Response assessment by positron emission tomography-computed tomography as compared with contrast-enhanced computed tomography in childhood Hodgkin lymphoma can reduce the need for radiotherapy in low- and middle-income countries

Abstract

Introduction: The InPOG-HL-15-01, a multicentric prospective study, used a risk-stratified and response-based approach with doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) backbone to treat children and adolescents with newly diagnosed Hodgkin lymphoma (HL) and reduce the use of radiation therapy (RT). Children/adolescents with bulky disease or inadequate response at early response assessment (ERA) after two cycles of chemotherapy were assigned to receive RT. For ERA, positron emission tomography computed tomography (PET-CT) was recommended but not mandatory in view of limited access. This study aimed to compare the impact of using contrast-enhanced computed tomography (CECT) and PET-CT on treatment decisions and outcomes.

Methodology: 396 patients were enrolled and 382 had an ERA at the assigned time point. Satisfactory response was defined as Deauville score 3 or less for patients undergoing PET-CT and complete response (CR)/very good partial response (VGPR) for patients undergoing CECT. Outcomes of interest incorporate 5 year event-free survival (EFS), EFS including abandonment (EFSa), and overall survival (OS).

Results: At ERA, satisfactory response was documented in 277 out of 382 (72.5%) participants and this was significantly higher in PET-CT (151 out of 186, 81.2%) as compared with CECT-based assessments (126 out of 196, 64.3%) respectively (p value < .001). Amongst the 203 patients with nonbulky disease (wherein the indication for RT was entirely dependent on ERA), 96 out of 114 (84.2%) and 61 out of 89 (68.5%) patients achieved a satisfactory response according to the PET-CT and CECT (p value = .008) respectively and hence a lesser proportion of patients in the PET-CT arm received RT. Despite a lower usage of RT the 5 year OS of both groups, ERA based on CECT (91.8%) versus PET-CT (94.1%) was comparable (p value = .391) and so was the 5 year EFS (86.7 vs. 85.5%, p value = .724).

Conclusion: Use of PET-CT as the modality for ERA is more likely to indicate a satisfactory response as compared with CECT and thereby decreases the need for RT in response-based treatment algorithm for HL-afflicted children. The reduction in the application of RT did not impact the overall outcome and plausibly would lower the risk of delayed toxic effects.

Keywords: CECT; Hodgkin lymphoma; PET-CT; childhood; radiotherapy.