Andrei Iagaru MD, Presenter: Nothing to Disclose

Rinat Masamed BA, Abstract Co-Author: Nothing to Disclose

Peter A. Singer MD, Abstract Co-Author: Nothing to Disclose

Peter Stephen Conti MD, PhD, Abstract Co-Author: Nothing to Disclose

FDG PET has an established role in restaging of various cancers, including papillary and undifferentiated thyroid carcinoma. However, controversies exist regarding its ability to reliably assess recurrent medullary thyroid cancer. We were therefore prompted to review our experience with FDG PET for detection of occult medullary thyroid cancer (MTC).

This is a retrospective study (Apr 1st, 1995 – Mar 31st, 2005) of 13 patients (pts) with histologic diagnosis of MTC, who had PET examinations. The group included 6 males and 7 females, with age range of 15-62 years (average: 48±13). The PET scan request was triggered by raising levels of calcitonin and negative anatomical imaging studies. Ten examinations were performed on a dedicated PET scanner, while the remaining three were acquired on a PET/CT unit.

Recurrent/metastatic disease was identified by PET in 7 (54%) of the 13 patients. The lesions were located in superior mediastinum (4), thyroid bed (2), cervical lymph nodes (3), lung (1) and liver (1). The calcitonin levels ranged from 52 to 5090 pg/ml (average: 1996 pg/ml) in patients with negative PET scans and from 132 to 9500 pg/ml (average: 3757 pg/ml) in patients with positive studies.

The published results of PET in detection of residual/recurrent MTC are contradictory. Our findings suggest a lower performance of PET in these patients, with a detection rate of 54%. However, all these patients had negative imaging studies prior to the PET scan, so FDG PET provides additional information in a significant fraction of cases (54%) and could be used for restaging of patients with MTC and elevated levels of biomarkers (calcitonin). Additional studies are necessary to further evaluate the role of FDG PET in medullary thyroid cancer.

FDG PET has an established role in restaging of various cancers, including papillary and undifferentiated thyroid carcinoma. However, controversies exist regarding its ability to reliably assess recurrent medullary thyroid cancer. We were therefore prompted to review our experience with FDG PET for detection of occult medullary thyroid cancer (MTC).

This is a retrospective study (Apr 1st, 1995 – Mar 31st, 2005) of 13 patients (pts) with histologic diagnosis of MTC, who had PET examinations. The group included 6 males and 7 females, with age range of 15-62 years (average: 48±13). The PET scan request was triggered by raising levels of calcitonin and negative anatomical imaging studies. Ten examinations were performed on a dedicated PET scanner, while the remaining three were acquired on a PET/CT unit.

Recurrent/metastatic disease was identified by PET in 7 (54%) of the 13 patients. The lesions were located in superior mediastinum (4), thyroid bed (2), cervical lymph nodes (3), lung (1) and liver (1). The calcitonin levels ranged from 52 to 5090 pg/ml (average: 1996 pg/ml) in patients with negative PET scans and from 132 to 9500 pg/ml (average: 3757 pg/ml) in patients with positive studies.

The published results of PET in detection of residual/recurrent MTC are contradictory. Our findings suggest a lower performance of PET in these patients, with a detection rate of 54%. However, all these patients had negative imaging studies prior to the PET scan, so FDG PET provides additional information in a significant fraction of cases (54%) and could be used for restaging of patients with MTC and elevated levels of biomarkers (calcitonin). Additional studies are necessary to further evaluate the role of FDG PET in medullary thyroid cancer.

Iagaru, A, Masamed, R, Singer, P, Conti, P, Detection of Occult Medullary Thyroid Cancer with FDG PET and PET/CT.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4413142.html