PET/CT imaging of thyroid cancer

Positron emission tomography (PET) is a highly sensitive, low invasive technology for cancer biology imaging. The role of F-18 FDG PET/CT in differentiated thyroid cancer (DTC) is well established, particularly in patients presenting with elevated Tg levels and negative radioactive iodine WBS. It has been demonstrated that F-18 FDG uptake represents less differentiated thyroid cancer cells or dedifferentiated cells and PET positive lesions are more likely to be resistant to I treatment. The uptake of F-18 FDG is related to tumor size, thyroid capsule invasion and histological variants with a poor prognosis. As in other cancers, early detection of recurrences improves outcomes and survival. I PET/CT can also be used to image the patients with DTC, similarly to I WBS. Compared with F-18 FDG PET/CT, its spatial resolution is only slightly degraded but increasing the imaging time reduces this difference. In addition, F-18 FDG PET/CT has been found helpful in the management of patients with anaplastic and medullary thyroid cancer. Other radiopharmaceuticals such as Ga-DOTATOC and F-18 DOPA may provide complimentary information to F-18 FDG PET/CT in the detection of recurrent thyroid cancer.     

Transiently Altered Distribution of F-18 FDG in a Patient with Subacute Thyroiditis

F-18 fluorodeoxyglucose (FDG) is a highly influential radiotracer that provides valuable information in many cancer types. However, the normal biodistribution of F-18 FDG is often variable and can be altered by intrinsic or iatrogenic factors. We report a case of diffuse symmetrically increased skeletal muscle uptake and relatively decreased hepatic uptake on F-18 FDG PET/CT in a 57-year-old female with pulmonary adenocarcinoma. Detailed clinical evaluation and retrospective radiologic evaluation revealed that she had been diagnosed with subacute thyroiditis 2 weeks ago. After 6 weeks, F-18 FDG distribution was normalized at the follow-up PET/CT study.     

Unexpected Second Primary Malignancies Detected by F-18 FDG PET/CT During Follow-up for Primary Malignancy: Two Case Reports

As the survival rate of cancer patients has increased over the last few decades, the risk of cancer survivors developing second primary malignancies has gained attention. We report two rare cases of second primary hematologic malignancy detected by ¹⁸F-fluorodeoxyglucose (F-18 FDG) positron emission tomography/computed tomography (PET/CT) during follow-up for primary solid malignancies. Acute lymphoblastic leukemia developed in a breast cancer patient and non-Hodgkin lymphoma in an anal cancer patient. F-18 FDG PET/CT findings led to the diagnosis of unexpected second primary hematologic malignancy in cancer survivors in these two cases.     

F-18 FDG PET/CT imaging of metastatic extrarenal Wilms tumor arising in the inguinal canal

Extrarenal Wilms tumor (ERWT) is rare, and has been reported sporadically in the literatures. ERWT can arise anywhere from the renal bed to the testes; reported locations of ERWTs include the retroperitoneum, inguinal canal, endocervix, uterus, epididymis, and sigmoid mesocolon. We report the F-18 FDG PET/CT imaging findings of an ERWT arising from the inguinal canal in a 9-year-old boy. F-18 FDG accumulated in the metastatic lesions of the lung and mediastinal lymph nodes, as well as the primary ERWT. After chemotherapy, a follow-up PET/CT showed complete metabolic remission. F-18 FDG PET/CT is useful in detecting primary and metastatic ERWTs and in evaluating treatment response.     

A Case of Urethral Metastasis from Sigmoid Colon Cancer Diagnostically and Prognostically Indicated by F-18 FDG PET/CT

Urethral metastasis from colorectal cancer is rare and is known to have a poor prognosis. A 72-year-old man with a history of colectomy and colostomy due to sigmoid colon cancer was admitted to the emergency room with bowel distension, rectal bleeding and urinary symptoms. Computed tomography of the abdominopelvis showed sigmoid colon cancer with multiple metastases involving the liver. Positron emission tomography with F-18 fluorodeoxyglucose (FDG) showed multiple hypermetabolic foci in the liver, penis and pubic bone, which otherwise could not be diagnosed. The lesions revealed no improvement with chemotherapy and urological surgery on follow-up F-18 FDG PET/CT. We present a case of urethral metastasis of sigmoid colon cancer diagnostically and prognostically indicated by F-18 FDG PET/CT.     

Abdominal Mesh Implant Showing FDG Uptake on PET/CT

F-18 fluorodeoxyglucose (FDG) uptake by a mesh implant might be caused by a foreign body granulomatous reaction with inflammation and fibrosis, which can be demonstrated by positron emission tomography/computed tomography (PET/CT). A 71-year-old man underwent F-18 FDG PET/CT for the follow-up evaluation after an operation for colonic adenocarcinoma. On PET/CT imaging, there was a rectangular-shaped FDG uptake (maximal standardized uptake value, maxSUV: 3.4) in the anterior abdominal wall. On the review of the medical records, the patient had a history of herniorrhapy for the reinforcement of the abdominal wall 2 months previously, using a mesh implant consisting of polytetrafluoroethylene (Teflon). We report a case of FDG uptake associated with surgical procedures including mesh implant on F-18 FDG PET/CT.     

Bone metastasis in patients with non-small cell lung cancer: The diagnostic role of F-18 FDG PET/CT

Purpose

To evaluate the performance of F-18 FDG PET/CT in the detection of bone metastasis in non-small cell lung cancer (NSCLC) patients.

Materials and methods

Three hundred and sixty-two consecutive NSCLC patients who underwent F-18 FDG PET/CT scanning were retrospectively analyzed. Each image of PET/CT, combined CT, and PET was performed at 10 separate areas and interpreted blindly and separately. The sensitivity, specificity and accuracy of F-18 FDG PET/CT, combined CT and F-18 FDG PET were calculated and the results were statistically analyzed.

Results

Bone metastasis was confirmed in 82 patients with 331 positive segments based on the image findings and clinical follow-up. On patient-based analysis, the sensitivity of F-18 FDG PET/CT (93.9%) was significantly higher than those of combined CT (74.4%) and F-18 FDG PET (84.1%), respectively (p < 0.05). The overall specificity and accuracy of combined CT, F-18 FDG PET, and F-18 FDG PET/CT were 90.7%, 93.2%, 98.9% and 87.0%, 91.2%, and 97.8%, respectively (compared with PET/CT, p < 0.05). On segment-based analysis, the sensitivity of the three modalities were 79.5%, 94.3%, and 98.8%, respectively (compared with PET/CT, p < 0.05). The overall specificity and accuracy of the three modalities were 87.9%, 89.2%, 98.6% and 84.5%, 91.2%, 98.7%, respectively (compared with PET/CT, p < 0.05).

Conclusion

F-18 FDG PET/CT is superior to F-18 FDG PET or combined CT in detecting bone metastasis of NSCLC patients because of the complementation of CT and PET. It is worth noting that the added value of F-18 FDG PET/CT may beneficially impact the clinical management of NSCLC.     

Impact of PET/CT in comparison with same day contrast enhanced CT in breast cancer management

PURPOSE: To evaluate the impact of F-18 fluorodeoxyglucose (FDG) positron emission tomography with fused computerized tomography (PET/CT) in comparison with same day contrast enhanced CT (CE-CT) in breast cancer management. METHOD: Seventy studies in 49 breast cancer patients, 17 for initial and 53 for restaging disease were included. All patients underwent PET/CT for diagnostic purposes followed by CE-CT scans of selected body regions. PET/CT was started approximately 90 minutes following IV injection of 10-15 mCi of F-18 FDG on a GE Discovery PET/CT system. Oral contrast was given before F-18 FDG injection. The CE-CT was performed according to departmental protocol. RESULTS: Out of a total of 257 lesions, 210 were concordant between PET/CT and CE-CT. There were 47 discordant lesions, which were verified by either biopsy (35) or follow-up (12 PET positive CE-CT negative lesions). PET/CT correctly identified 25 true positive (TP). CE-CT identified 2 TP lesions missed by PET/CT which were false negatives (FNs): one liver metastasis with necrosis, which was nonavid to FDG uptake because of necrosis and a second one missed on abdominal metastatic node, which did not change staging or treatment. PET/CT incorrectly identified 2 false positive lesions while CE-CT incorrectly identified 18 false positive. TP recurrence of the disease was found by PET/CT in 44% (15/34 pts), whereas 56% (19/34 pts) were free of disease. The CE-CT described progression of the disease in 1 true negative PET/CT study and no progression in 2 TP PET/CT studies. The sensitivity, specificity, accuracy, positive productive value, and negative productive value for PET/CT were 97.8%, 93.5%, 97.3%, 99.1%, 85% and for CE-CT were 87.6%, 42%, 82.1%, 91.6%, 31.7%. CONCLUSION: In this study, PET/CT played a more important role than CE-CT scans alone and provided an impact on the management of breast cancer patients.     

Incidental Finding of Appendiceal Adenocarcinoma in F-18 FDG PET/CT for Health Screening

F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) that simultaneously offers anatomic and metabolic information is widely used and has become an effective modality in many clinical fields, especially oncology, and also may detect an unexpected primary cancer. Appendiceal carcinoma is relatively uncommon and not associated with characteristic symptoms. We report the case of a 53-year-old man with appendiceal adenocarcinoma, who had only mild fever. The tumor was detected early on F-18 FDG PET/CT for health screening.     

Incidental Detection of Peri-Renal Hemorrhage on F-18 FDG PET/CT Imaging in a Patient with Polycystic Kidney Disease

A 72-year-old male patient with a history of polycystic kidney disease and lung malignancy underwent F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) for the evaluation of tumor recurrence. The FDG PET/CT and subsequent non-enhanced CT scans revealed a hemorrhage in the peri-renal space of the left original kidney. Interesting in this case was the incidental detection of unexpected peri-renal hemorrhage during an oncologic assessment with FDG PET/CT.     

Growing Cardiac Hemangioma on Serial F-18 FDG PET/CT

Cardiac hemangiomas are extremely rare, benign tumors, which can occur anywhere in the heart. Symptoms are variable according to the size, extension and tumor location, but most cases are asymptomatic and are detected incidentally. They may grow, remain stable and regress; therefore, the natural course of the tumors is unpredictable. Diagnosis mainly depends upon echocardiography, CT, MRI and angiography. Reports of detection by F-18 FDG PET/CT are very limited. We report a case of cardiac hemangioma attached to the right ventricle, compressing the ventricle. It was revealed incidentally on F-18 FDG PET/CT for routine evaluation of thyroid cancer. During two serial F-18 FDG PET/CTs, it grew from 2.8 cm to 4.0 cm with mild FDG uptake. After surgery, the patient remained stable without any complications.     

Collision lung cancer on F-18 FDG PET/CT

We report a case of a primary collision lung cancer consisting of squamous cell carcinoma and adenocarcinoma. A 73-year-old man with an abnormality found on chest radiograph in the right lower lobe was examined by FDG PET/CT (F-18 fluorodeoxyglucose positron emission tomography/computed tomography). The tumor was composed of 2 different morphologic and FDG accumulation portions and a collision tumor was suspected. Histopathologically, this tumor was composed of squamous cell carcinoma and adenocarcinoma. Each element was clearly distinguished but touched. FDG PET/CT is a useful tool to diagnose collision tumor as it shows morphologic and metabolic differences between 2 distinct tumor components.     

F-18 FDG PET demonstration of a thyroid metastasis in a patient with colon cancer

A 51-year-old man with a history of surgical removal of sigmoid colon cancer underwent F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) to search for distant metastases and/or local recurrence because the carcinoembryonic antigen level was elevated. F-18 FDG PET images showed increased focal FDG uptake in the left lobe of the thyroid. Computed tomography images showed thyroid tumor in the left lobe as well as F-18 FDG PET images. Thereafter he underwent thyroidectomy and the resected specimen was histopathlogically shown to have thyroid metastasis from colon cancer. F-18 FDG PET was useful to detect thyroid metastasis from colon cancer as well as the most frequently seen metastatic sites such as liver, lungs, and lymph nodes.     

Extraordinarily high F-18 FDG uptake caused by radiation necrosis in a patient with nasopharyngeal carcinoma

A false-positive F-18 FDG PET scan caused by osteoradionecrosis and inflammation in patients with nasopharyngeal carcinoma (NPC) has been reported. The standard uptake values (SUVs) in these false-positive cases are always below 6 and decrease with time. This report is concerned with a false-positive result with extraordinarily high F-18 FDG uptake, which increased on the delayed 3-hour image. A 63-year-old man with NPC underwent surgical removal and radiotherapy (7400 cGy) in July 2003. In October 2003, the CT scan showed a large soft tissue mass over the nasopharynx. Tumor recurrence was suspected. F-18 FDG PET scan showed an FDG-avid lesion over the nasopharyngeal region with a maximum SUV of 28.8 at 1 hour that increased to 30.4 at 3 hours. Biopsy was performed and the histopathologic examination showed only necrotic tissue and no evidence of tumor cells. Radiation necrosis was diagnosed. No evidence of tumor recurrence was noted during the 10-month follow-up period.     

F-18 FDG PET in insular thyroid cancer

PURPOSE: Insular thyroid cancer (ITC) is known to be a rare subtype of follicular thyroid carcinoma showing poor differentiation and an unfavorable prognosis. The authors evaluated the use of F-18-fluorodeoxyglucose (FDG) positron emission tomography (PET) for restaging and follow-up in ITC. METHODS: Five patients (2 male, 3 female) with elevated thyroglobulin levels (mean, 86 ng/mL; range 1.3-180 ng/mL) during follow-up underwent FDG PET (Siemens ECAT Exact 47). PET results were correlated to histopathologic and radiologic findings as well as to the results of whole-body radioiodine scintigraphy. In 1 patient a series of 4 PET scans was done. RESULTS: FDG PET showed a total of 10 tumor sites, at least 1 in each patient. Four of those lesions were detected by computed tomography (CT) as well, which in addition revealed 3 lesions that had normal glucose consumption. Five PET lesions were missed by the CT scan because they were found outside the examined volume of CT. Only 1 PET-positive lesion was also radioiodine positive. Three radioiodine-positive lesions with normal glucose metabolism were detected. CONCLUSION: As known for well and poorly differentiated thyroid cancer of the follicular epithelium, ITC may also show discordance between radioiodine studies and FDG-positive lesions. Given their initially poor differentiation, the ITC clearly showed the expected dominance of less well-differentiated, FDG-positive lesions. Therefore, FDG PET seems to be a very useful tool for the staging and restaging of such tumors.     

F-18 FDG PET/CT in the management of thyroid cancer

PURPOSE: There are approximately 32,000 new cases of thyroid carcinoma annually in the United States. F-18 FDG PET/CT has an established role in cancer management, including thyroid cancer, usually in patients who are thyroglobulin (Tg) positive/iodine negative. We reviewed our experience with F-18 FDG PET/CT in thyroid cancer, with an emphasis on correlation with Tg, and maximum standardized uptake values (SUV). We also analyzed the role of thyroid stimulating hormone (TSH) on PET/CT results. MATERIALS AND METHODS: This is a retrospective study (January 2003 to December 2006) of 76 patients with differentiated thyroid cancer, who had F-18 FDG PET/CT scans. There were 44 women and 32 men, with age range of 20 to 81 years (average, 51.1 +/- 18.1). The administered doses of F-18 FDG ranged from 396 to 717 MBq (15.8-19.4 mCi) (average, 566 +/- 74.8) (15.3 +/- 2). Reinterpretation of the imaging studies for accuracy and data analysis from medical records were performed. RESULTS: A total of 98 PET/CT scans were analyzed (59 patients had 1 scan, 12 patients had 2, and 5 patients had 3). PET/CT was 88.6% sensitive (95% CI: 78.-94.3) and 89.3% specific (95% CI: 71.9-97.1). Mean Tg level was 1203 ng/mL (range, 0.5-28,357) in patients with positive PET/CT and 9.72 ng/mL (range, 0.5-123.0) in patients with negative PET/CT scans (P = 0.0389). Mean SUV max was 10.8 (range, 2.5-32) in the thyroid bed recurrence/residual disease and 7.53 (range, 2.5-26.2) in metastatic lesions (P = 0.0114). Mean SUV max in recurrent/residual disease in patients with TSH 30 mIU/L was 8.1 (range, 2.6-32) (P = 0.2994). CONCLUSION: F-18 FDG PET/CT had excellent sensitivity (88.6%) and specificity (89.3%) in this patient population. Metastatic lesions were reliably identified, but were less F-18 FDG avid than recurrence/residual disease in the thyroid bed. TSH levels at the time of PET/CT did not appear to impact the FDG uptake in the lesions or the ability to detect disease. In the setting of high or rising levels of Tg, our study confirms that it is indicated to include PET/CT in the management of patients with differentiated thyroid cancer.     

¹¹C-choline and F-18 FDG PET/CT images of hemangioblastoma

We present the F-18 FDG and 11C-choline PET/CT images obtained in 2 cases of hemangioblastoma. Hemangioblastoma is a highly vascular benign tumor that typically arises in the cerebellum or spine. The characteristic findings of a hemangioblastoma on both CT and MR include a peripherally located cerebellar lesion with a central cystic region and a peripherally enhanced nodule. In both patients, the uptake in the lesion was relatively low on the F-18 FDG PET/CT images and relatively high on the 11C-choline PET/CT images.     

F-18 FDG PET/CT in rectal carcinoma: where are we now?

This short review aims at summarizing the available data pertaining to the usefulness of F-18 FDG PET/CT in rectal cancer. It is specifically focused on the emerging role of F-18 FDG PET/CT in assessing the response to neoadjuvant combined radiochemotherapy in locally advanced rectal cancer. It also probes the possibility of finding standardized PET/CT parameters that are capable of differentiating responders from nonresponders in whom therapeutic approach could be modified.     

Malignant extrarenal rhabdoid tumor of the spine: staging and evaluation of response to therapy with F-18 FDG PET/CT

Malignant extrarenal rhabdoid tumor (ERRT) is a very rare type of soft-tissue sarcoma with a reported incidence of 0.3% of all soft-tissue sarcomas. Only 7 cases of spinal malignant ERRT have been reported in the literature, and to our knowledge, F-18 FDG PET/CT imaging for staging and evaluation of response to therapy for these tumors has not been previously described. This is a case of an 8-month-old boy with malignant ERRT of the spine, who was staged with F-18 FDG PET/CT, and had his tumor burden assessed with PET/CT after chemotherapy, which altered the subsequent chemotherapy regimen.     

Usefulness of F-18 FDG PET/CT in Assessment of Recurrence of Cervical Cancer After Treatment

Objective

Until now, serum tumor markers, physical examination, and conventional imaging modalities, such as CT or MRI, have been used in assessment of recurrence of cervical cancer after treatment. However, CT and MRI provide only anatomical data, which makes analysis of post-treatment change difficult. This study aims to explore the effectiveness of PET/CT, a new scanning device that combines PET and CT, in evaluation of cervical cancer lesions in patients with suspected recurrence.

Methods

We studied 51 patients suspected of recurrence among those who underwent F-18 FDG PET/CT for cervical cancer follow-up at Gachon University Gil Hospital between June 2006 and August 2009. Patients were considered to be at risk for recurrence if they reported symptoms that were clinically suggestive of recurrence, or if physical examination showed abnormalities, serum tumor marker levels rose, or follow-up images revealed changes, such as new lesions or swelling of previous sites. Sensitivity, accuracy, specificity, and positive and negative predictive values of PET/CT were measured.

Results

A total of 37 patients were confirmed with recurrence or metastasis, 13 of whom were diagnosed histologically. Measured across all patients, PET/CT scored 97.3% on sensitivity, 71.4% on specificity, a positive predictive value of 90%, a negative predictive value of 90.9%, and an accuracy of 90.2%. PET/CT yielded only one false negative diagnosis and four false positives.

Conclusion

As F-18 FDG PET/CT has high sensitivity and negative predictive value in diagnosis of recurrent cervical cancers, it is expected that it will be useful for clinical determination of recurrence and prevention of unnecessary additional treatments. The hope is that a future study on a larger scale will contribute further to determination of the efficacy of PET/CT.