Can we obtain prognostic information from healthy tissue uptake and volume in baseline F-FDG PET/CT imaging in diffuse large B-cell lymphoma?

[PURPOSE] Diffuse large B-cell lymphoma (DLBCL) patients often experience relapse or progression after treatment, emphasizing the need for better prognostic markers. This study investigated baseline FDG uptake and volume of healthy tissues and tumours, to assess their association with time-to-progression (TTP) in DLBCL.

[METHODS] This study included 259 newly diagnosed DLBCL patients. Outcome was two-year TTP after treatment initiation. Automatic segmentation of tissues was performed on the low dose CT scans. Tumour lesions were outlined with a semi-automated segmentation method (standardised uptake value ≥ 4) and subtracted from the tissues. Mean standardised uptake value (SUVmean), tissue-to-blood SUVmean ratio, volume, and total lesion glycolysis (TLG) were determined for the spleen, liver, kidneys, lungs, and brain. Only SUVmean and SUVmean ratio were assessed for fat, bone, and skeletal muscle. Intercorrelations among all tissues and correlations with tumour TLG were calculated. Volume and uptake measures were compared between patients with and without progression using the Wilcoxon signed-rank test. Any measure significantly associated with two-year TTP was added to an existing logistic regression model based on baseline tumour characteristics to assess its added prognostic value.

[RESULTS] Patients with progression showed a significantly higher spleen-to-blood SUVmean ratio, lower SUVmean and TLG in the brain, lower SUVmean in skeletal muscle, and a larger liver volume. Liver volume and spleen-to-blood SUVmean ratio did not significantly improve the prediction of two-year TTP compared to the original model only based on tumour characteristics.

[CONCLUSION] Healthy tissue PET/CT measures were significantly associated with two-year TTP in DLBCL patients. However, these measures did not improve the prediction of two-year TTP compared to models using only tumour characteristics.

[TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION] HOVON-84: EudraCT: 2006-005, 174 - 42, retrospectively registered 01-08-2008.