Breaking the 2015 ATA Recommendation for Medullary Thyroid Cancer (MTC) Guidelines. Case Report

Abstract

Abstract Male patient, 49 years old. Thyroid US with a suspicious nodule. Fine Needle Aspiration Biopsy (FNAB) suggest MTC, with a pre-operative serum calcitonin (CTN) of 591 pg/mL. Total thyroidectomy with central and bilateral dissection was performed. Biopsy. Results: MTC in left thyroid nodule of 2,6 cm without metastasis in 29 lymph nodes. In the follow up, undetectable serum CTN for 6 years. In 2015 serum CTN of 4.7 pg/mL and Carcinoembryonic antigen (CEA) 1.2 ng/mL. Evolution of serum markers in table 1. Along with the rise of markers, the neck US showed bilateral subcentimetric LN in the group IV. In the follow-up, the size is stable; FNAB of the LN in different centers don′t show any sign of malignancy, along with undetectable CTN levels in the sample. The doubling time of CTN and CEA (March 2020): 16 and 51.3 months respectively. Given the lack of cervical compromise and going against MTC ATA 2015 recommendations, a neck and thorax CT, hepatic MRI and bone scintigraphy were ordered, despite not presenting CTN levels >150 pg/mL. The hepatic MRI shows 3 hypervascular hepatic lesions, which are recommended to be contrasted with a liver-specific agent (gadoxetic acid) to improve characterization of the lesions. Thanks to this procedure, 4 focal lesions are discovered, one larger than 10 mm, without contrast agent retention, suggests metastasis. PET 68Ga-DOTATATE: 2 focal lesions with overexposure of somatostatin receptors in the hepatic parenchyma, which correlate to known lesions, with SUVmáx of 6,8 y 7,3. After an evaluation by a surgeon, surgery is done in July 2020 removing 5 lesions; the biopsy confirmed MTC metastasis. Conclusions: the clinical guidelines may give general direction and allow to manage cases based on evidence; however, they must always be used considering the context of each particular case. In this one, if the guidelines had been strictly followed, it would not have been possible to detect the hepatic metastases within the window of opportunity to achieve a surgical resection with curative intent. Table1. Mar15 CTN 7,3 Pro- CTN 0,12 CEA 1,2. Oct15 CTN 16,1 Pro- CTN 0,15 CEA 0,7. Jan16 CTN 17 Pro- CTN 0,18 CEA 0,5. Jul16 CTN 17,9 Pro- CTN 0,18 CEA 1,6. Nov16 CTN 20,7 Pro- CTN 0,33 CEA 1,8. Aug17 CTN 35,2 Pro- CTN 0,4 CEA 1,8. Jun18 CTN 42,5 Pro- CTN 0,34 CEA 1,8. Nov18 CTN 50,7 Pro- CTN 0,57 CEA 1,8. Mar19 CTN 59,5 Pro- CTN 0,52 CEA 2,4. Nov19 CTN 80,7 Pro- CTN 0,66 CEA 2,4. Mar20 CTN 111 Pro- CTN 0,8 CEA 2,9. Normal Values: CTN < 2 pg/mL, Pro- CTN < 0,12 ng/mL, CEA < 0,1 ng/mL