Role of ¹⁸F-FDG PET/CT in primary brain lymphoma

Objective: To study the usefulness of ¹⁸F-FDG PET/CT in the initial evaluation and in the response assessment in primary brain lymphoma.

Material and methods: A retrospective analysis was carried out on 18 patients diagnosed with primary brain lymphoma, a histological subtype of diffuse large B-cell lymphoma, on whom an initial ¹⁸F-FDG PET/CT and MRI was performed, with 7 of the cases being analysed after the completion of treatment in order to assess response and clinical follow up.

Results: Initial ¹⁸F-FDG PET/CT showed 26 hypermetabolic foci, whereas 46 lesions were detected by MRI. The average SUV maximum of the lesions was 17.56 with T/N 3.55. The concordance of both tests for identifying the same number of lesions was moderate, obtaining a kappa index of 0.395 (P<.001). In the evaluation of treatment, MRI identified 16 lesions compared to 7 pathological accumulations observed by ¹⁸F-FDG PET/CT. The concordance of both tests to assess type of response to treatment was moderate (kappa index 0.41) (P=.04). In both the initial evaluation and the assessment of the response to treatment, PET/CT led to a change strategy in 22% of patients who had lesions outside the cerebral parenchyma.

Conclusions: MRI appears to be the method of choice for detecting brain disease in patients with primary brain lymphoma, whereas ¹⁸F-FDG PET/CT seems to play a relevant role in the assessment of extra-cerebral disease.