Abstract P075

Response Adapted Therapy of Pediatric Classic Hodgkin Lymphoma According to Modified EURO-NET Protocol-Single Center Experience

Background: Hodgkin lymphoma (HL) represents about 5–7% of all malignancies in children, with a 5-year probability of overall survival (pOS) exceeding 90%. Radiotherapy containing regimen bear an increasing risk for late effects particularly secondary malignancies and cardiovascular disease. The omission of radiotherapy in patients with an adequate 18FDG-PET CT metabolic response after two intensive induction chemotherapy cycles has become the current treatment approach in the EuroNet-PHL consortium.

Aim: To report the results of HL patients treated according to the EuroNet protocol at the Children Cancer Hospital Egypt (CCHE 57357).

Methodology: This retrospective study included all patients diagnosed with classic HL, and treated as per EuroNet protocol during the period from 2/2019 till end of 12/2023. Patients demographic data (age, sex), disease characteristics; histologic subtypes, initial ESR, stage, B symptoms, treatment groups (TG), response to induction chemotherapy either adequate or inadequate according to interim 18FDG-PET CT, radiotherapy dose and duration, outcomes including overall (OS), event free (EFS) survival were collected and analyzed.

Results: Seven hundred and nineteen patients were included in the study. The most common age group was from 5-15 years (68.8%). There was a clear male predominance (69.1%). Nodular sclerosis was the most common pathologic subtype (60.3%). Stage II-A was the most commonly seen (24.3%). TG 3 according to EuroNet risk stratification was predominant (40.0%). Seventy percent of the patients had an adequate metabolic and radiologic response, while 26.2% received upfront radiotherapy. Relapse rate was 13.4% and progression on chemotherapy was seen in 0.28%.

The 5-year OS was 96.1 % (95 % CI: 93.7% - 98.5%), while the EFS was 82.7 % (95 % CI: 78.4% - 85.8%). For patients with adequate response, the 5- year EFS was 86.9 % (95 % CI: 83.2% - 90.6%), compared to 73.2 % (95 % CI: 64.2% - 82.2%) for those with inadequate response.

Conclusion: EuroNet risk adapted response adapted protocol for pediatric classic HL seems a good strategy. The rationale is to reserve radiotherapy, with its potential serious late effects to patients with high risk disease. In addition to interim 18FDG-PET CT results, serum disease response biomarkers (CD163, TARK, ctDNA) may be able in the future to refine risk stratification, with the potential of adding targeted and/or immunotherapy as upfront treatment for high risk patients.