41 ± 162 vs PET-negative: 2.6 ± 1.4 (p:0.015)]. Ga-DOTATATE PET-CT changed the clinical management of 13/38 (34%) patients. The information provided by PET-CT resulted in neck surgery in 5/13 patients, external radiotherapy in 3/13 and both in one patient. Four of these thirteen patients were found to be eligible for peptide receptor radionuclide therapy.

CONCLUSION

Ga-DOTATATE is an essential part of the work-up for patients with MTC. This modality outperformed CI in 14/38 (37%) patients and changed the clinical management in 13/38 (34%) patients. Prospective randomized studies with image-guided therapy decisions are needed to further reveal the impact of PET imaging in patients with MTC.