Barrington, S F, Kirkwood, A A, Franceschetto, A, Fulham, M J, Roberts, T H, Almquist, H, Brun, E, Hjorthaug, K, Viney, Z N, Pike, L C, Federico, M, Luminari, S, Radford, J, Trotman, J, Fossa, A, Berkahn, L, Molin, D, D'Amore, F, Sinclair, D A, Smith, P, O'Doherty, M, Stevens, L & Johnson, P W 2016, ' PET-CT for staging and early response : results from the Response-Adapted Therapy in Advanced Hodgkin Lymphoma study ', Blood, vol. 127, no. 12, pp. 1531-1538 . https://doi.org/10.1182/blood-2015-11-679407
International guidelines recommend that positron emission tomography-computed tomography (PET-CT) should replace CT in Hodgkin lymphoma (HL). The aims of this study were to compare PET-CT with CT for staging and measure agreement between expert and local readers, using a 5-point scale (Deauville criteria), to adapt treatment in a clinical trial: Response-Adapted Therapy in Advanced Hodgkin Lymphoma (RATHL). Patients were staged using clinical assessment, CT, and bone marrow biopsy (RATHL stage). PET-CT was performed at baseline (PET0) and after 2 chemotherapy cycles (PET2) in a response-adapted design. PET-CT was reported centrally by experts at 5 national core laboratories. Local readers optionally scored PET2 scans. The RATHL and PET-CT stages were compared. Agreement among experts and between expert and local readers was measured. RATHL and PET0 stage were concordant in 938 (80%) patients. PET-CT upstaged 159 (14%) and downstaged 74 (6%) patients. Upstaging by extranodal disease in bone marrow (92), lung (11), or multiple sites (12) on PET-CT accounted for most discrepancies. Follow-up of discrepant findings confirmed the PET characterization of lesions in the vast majority. Five patients were upstaged by marrow biopsy and 7 by contrast-enhanced CT in the bowel and/or liver or spleen. PET2 agreement among experts (140 scans) with a κ (95% confidence interval) of 0.84 (0.76-0.91) was very good and between experts and local readers (300 scans) at 0.77 (0.68-0.86) was good. These results confirm PET-CT as the modern standard for staging HL and that response assessment using Deauville criteria is robust, enabling translation of RATHL results into clinical practice.