Conventional staging and 18 F-FDG-PET staging of malignant melanoma

Background. Preliminary reports suggest that PET using 18F-FDG may be a valuable diagnostic tool in patients with advanced malignant melanoma. Therefore, the aim of this study was to compare the findings of 18F-FDG-PET and those of conventional imaging including physical examination for both primary and follow- up staging of patients with malignant melanoma. Patients and methods. Thirty-five patients with histologically proven malignant melanoma underwent 61 PET examinations. After an intravenous injection of 370 MBq 18F-FDG, whole-body images were acquired on an ECAT EXACT 47 (921) with an axial field-of-view of 16.2 cm. Moreover, all patients underwent physical examination and conventional imaging, i.e. ultrasound, CT, and MRI within a two-week interval after 18F-FDG-PET. Based on the findings of both staging procedures, the patients were classified according to UICC. Results. In primary staging or follow-up, 5 out of 35 patients were classified as stage I by conventional staging. Seven out of 35 patients were classified as stage II. The remaining 23 patients were initially classified as stage III. In the follow-up, two out of the latter 23 patients were upstaged to stage IV. However, none of these patients was classified as stage IV in primary staging by conventional diagnostic procedures. According to the results of 18F-FDG-PET, 9 out of 35 patients revealed neither evidence for distant metastases nor presence of lymph node metastases in primary staging (stage I/II). However, initially 21 out of 35 patients were suspected for lymph node metastases but no distant metastases (stage III). Moreover, 18FFDG- PET suspected 5 patients, initially classified as stage IV, for distant metastases. However, in the follow- up, 18F-FDG-PET turned out to be false-positive for distant metastases in one out of the latter 5 patients; therefore, this patient was staged down to stage III. As compared to conventional diagnostic work-up, 18F-FDG-PET revealed the corresponding tumor stage in 17 out of 35 patients (49 %). However, 14 patients (40%) were staged up by 18F-FDG-PET and 4 patients (11%) were staged down by 18F-FDG-PET in primary staging or follow-up investigations. With respect to anatomical localization, the majority of false-negative PET lesions were lymph node metastases close to the skin area. Conclusions. Our results underline the added value of 18F-FDG-PET in staging of malignant melanoma. Since further treatment mainly depends on the clinical stage, 18F-FDG-PET might help to select the appropriate treatment protocol for each individual patient.