Objective Melanoma has a strong tendency for metastasis within the brain. There are no validated recommendations for the surveillance of the brain in patients undergoing treatment for advanced melanoma. We investigated the value of including the brain in the field of view (FOV) of total body FDG-PET/CT scans in patients with advanced melanoma who clinically were not suspected to have brain involvement.
Materials and method Melanoma patients who were examined between 01-04-2008 and 30-11-2009, by total body FDG-PET/CT (including the entire brain in the FOV) and subsequent MRI within three months of the FDG-PET/CT were identified in our institutional data base. The CT portion of the FDG-PET/CT-scan was acquired in the venous phase after IV-contrast administration. MRI of the brain included gadolinium enhanced T1, T2 and FLAIR sequences.
Results A total of 49 examinations were identified in 34 patients [17 M, 17 F; mean age, 52.7 y (range 26–80 y)]. The average time interval between FDG-PET/CT and MRI was 15.8 days. Seventy-three lesions suggesting the presence of brain metastases were identified by FDG-PET/CT (36 were only identified on CT, 34 were identified on both FDG-PET and CT; 26 were hypometabolic and 8 hypermetabolic; 3 lesions were identified only on FDG-PET/CT as focal hypermetabolic areas). One hundred thirty-three lesions were identified by subsequent MRI. When compared to MRI, FDG-PET/CT had a sensitivity of 55% for detecting individual lesions; no true negative lesions were present. When considering the results per examination, 22/49 FDG-PET/CT examinations were considered positive for the presence of CNS involvement and all of these cases were confirmed by MRI. MRI demonstrated brain metastases in 23 patients. In 18 patients suspicious lesions were identified both on FDG-PET/CT, as well as on contrast enhanced CT, whereas in 4 cases lesions were only detected on CT. The sensitivity, specificity, and accuracy of FDG-PET/CT scans compared to the MRI was 96%, 100%, and 98% respectively.
Conclusion Including the brain in the FOV for follow-up of advanced melanoma with FDG-PET/CT is useful to detect brain metastases at an early stage. This could potentially lead to more efficient treatment and prevention of CNS metastasis related morbidity. We therefore recommend the inclusion of the brain in the FOV in patients undergoing FDG-PET/CT during follow-up for advanced melanoma. MRI remains the method of choice for further evaluation of the brain when metastases are identified on FDG-PET/CT or in case of a negative FDG-PET/CT with suspicious clinical findings.