Response Assessment by PET CT as compared to CECT in childhood Hodgkin
Lymphoma can reduce the need for radiotherapy in low and middle income
countries
Abstract
Introduction: The InPOG-HL-15-01, a multi-centric prospective study used
a risk-stratified and response-based approach with a doxorubicin,
bleomycin, vinblastine and dacarbazine (ABVD) backbone to treat children
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 2 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) vs PET-CT
on treatment decisions and outcomes. Methodology: 396 patients were
enrolled and 382 had an ERA at the assigned time point. Results: At ERA,
satisfactory response was documented in 277/382 (72.5%) participants
and this was significantly higher in PET-CT (151/186, 81.2%) as
compared to CECT (126/196, 64.3%) respectively (p
value<0.001). Amongst the 203 patients with non-bulky disease
(wherein the indication for RT was entirely dependent on ERA), 96/114
(84.2%) and 61/89 (68.5%) patients achieved a satisfactory response
according to the PET-CT and CECT (p value=0.008) respectively and hence
a lesser proportion of patients in the PET-CT arm received RT. Despite a
lower usage of RT the 5 year overall survival (OS) of both groups- ERA
based on CECT (91.8%) vs PET-CT (94.1%) was comparable (p value=0.391)
and so was the 5 year event free survival (EFS) (86.7 vs 85.5%, p
value=0.724). Conclusion: Use of PET-CT as the modality for ERA is more
likely to indicate a satisfactory response as compared to 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.