Visual and quantitative assessment of interim ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography in children with Hodgkin lymphoma

Abstract

The use of risk-adaptive therapy in patients with Hodgkin lymphoma (HL) makes it possible to de-escalate treatment protocols, thereby decreasing the incidence of long-term adverse effects. Metabolic remission as detected by interim positron emission tomography/computed tomography (PET/CT) performed after 2 cycles of chemotherapy is a prognostic factor that could guide further treatment. The generally accepted Deauville 5-point scale (DS) used for the visual assessment of interim PET/CT scans may be prone to inaccuracies. One of the suggested ways to address this problem is to use a quantitative evaluation method (qPET). The aim of our study was to determine the level of discrepancy between DS assigned after visual (vDS) and quantitative (qDS) assessment of detected lesions on interim PET/CT images in children with HL. The study was approved by the Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. Interim PET/CT scans of 115 patients with HL (the median age was 14 years) were retrospectively analyzed using the quantitative (qPET) method to determine qDS. Baseline PET/CT scan findings and medical history data were available for all patients. All imaging studies were performed at the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology between June 2016 and March 2023. Our results showed that with the above approach (availability of initial PET/CT scans and access to the patient’s medical history), discordance between vDS and qDS was about 30%. There was no difference in the patients with a DS of 4 and 5. In other cases, in 31 (27%) patients, vDS and qDS differed by one score: 25 patients with a qDS of 2 had a vDS of 3; 6 patients with a qDS of 3 had a vDS of 4. Factors independently associated with event-free survival were vDS (hazard ratio (HR) 2.49 (1.26–4.93), p = 0.009) and the presence of a bulky tumor (HR 3.12 (1.10–9.64), p = 0.048). Our comparative analysis revealed a discrepancy between the findings obtained by the visual and quantitative assessment methods. In our study, there were no cases of vDS underestimation and, as a consequence, no patients underwent treatment de-escalation. In HL patients with good tumor volume reduction on CT but ambiguous results of interim PET/CT evaluation performed using the vDS (especially in case of DS4 or DS3), quantification software should be used.