Relationship between semiquantitative (18)F-fluorodeoxyglucose positron emission tomography metrics and necrosis in classical Hodgkin lymphoma

Semiquantitative (18)F-fluoro-2-deoxy-D-glucose positron emission tomography ((18)F-FDG PET) parameters have been proposed as prognostic markers in classical Hodgkin lymphoma (cHL). In non-Hodgkin lymphoma necrosis as assessed by (18)F-FDG PET or computed tomography (CT) (necrosis(visual)) correlates with an adverse prognosis. We investigated whether semiquantitative (18)F-FDG PET metrics correlate with necrosis(visual), determined the incidence of necrosis(visual) and explored the prognostic impact of these factors in cHL. From 87 cHL cases treated with ABVD, (escalated) BEACOPP or CHOP chemotherapy between 2010 and 2017, 71 had both a NEDPAS/EARL accredited (18)F-FDG PET and a contrast enhanced CT scan. Semiquantitative (18)F-FDG PET parameters were determined using Hermes Hybrid 3D software. Necrosis(visual), defined by photopenic tumor areas on (18)F-FDG PET and attenuation values between 10 and 30 Hounsfield units (HUs) on CT, was assessed blinded to outcome. Univariate Cox regression survival analyses of progression free survival (PFS) were performed. Necrosis(visual) was observed in 18.3% of cHL patients. Bulky disease (tumor mass >10 cm in any direction) (P = 0.002) and TLG (P = 0.041) but no other semiquantitative parameters were significantly associated with necrosis(visual). In exploratory univariate survival analysis for PFS the covariates IPS, bulky disease, MTV and TLG were prognostic, while necrosis(visual) was not.