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10.1245/ASO.2004.10.015
Annals of Surgical Oncology 11:786-794 (2004)
© 2004 Society of Surgical Oncology
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ORIGINAL ARTICLES

Impact of 18F-Fluoro-2-Deoxy-D-Glucose Positron Emission Tomography (FDG-PET) in Patients with Biochemical Evidence of Recurrent or Residual Medullary Thyroid Cancer

J.W. B. de Groot, MD, Th.P. Links, MD, PhD, P.L. Jager, MD, PhD, T. Kahraman, MD and J.Th. M. Plukker, MD, PhD

From the Departments of Surgical Oncology (JWBdeG, TK, JThMP) and Endocrinology (ThPL) and the Nuclear Medicine/PET Center (PLJ), University Hospital, Groningen, The Netherlands.

Correspondence: Address correspondence and reprint requests to: J. Th. M. Plukker, MD, PhD, Department of Surgical Oncology, University Hospital Groningen, P.O. Box 30001, 9700 RB Groningen, the Netherlands; Fax: 31-50-3614873; E-mail: j.t.m.plukker{at}chir.azg.nl


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Background: Conventional imaging such as with 99mTc(V)dimercaptosunnic acid (DMSA), 111In-octreotide scintigraphy, computed tomography (CT), and magnetic resonance imaging (MRI) rarely localizes occult medullary thyroid cancer (MTC). The role of 18F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) is not well defined. The aim of this study was to examine the usefulness of postoperative FDG-PET in localizing MTC metastases.

Methods: FDG-PET was performed in 26 patients with elevated serum tumor markers after total thyroidectomy with central compartment dissection and additional neck dissection on indication. Patient- and lesion-based results were compared with the findings of conventional nuclear imaging and validated by morphological imaging (CT, MRI, ultrasonography), including bone scintigraphy and pathology when possible. Clinical impact was evaluated.

Results: FDG-PET detected foci in 50% of patients with lesion-based sensitivity of 96%. 111In-octreotide detected foci in 19% with sensitivity of 41%, and 99mTc(V)DMSA scintigraphy and morphological imaging detected foci in 21% and 40%, respectively, with sensitivity of 57% and 87%. No lesions were found in 11 patients (42%). Positive FDG-PET findings led to surgical intervention in nine patients (35%). They all underwent surgery for removal of residual tumor or metastases. One patient achieved disease-free status. In all patients who underwent surgery, serum calcitonin levels were reduced by an average of 58 ± 31%.

Conclusions: For detection of occult MTC lesions, FDG-PET is superior to conventional nuclear imaging and is the best detection method yet available. FDG-PET in postoperative follow-up has clinical value and may be used for guiding reoperation and additional morphological imaging preoperatively.

Key Words: FDG-PET • Medullary thyroid cancer • Metastases


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
PATIENTS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Medullary thyroid carcinoma (MTC) is a rare calcitonin- and carcinoembryonic antigen (CEA)–secreting tumor of the parafollicular C cells of the thyroid. It accounts for 3% to 10% of all thyroid malignancies.1–3 MTC occurs sporadically or is hereditary, with an autosomal dominant pattern of inheritance. In 35% of patients with MTC, cervical and mediastinal node metastases are already present at the time of initial diagnosis.4 Surgical resection of all the tumor manifestations still remains the only effective treatment with curative intent for these patients. The effect of radiotherapy is minimal and limited to a selected group of patients.3 The effect of chemotherapy remains disappointing, and it may induce severe toxicity.5,6

Recurrent or occult disease is a frequently encountered problem, particularly in patients with advanced primary tumors, even after adequately performed dissection. These cases are difficult to manage but are clinically the most relevant group, since correct localization of resectable disease can result in remission with local tumor control, and patients with distant metastases who will not benefit from extensive reoperation can be identified. Current detection methods commonly fail to identify residual or recurrent disease, despite elevated serum calcitonin levels. Standard employed conventional imaging methods such as scintigraphic examination with thallium-201 chloride (201Thallium), 131I-meta-iodobenzylguanidine (MIBG), pentavalent technetium-99m dimercaptosuccinic acid (99mTc[V]DMSA), and 111In-octreotide have limited sensitivity.7–17 Currently, 99mTc(V)DMSA scintigraphy seems to be the best imaging method. However the reported sensitivity varies between 33% and 95%.9,11–15,21 Positron emission tomography (PET) with 18F-fluoro-2-deoxy-D-glucose (FDG) as radiopharmaceutical tracer to investigate tumor metabolism has been used to visualize recurrent and metastatic MTC. The first results were promising, but these studies included small numbers of patients,18,19 patients with less extensive primary surgical treatment,20–22 or patients in whom a smaller area of the body was scanned.20

The aim of this study was to investigate the potential use of FDG-PET in the detection of minimal residual or recurrent MTC in patients with biochemical evidence of disease after total thyroidectomy with central compartment dissection and additional selective neck dissection on indication and to compare the findings with those by the traditional detection methods. In addition, since FDG-PET is not routinely used in patients with MTC, the clinical impact of the use of FDG-PET in the treatment of these patients is described.


   PATIENTS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 PATIENTS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Patients
All patients with histologically proven MTC with increased serum calcitonin or CEA levels after adequate initial surgical treatment were prospectively included after written informed consent and approval of the local medical ethics committee were obtained. Patients who presented with palpable lesions suspected to be recurrent tumors were not included. Data were gathered from January 1998 until February 2002 from 26 consecutive patients (15 men and 11 women). All these patients underwent a FDG-PET scan after initial total thyroidectomy with central compartment dissection and additional selective neck dissection on indication (unilateral, n = 14; bilateral, n = 4), after a median follow-up of 54 (range, 2–359) months. The median age was 50.5 years (range, 15–75). All patients had elevated serum calcitonin levels (mean, 8582 ng/L; range, 7–85,000 ng/L). CEA levels were abnormal in 20 patients (77%), with values between 5 µg/L and 2265 µg/L. The population consisted of 14 patients with sporadic MTC, 11 with multiple endocrine neoplasia (MEN) syndrome 2A, and 1 with MEN 2B. Clinical characteristics of the individual patients are listed in Table 1.


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  		TABLE 1. Clinical characteristics of the study population
 
METHODS
Basal serum calcitonin levels (reference level, <50 ng/L) were measured by 125I radioimmunoassay (Nichols Institute Diagnostics, San Clemente, CA) until November 2000; from that time until May 2001, they were measured by an enzyme-linked immunosorbent assay from Biosource Europe SA (Nivelles, Belgium; reference level, <5 ng/L). From May 2001 until January 2002 the levels were measured by an enzyme-linked immunosorbent assay from Sangui Biotech, Inc. (Santa Ana, CA; reference level, <12 ng/L). CEA value (reference level, <4.5 µg/L) was determined by luminometry. Depending on the preference of the treating physician, patients with MTC and elevated serum calcitonin and/or CEA levels underwent at least two other imaging procedures besides FDG-PET. In our hospital, MRI of the neck is performed instead of ultrasound examination. 99mTc(V)DMSA scintigraphy was performed on 25 patients; for 1 patient, 99mTc(V)DMSA scintigraphy was performed more than 18 months prior to FDG-PET, and therefore the results were not included. 111In-octreotide scintigraphy was performed on 21 patients, MRI or CT of the neck and mediastinum was performed on 25 patients, CT of the lungs and CT and/or ultrasonography of the abdomen were performed on all patients, and bone scintigraphy and/or MRI of a bone lesion was performed on 17 patients. In this study FDG-PET was performed additionally. All diagnostic imaging examinations of the same patient were completed within an 18-month interval and were performed at least 2 months after any therapy. The results were confirmed by histology when possible. Clinical interventions based on the result of FDG-PET were documented.

Imaging Protocol
FDG-PET
All patients were studied after a 6-hour fast. Data acquisition started about 90 minutes after injection of 400 MBq FDG intravenously. An ECAT 951/31 or an ECAT HR+ positron camera (Siemens/CTI, Knoxville, USA) was used for data acquisition. The 951/31 device has a 56-cm diameter patient aperture and acquires 31 planes simultaneously over a 10.8-cm axial field of view. The HR+ camera has a 56-cm diameter patient aperture and acquires 63 planes simultaneously over a 15.8-cm axial field of view. System spatial resolution was 5–7 mm FWHM (for reconstructed transaxial images). Scanning was performed from the level of the femur to the head (crown). Emission (5 minutes/bed position) and transmission scans (2 minutes/bed position) were performed alternately with the same positions. Total scanning time (emission and transmission scans) was approximately 60 minutes. An iterative reconstruction method was used. The whole-body scans were displayed in both projection and volume views, the latter with coronal, sagittal, and transaxial views.

111In-octreotide and 99mTc(V)DMSA Scintigraphy
Patients were injected with 200-MBq 111In-octreotide (Mallinckrodt, Petten, The Netherlands), and 24 to 48 hours after injection, whole-body and (when indicated) SPECT images were acquired with a Multispect 2 (Siemens, Hoffmann Estates, IL) double-headed gamma camera equipped with a medium energy collimator. For 99mTc(V)DMSA scintigraphy we used 500 MBq and an injection-image interval of 2 hours.

Morphological Imaging
Morphological imaging was performed with standard protocols. CT scanning was performed with a Tomoscan SR 7000 scanner (Philips, Eindhoven, The Netherlands). A slice thickness of 5 mm was used from the base of the scull to the apex of the lung. For the rest of the body we used a slice thickness of 10 mm.

MRI was performed with a 1.5T Magneton permanent magnetic system (Siemens Medical Systems, Erlangen, Germany) with gadolinium to improve resolution. MRI was performed with a body coil in the supine position. Sagittal, horizontal, and coronal images were obtained with two different pulse sequences: T2-weighted images and short T1 inversion recovery images.

Interpretation of the Data
Two experienced readers from a group of three (with consensus reading by the third) independently interpreted the images on an image display. The FDG-PET scans were scored without knowledge of the outcome of other imaging data. The readers were aware of the elevated serum calcitonin levels after primary surgical treatment for MTC.

When both independent observers reported higher uptake of FDG than in the surrounding normal tissue that could not be explained physiologically or by another explanation, the finding was considered pathological. Differences were resolved by consensus reading. The regions of metastasis or recurrence were divided into four areas: regional, lung, liver, and bone. Two other investigators blinded for the FDG-PET results scored 111In-octreotide and 99mTc(V)DMSA images similarly. Lymph nodes of >1 cm in short diameter, detected by morphological imaging, were considered pathological. All FDG-PET findings were compared with other performed staging techniques such as 111In-octreotide and 99mTc(V)DMSA scintigraphy and morphological imaging (including bone scintigraphy).

Because not all lesions could be histologically validated, we used noninvasive imaging techniques to confirm the lesions in these cases. Bone metastases were confirmed with bone scintigraphy or MRI, and lung, cervical, and mediastinal metastases were confirmed with CT and/or MRI. Lesions that were detected with either FDG-PET, 111In-octreotide, or 99mTc(V)DMSA scintigraphy and validated morphologically or with bone scintigraphy had to be visible in at least two consecutive morphological scans or with at least two different imaging methods. Sensitivity and specificity of the individual procedures were analyzed on a per-patient basis and a localization basis.

By means of {chi}2 analysis, FDG-PET findings were compared with those from 99mTc(V)DMSA and 111In-octreotide scintigraphy and with those from morphological imaging, including bone scintigraphy. Two-sided P values < .05 were considered significant.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
For 17 of the 26 patients (65%), both readers independently reached the same conclusion in interpreting the FDG-PET scans. For the remaining nine patients, differences were resolved by consensus reading, and all concerned cases with weakly positive or negative primary tumor uptake.

There were no instances in which there was no agreement among the three readers.

Patient-Based Analysis
In 5 of 24 patients (21%), positive foci were seen with 99mTc(V)DMSA scintigraphy. 111In-octreotide scintigraphy showed hot spots in 4 of 21 patients (19%). Morphological imaging (CT, MRI, or ultrasound) in combination with bone scintigraphy revealed lesions in 10 patients (40%). Suspected lesions were identified in 13 of the 26 patients (50%) examined by FDG-PET. Figures 1 and 2 show examples of true-positive metastases in patients with morphologically and histologically proven metastases detected with FDG-PET (Fig. 2).



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  		FIG. 1. FDG-PET whole-body projection image of patient 17 showing multiple lesions in the neck, liver, and pelvic bone (arrows), all confirmed to be metastases of medullary thyroid cancer.

 


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  		FIG. 2. Normal 99mTc(V)DMSA planar image (left) and abnormal FDG-PET projection image (right) in patient 11. FDG-PET shows subtle asymmetry with increased uptake in the right neck (arrow), histologically confirmed to be a metastasis.

 
In 11 patients (42%), all imaging techniques failed to depict lesions, despite the elevated calcitonin levels in all patients. Elevated CEA levels ranging from 5 to 31 µg/L were found in all but four patients (patients 2, 6, 13, and 23) with CEA levels of <4 µg/L. In all these patients, the results of FDG-PET, 99mTc(V)DMSA scintigraphy, 111In-octreotide scintigraphy, morphological imaging, and bone scintigraphy were considered false-negative.

The patient-based analysis of our data demonstrated a sensitivity of 41% for FDG-PET, 17% for 99mTc(V)DMSA scintigraphy, 14% for 111In-octreotide scintigraphy, and 30% for morphological imaging in combination with bone scintigraphy. Positive predictive values for FDG-PET, 99mTc(V)DMSA scintigraphy, 111In-octreotide scintigraphy, and morphological imaging in combination with bone scintigraphy were 82%, 80%, 75%, and 67%, respectively. Negative predictive values could not be determined, since all patients had biochemical evidence of MTC, and consequently there were no true-negative patients.

Detailed Lesion Analysis
A total of 130 lesions were detected by FDG-PET, 99mTc(V)DMSA scintigraphy, 111In-octreotide scintigraphy, bone scintigraphy, and morphological imaging. Histological validation was obtained for 32 lesions in 13 patients. In 27 lesions the results of the functional imaging could be confirmed by histology. These lesions were considered true-positives. In five lesions no malignancy was found; these lesions were considered false-positives. In one patient (patient 14) the positive findings were due to sarcoidosis; in the other patients (patients 4, 6, and 10), histology revealed osteoid osteoma, postradiation inflammation, and normal thymus tissue, respectively. The results of the detailed lesion analysis are shown in Table 2.


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  		TABLE 2. Results of detailed lesion analysis for all localizations
 
Of the nuclear imaging methods investigated, FDG-PET detected the highest number of lesions (n = 53), followed by 99mTc(V)DMSA scintigraphy (n = 26) and 111In-octreotide scintigraphy (n = 12). Morphological imaging procedures and bone scintigraphy detected 38 lesions. On average, 99mTc(V)DMSA scintigraphy detected 1 lesion per patient; 111In-octreotide scintigraphy, 0.5 per patient; FDG-PET, 2.1 per patient; and morphological imaging with bone scintigraphy, 1.5 per patient. There is a significant difference (P < .05) between conventional nuclear imaging methods (99mTc[V]DMSA scintigraphy, 111In-octreotide scintigraphy), morphological imaging (CT, MRI, ultrasonography) in combination with bone scintigraphy, and FDG-PET. Of these four imaging methods, FDG-PET shows the most lesions. Table 3 illustrates the relationship between FDG-PET, 99mTc(V)DMSA, and 111In-octreotide scintigraphy and morphological imaging including bone scintigraphy. FDG-PET depicted nine previously unknown lesions in seven patients. Lymph node metastases were found in all patients. In three patients, no histological validation was obtained. Two patients had disseminated disease and did not undergo surgery, and one patient declined surgery. In the remaining four patients, the FDG-PET results were histologically validated. In patient 10 the lesion proved to be benign.


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  		TABLE 3. Relationship between the different imaging procedures on a patient basis and on a lesion basis
 
The lesion-based analysis of our data demonstrated a sensitivity of 96% for FDG-PET, 57% for 99mTc(V)DMSA scintigraphy, 41% for 111In-octreotide scintigraphy, and 87% for morphological imaging in combination with bone scintigraphy. Positive predictive values for FDG-PET, 99mTc(V)DMSA scintigraphy, 111In-octreotide scintigraphy, and morphological imaging including bone scintigraphy were 96%, 92%, 92%, and 89%, respectively. Negative predictive values were 67%, 18%, 16%, and 38%, respectively.

Clinical Impact
Figure 3 shows the clinical findings in respect to FDG-PET for all patients. In patients with a negative FDG-PET scan no MTC was detected by any imaging procedure.



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  		FIG. 3. Analysis of the clinical consequences of FDG-PET and validation of the FDG-PET results with morphological imaging, including bone scintigraphy; histology; or persistently elevated tumor markers on long-term follow-up.

 
Positive FDG-PET findings lead to surgical intervention in nine patients (Table 4). All nine patients underwent surgery for removal of residual tumor or metastases, and MTC was histologically confirmed in eight. One patient (patient 22) achieved disease-free status after repeated unilateral selective neck dissection with a follow-up interval of 24 months. In one patient (patient 10), histology revealed normal thymus tissue without MTC. In all patients serum calcitonin levels were reduced by an average of 58 ± 31% after surgery. Postoperative serum calcitonin values were not determined in one patient (patient 8) because of technical factors. This patient died of a non-MTC-related cause before another sample could be collected. The 11 patients in whom no metastases were found continued to be carefully followed-up. At the time of writing, regardless of the imaging procedures used, they were alive or had died (one patient, of cerebrovascular accident) without detectable metastases.


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  		TABLE 4. Results of re-operation due to positive FDG-PET findings
 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
This study shows that FDG-PET is superior to conventional 99mTc(V)DMSA and 111In-octreotide scintigraphy and morphological imaging in combination with bone scintigraphy for detecting occult MTC lesions. FDG-PET appears to be valuable in the follow-up of MTC, since extra lesions were detected by methods in addition to conventional imaging in seven of the 26 patients (27%). FDG-PET led to surgical intervention in 35% of our study population, and in seven patients (27%) these interventions were with curative intent. This resulted in complete remission in one patient and a substantial decline in serum calcitonin levels in the other patients. Early identification and treatment of recurrent or persistent tumor are useful because reoperation for residual MTC may prevent local symptoms or distant metastases, even in patients who cannot be cured.23 In patients with metastatic disease, locoregional control may prevent airway obstruction or invasion into great vessels.24 Although patients with persistent hypercalcitoninemia after apparent curative primary surgery may have a 10-year survival up to 86%,25 these findings point out the clinical relevance of FDG-PET.

According to our data, the use of conventional nuclear imaging in patients with occult MTC is hard to justify, since the results of these methods are disappointing and FDG-PET can replace these conventional diagnostic tools, probably with comparable costs. Furthermore, our results indicate that in cases of negative FDG-PET, subsequent morphological imaging has limited additional value, since it was positive in only two patients and even these detected lesions proved to be false-positive. Morphological examination can be performed when there is clinical evidence of recurrent MTC, for better anatomical localization and determination of the extent of disease. When FDG-PET shows regional hot spots with negative morphological imaging, surgical intervention could be still a good option. We would recommend morphological imaging in FDG-PET-positive cases to guide therapeutic actions.

Compared with 99mTc(V)DMSA and 111In-octreotide, FDG-PET detected more lymph node and organ metastases. This corresponds with previous findings.22,26 Compared with morphological imaging in combination with bone scintigraphy, FDG-PET detected equal numbers of lymph node metastases and metastases to liver and lung but more bone metastases. These findings are in keeping with the findings of Nakamoto et al.27 The reported sensitivity of 99mTc(V)DMSA scintigraphy varies between 33% and 95%,9,11–15,21 which agrees with the findings on a lesion basis in the present study. The uptake mechanism of 99mTc(V)DMSA in tumor cells, however, is still not clear. More specific radiopharmacons, such as the somatostatin analogue 111In-octreotide, have low reported sensitivities of 25% to 34%.14–17,26 In a lesion-based analysis we found sensitivity of 41%, and in a patient-based analysis sensitivity was 14% with 111In-octreotide scintigraphy. The relatively low number of lesions detected with 111In-octreotide scintigraphy could be explained by the assumption that the number of somatostatin receptors with high affinity for octreotide in MTC is insufficient. It is known that 111In-octreotide has high affinity only for the somatostatin receptor subtype II and has affinity to a lesser extent to the somatostatin receptor subtypes III and V.17 Furthermore, in vitro studies have shown that only about 40% of MTCs express these receptors.28

On the basis of the results of functional imaging, we performed morphological imaging to validate identified lesions suitable for surgery. We believe that FDG-PET can lead to improved detection of MTC by guiding morphological imaging with better interpretation of the results. Wang et al.29 reported a sensitivity of 74% and a specificity of 98% in detecting primary MTC and regional metastasis to the lymph nodes with MRI, but without previous functional imaging procedures. Diehl et al.21 reported a pooled sensitivity of CT and MRI of 67%. On a lesion basis, we noted higher sensitivity with morphological imaging in combination with bone scintigraphy. Morphological imaging procedures like MRI and CT appear to be sensitive for large lesions, usually larger than 1 cm.30,31 Although MRI has a reported sensitivity of 74% to 98% and specificity of 67% to 98%,21,29 it relies on morphological differences between normal tissue and metastases. Benign lesions cannot be reliably differentiated from malignant changes on the basis of morphology, and the uptake of contrast medium and small lesions often are not detected; therefore, true specificity is most likely not very high.

The sensitivities of the methods used in this study have often been determined by comparison with morphological imaging, which obviously has some limitations. We tried to minimize this data bias by comparing functional imaging methods with multiple consecutive morphological scans and by adding bone scintigraphy in several cases. However, since histologic data could not be obtained for 50% of the patients, tumor lesions that did not take up any of the radiopharmacons used and were smaller than 1 cm in diameter could still have been missed.

Since cervical and mediastinal lymph nodes are the first to be involved in metastatic MTC, the number of lymph node metastases in patients participating in this study is relatively low. In respect to the populations in other studies,18–22 primary surgery in our study group was extensive, including total thyroidectomy with central compartment dissection and additional selective neck dissection on indication. This could be a plausible explanation for the observed low numbers of node metastases after the initial surgical procedure, especially since the numbers of metastases at sites beyond the influence of the surgeons’ skills in this study and in each of the reports involving a substantial number of patients were even higher (Table 5).


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  		TABLE 5. Number of organ metastases detected with FDG-PET in patients with MTC
 
Despite all efforts, almost half of our patients showed no pathological uptake of any of the radiopharmacons used, and MTC lesions did not meet the morphological criteria for malignancy as well. A weakness of FDG-PET in the diagnosis and follow-up of MTC is the slow growth rate and low proliferation index of neuroendocrine tumors, resulting in usually normal glucose metabolism.26,32 This may explain the inability to detect small foci of MTC with FDG-PET in patients with only biochemical evidence of disease. If all the limitations of the different detecting procedures are considered, it seems that the lesions responsible for elevated serum calcitonin and CEA levels are to small to be identified with current imaging methods. In a study performed by Tung et al.,33 laparoscopic liver examination revealed metastases that were not detected by CT or MRI in 22% of patients. Musholt et al.19 reported five liver metastases in one patient that were not detected by FDG-PET, and Ésik et al.34 reported an 89% prevalence of multiple small hypervascular hepatic metastases that were not detected by CT, MRI, and FDG-PET in patients with elevated serum calcitonin levels. Although laparoscopic inspection of the liver appears to be more sensitive than FDG-PET in identifying small metastatic foci in patients with negative functional and morphological imaging, it remains an invasive detection method associated with additional morbidity in these relatively difficult, manageable small lesions.31,32

Our data indicate that FDG-PET is the most feasible noninvasive method yet available for detection of recurrent or residual disease in the follow-up of MTC. FDG-PET is a better detection method than 99mTc(V)DMSA and 111In-octreotide and can guide direct diagnostic and therapeutic actions. However, FDG-PET may still be false-positive, since FDG is also accumulated in inflammation, leading to unnecessary surgery.35 Therefore, we still need additional information acquired through CT or MRI.

Although FDG-PET plays a role in detecting foci of MTC in patients with biochemical evidence of disease, the encouraging results are still far from optimal. Using other radiopharmacons like F-DOPA-PET may yield even better results than FDG-PET. The first report is promising,26 but further research needs to be performed.

In conclusion, we recommend FDG-PET in patients with postoperative elevated serum calcitonin and CEA levels in order to detect foci of residual or recurrent MTC and to select those patients who might benefit from reoperation with curative intent. FDG-PET in the postoperative follow-up has clinical value and may be used for guiding reoperation and additional morphological imaging preoperatively.


   FOOTNOTES
 
FDG-PET is superior to conventional nuclear imaging and is the best noninvasive method available to detect foci of residual MTC in patients with postoperative elevated serum calcitonin and carcinoembryonic antigen levels. FDG-PET can help select patients who might benefit from reoperation.

Received for publication October 15, 2003. Accepted for publication April 27, 2004.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

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