Positron emission tomography with F-18-FDG to detect residual disease after therapy for malignant lymphoma

We retrospectively evaluated the use of F-18-FDG PET for assessment of resi dual disease in 27 patients after therapy for malignant lymphoma. The image s were evaluated qualitatively and quantitatively using standardized uptake values (SUV). All findings were validated either by biopsy or by clinical follow-up and compared with corresponding CT findings. The impact of blood glucose concentration, body weight, body surface area, lesion diameter and the time between injection and imaging on the SUVs were analysed. All 15 pa tients with biopsy-proven residual disease or relapse during follow-up and 11 of 12 patients who remained relapse-free were correctly identified by qu alitative interpretation of the PET images. A case of pneumonitis after rad iotherapy/chemotherapy accounted for the only false-positive finding. Compa red with CT imaging, PET had a significantly higher specificity (P < 0.01), accuracy (P < 0.05) and positive predictive value (P < 0.05). The mean and maximum SUV of the tumour lesions were positively correlated to lesion dia meter (P < 0.01) and imaging time post-injection (P < 0.01). Standardized u ptake values corrected for the partial volume effect and normalized to a st andardized imaging time (SUVBPT) were significantly higher (P < 0.05) in hi gh-grade than in low-grade non-Hodgkin's lymphoma. In conclusion F-18-FDG P ET may help in the identification of patients who need additional treatment after the completion of conventional therapy. Qualitative image interpreta tion appears sufficient for this purpose. ((C) 1998 Lippincott Williams & W ilkins).