Semiquantitative analysis of interim ¹⁸F-FDG PET is superior in predicting outcome in Hodgkin lymphoma patients compared to visual analysis

To investigate the prognostic value of interim PET (PETi) in adult HL patients, comparing visual with semiquantitative analysis.

Retrospective analysis of Hodgkin's lymphoma (HL) patients diagnosed between 2012 and 2016 in the Onco-hematology Department of Instituto Português de Oncologia - Porto (median follow-up: 46.5 months [2.6-66.4]). Fifty-eight patients with available PET at diagnosis (PET0) and PETi data were included. PETi scans were analyzed according to Deauville 5-point scale (5-PS), and cut-off values for changes in maximum standardized uptake value [SUVmax], peak SUV [SUVpeak], metabolic tumour volume [MTV] and total lesion glycolysis index [TLG] between PETi and PET0 were computed using ROC analysis. Visual and semiquantitative data were compared with each other in the prediction of patient outcomes.

Semiquantitative analysis obtained a higher sensitivity for persistent/relapsed disease compared to the 5-PS (70% vs. 10%, respectively), but lower specificity. It also demonstrated better predictive performance for response to first-line therapy (negative predictive value >92%). The positive predictive value was similar for all five measurements. At 60 months of follow-up, there was a significant difference between the progression free survival (PFS) curves of patients with positive and negative PETi according to ΔSUVmax (56.9% vs. 88.0%, p<0.05), ΔSUVpeak (55.9% vs. 88.1%, p<0.05), ΔMTV (35.3% vs. 88.7%, p<0.05), and ΔTLG (42.4% vs. 88.1%, p<0.05). Statistical significance was not reached when considering 5-PS results.

PETi interpretation according to a semiquantitative approach appears to discriminate HL patients better than the visual 5-PS analysis. This could allow better detection of persistent or early relapsed disease, while a negative PETi result could support de-escalating therapy intensity.