Fluorodeoxyglucose (FDG) positron emission tomography (PET) in testicular germ cell tumours in adults: preliminary French clinical evaluation, development of the technique and its clinical applications.

Objectives: Metabolic positron emission tomography (PET) is a new imaging m odality for the detection of tumours, which uses fluorodeoxyglucose (FDG) t o demonstrate increased carbohydrate metabolism of malignant cells. The management of testicular germ cell tumours in adults raises three clini cal problems poorly resolved by conventional imaging techniques: - identification of suspected recurrences in a context of elevated circulat ing serum markers, - initial staging assessment after orchidectomy, - evaluation of the response to treatment. Materials and Methods: The authors report the data obtained in 16 patients (6 cases of seminoma and 10 cases of non seminomatous germ cell tumour [NSG CT]), investigated in the Frederic-Joliot Department using a dedicated PET camera, 60 minutes after intravenous injection of 270 MBq of FDG. Results: In 9 cases of assessment of elevated serum markers with no tumour identified by conventional examinations, PET demonstrated images likely to correspond to tumour sites in 7 patients (5 true-positives [TP] and 2 false -positives [FP] due to postoperative inflammatory changes). PET was negativ e in 2 out of 9 patients, in whom subsequent follow-up showed spontaneous b ut delayed return to normal of tumour markers. In 3 of the 4 cases of initial staging of the disease, PET excluded an exte nsion suspected by conventional imaging and the 4th case was a FP for PET. In 3 cases of evaluation of the response to treatment, PET concluded on the absence of viable residual tumour mass, with a false-negative result in on e case. Conclusion: These results are in line with those reported in the literature , which emphasize the diagnostic difficulties encountered in this disease. The significant contribution of FDG-PET should be confirmed by larger serie s of patients investigated by this new modality.