Interim FDG-PET/CT in Hodgkin lymphoma: the prognostic role of the ratio between target lesion and liver SUVmax (rPET).

OBJECTIVE: To evaluate the prognostic role of the ratio between target lesion and liver SUVmax (rPET) in patients with Hodgkin lymphoma (HL) undergoing interim FDG-PET/CT and to compare rPET with the 5-point Deauville Score (5p-DS).

METHODS: Sixty-eight patients with HL undergoing interim FDG-PET/CT after first courses of chemotherapy were evaluated. The receiver operating characteristic (ROC) approach was applied to identify the optimal cutpoint of rPET with respect to progression free survival (PFS). The prognostic significance of rPET was compared with 5p-DS (scores 4 and 5 considered as positive). Positive predictive value (PPV) and negative predictive value (NPV) were calculated using the presence of an adverse event as the gold standard.

RESULTS: The ROC analysis for rPET as a predictor of progression showed an optimal rPET cutpoint of 1.14. Both 5p-DS and rPET were strong outcome predictors (p < 0.001). Patients with negative 5p-DS and patients with rPET <1.14 had a similar two-year PFS (86 and 87 %, respectively). Patients with a positive 5p-DS had a 2-year PFS of 27 %, while patients with rPET >1.14 had a 2-year PFS of 15 %. 5p-DS and rPET cutoff of 1.14 showed a PPV of 58 versus 70 %, and a NPV of 85 versus 86 %, respectively.

CONCLUSIONS: rPET could be considered an accurate prognostic factor in patients with HL undergoing interim FDG-PET/CT. Larger prospective studies are needed to confirm these data.