Fluorocholine PET/CT aids prostate cancer staging and management

The power of F-18 fluorocholine (FCH) as a guide for the clinical management of prostate cancer is gaining recognition. Dynamic whole-body PET/CT performed with F-18 FCH accurately assesses the extent of lymphatic involvement from prostate cancer, according to findings from two years of experience at the PET/CT center of Hospital of the Holy Sister in Linz, Austria.

A study involving preoperative staging for 49 patients and postoperative follow-up for 61 patients found that the probe is equally adept at identifying bone metastases associated with prostate cancer. Results were presented in March by Dr. Warner Langsteger, director of nuclear medicine and endocrinology at Holy Sister, at the 2005 Academy of Molecular Imaging meeting in Orlando, Florida.

For staging, positive FCH PET/CT findings were generated for 16 of 18 cases confirmed with biopsy: 4% of the cases were downstaged mainly because of suspicious bone lesions that were negative for uptake on the FCH PET/CT scans, and 12% of the presurgical cases were upstaged.

FCH PET/CT uncovered new bone metastases in four cases, and in two cases, it helped identify positive lymph node involvement. As a result, radiation therapy was prescribed for these patients, and surgery was canceled, Langsteger said.

FCH PET/CT agreed with the laboratory finding for all 31 patients whose preoperative conditions were confirmed with postoperative histology, according to Langsteger. The procedures identified positive lymph nodes larger than 5 mm in four patients. Among these patients, two positive lymph nodes, diagnosed with histology, were not found with FCH PET/CT. Histology revealed that these metastases ranged in size from 5 to 8 mm.

F-18 FCH has enjoyed positive reviews elsewhere in Europe during its five-year history. Timothy R. DeGrado, Ph.D, now at Indiana University in the U.S., first synthesized the probe at Duke University in 2000. During a plenary session at the ECR in March, Prof. Gustav K. von Schulthess, director of nuclear medicine at University Hospital in Zurich, Switzerland, predicted that F-18 FCH would be the next positron-emitting radiopharmaceutical agent to join F-18 FDG in routine clinical use.

Langsteger was also encouraged about the probe's potential. The results of his study led him to conclude that dynamic PET/CT with F-18 FCH will become a valuable noninvasive diagnostic tool for prostate cancer, especially for differential diagnoses involving lymph nodes and the ureter.

PET/CT may boost physician confidence, but the fusion imaging technique is basically equivalent to PET alone for staging or restaging lymphoma.

Dr. Carina Mari Aparici, chief resident of nuclear medicine at Stanford University in California, came to this conclusion after evaluating the staging and restaging of Hodgkin's and non-Hodgkin's lymphoma for vatious cross-sectional modalities. She presented results from her study of 167 patients at the Academy of Molecular Imaging meeting.

Aparici found that PET/CT had a slight though statistically insignificant edge over PET alone. Radiologists interpreting the results correctly staged 92% of the cases based on PET/CT. For PET alone, accuracy was 90%.

The radionuclide procedures outperformed the protocols involving CT alone by a wide margin. Radiologists who read noncontrast CT scans were able to attain only a 42% accuracy rate. Only 27% of the cases were correctly staged when the radiologists based their findings on contrast-enhanced CT scans.

Overall, staging and restaging contributed to patient management changes in 117 cases. The PET/CT studies correctly led the reader to 99% of those recommendations. PET alone would have correctly pointed to 98% of the revised plans. Nonenhanced and contrast-enhanced CT would have led to correct calls in 45% and 2% of the cases, respectively.

The few differences between PET/CT and PET findings stemmed from PET's inability to identify retrocrural and costophrenic lymph nodes that changed the stage of a patient, Aparici said. PET/CT was more capable than PET alone at differentiating between brown fat and active lesions in two cases.

"Better staging leads to better treatment," Aparici said.

Although the performance of PET/CT and PET was nearly identical, Aparici gave PET/CT an edge over PET alone because it offers the reader anatomic information that cannot be seen on PET images.

"We think it is going to improve the management of these patients," she said.