FDG-PET Offers Superior Melanoma Staging and Follow-up

TORONTO--Patients with high-risk melanoma may benefit from use of whole-body 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) for primary staging, researchers from the University of Frankfurt/Main reported at the 45th Annual Meeting of the Society of Nuclear Medicine.

Improved Diagnostic Accuracy

"We find an improved diagnostic accuracy using FDG-PET to assess patients," said Dr. Andreas Hertel, Department of Nuclear Medicine, University Hospital, Frankfurt. "The sensitivity and specificity of PET is superior, particularly in high-risk patients with metastases."

This prospective study included 100 patients with confirmed high-risk malignant melanoma. They were evaluated using whole-body FDG-PET and conventional diagnostic imaging (MRI of the brain; x-ray of the chest; CT of the thorax, abdomen, and pelvis; ultrasound of the abdomen; high-resolution lymph node sonography; and skeletal scintigraphy).

Fifty-two of the patients were studied at primary diagnosis of their disease and 48 at follow-up with suspicion of recurrence. Every identified lesion was confirmed by histology.

For the patients with a primary diagnosis, PET was 100% sensitive in detecting metastases (see figure), while conventional imaging did not identify any of the nine metastatic lesions. In the patients with suspected recurrence, 121 lesions were detected, 111 (92%) by PET and 69 (57%) by conventional imaging. The conventional methods did not identify all patients with progression and detected significantly fewer metastases.

Results Depended on Site

Results also depended on specific sites (see table): While PET yielded a higher sensitivity in detecting cervical metastases (100% vs 66.6%) and abdominal metastases (100% vs 26.6%), CT proved to be superior in detecting small lung metastases (87% vs 69.6%).

"We demonstrated that we can find very small lesions with a high sensitivity and specificity compared to CT, especially in the primary staging of high-risk patients," Dr. Hertel said. "We believe that PET should replace CT as the front-line procedure in staging patients."

Speaking at a press conference held in conjunction with the meeting, lead author Richard P. Baum, MD, chair of the Bad Berka PET Center, said: "If we detect lesions with FDG-PET and plan to operate, then we need CT and/or MRI for anatomic information and surgical planning, but we don’t need those tests for staging a patient with malignant melanoma as the front-line procedure."

Dr. Baum also pointed out that use of PET can save considerable time. "We can do a whole-body FDG-PET scan in one hour," he said, "compared to multiple days in the hospital for a standard diagnostic workup."