PHILADELPHIA - The use of 18F-FDG-PET in the diagnosis and staging of small cell lung cancer (SCLC) has received scant attention from researchers, at least compared to the scientific scrutiny lavished on non-small cell lung cancer (NSCLC) as a whole. But on Sunday a group of European nuclear medicine physicians and radiologists offered compelling evidence that the modality should be included in the diagnostic armamentarium devoted to SCLC.
"In the U.S., approximately 170,000 cases of lung cancer are diagnosed each year. Of these, about 20% are small-cell lung cancer cases," Dr. Ingo Brink said at the 2004 Society of Nuclear Medicine meeting.
Brink, from the division of nuclear medicine at the University Hospital Freiburg in Freiburg, Germany, presented the results of a study conducted at the university to evaluate the impact of FDG-PET on the primary staging of patients with SCLC.
"It's amazing that, when compared to the amount of research that's been done on FDG-PET and the staging of non-small cell lung cancer, so little work has been done on the use of FDG-PET to stage small-cell lung cancer," he added.
Accurate staging is important in SCLC. Patients with limited-stage disease may benefit from chemoradiation, whereas those with extensive disease conventionally receive chemotherapy.
The conventional primary imaging protocol for SCLC consists of a chest CT, abdominal CT, cranial CT or MRI, a bone scan, and a bone-marrow biopsy. Brink and his fellow researchers set out to find if FDG-PET has the potential for use as a simple and more accurate staging tool for small-cell lung cancer.
The exam included an "eyes-to-thighs" whole-body PET exam in 125 consecutive patients with SCLC, during primary staging.
"We performed our exams using seven minutes per bed position for emission scans and two minutes per bed position for our transmission scans. The exams were started after a 90-minute uptake period," he reported.
In addition, brain scans with both FDG-PET and cranial MR or CT were acquired in 91 patients, Brink said.
"The results of the FDG-PET exams were compared to the conventional staging procedures, and if discrepancies appeared between the conventional imaging tools and the PET exam, selective additional examinations were performed," he said.
According to Brink, PET detected markedly increased uptake of 18F-FDG in the primary tumors of all 125 SCLC patients. Complete agreement between FDG-PET results and other staging procedures was observed by the researchers in 75 patients.
Differences occurred in 50 patients at 66 sites. Overall, in 48 sites the FDG-PET results were proven to be correct, and were incorrect in 10 of the sites.
"Of the 10 false-positive sites for FDG-PET, eight of them were in the brain," Brink reported.
The remaining areas of discrepancy were in bone (22), lymph nodes (19), liver (9), adrenal glands (4), and lung (4). In eight of the sites, the discrepancies could not be clarified, Brink said.
As for management, the group found that in 15 of the 125 patients, FDG-PET caused a stage migration, with 11 patients correctly upstaged to extensive disease, and three patients correctly downstaged when CT-suspected metastases of the adrenal glands were not confirmed.
"Only one out of the 125 patients was incorrectly staged by FDG-PET, which was missing brain metastases," Brink said.
The sensitivity of FDG-PET was significantly superior to CT in the detection of extrathoracic lymph node involvement (100% versus 70% and a specificity of 98% versus 94%, respectively) and distant metastases outside the brain (98% versus 92% and a specificity of 92% versus 80%, respectively), the researchers reported.
However, FDG-PET found brain metastases in less than 50% of the affected patients (a sensitivity of 46% and a specificity of 97% when compared with cranial CT or MRI), they said.
"We found that cranial MRI cannot be replaced by FDG-PET," Brink stated.
Based on the performance of the modality, the researchers believe that FDG-PET improves the accuracy of SCLC staging. They also noted that all findings considered suspicious for tumor involvement on the other staging procedures were also detected by FDG-PET. For Brink, the efficacy of FDG-PET was clear.
"Using FDG-PET in the diagnosis and staging of small-cell lung cancer may reduce the number of tests and invasive procedures and save time in the management of the disease," he said.
By Jonathan S. Batchelor
AuntMinnie.com staff writer
June 21, 2004
Related Reading
PET Medicare reimbursement -- narrow but widening, June 17, 2004
PET shows power in both small and non-small cell lung cancer staging, survival, June 6, 2004
Use of fused PET/CT images may improve radiation targeting for lung cancer, May 25, 2004
Separating inflammation from malignancy on thoracic FDG-PET, April 9, 2004
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