Radiation Pneumonitis in Pediatric Hodgkin Lymphoma Patients receiving Radiotherapy to the Chest

Abstract

Although there is adequate information on the incidence and risk factors for radiation pneumonitis in adults, it is limited in children. One may speculate that children may have better tolerance than adults as they do not have the same risk factors for lung injury such as smoking and asbestos exposure; furthermore, radiotherapy (RT) doses delivered to the chest in pediatric malignancies are lower compared to patients treated for lung cancer. The purpose of this study is to determine the incidence of radiation pneumonitis (RP) in the pediatric population receiving RT for Hodgkin lymphoma (HL). A retrospective chart review was conducted of pediatric HL patients who received involved site thoracic RT after induction chemotherapy. The National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) version 4.03 was used to determine the RP grade (Grade 1: asymptomatic, clinical or diagnostic observations only, intervention not indicated, Grade 2: symptomatic, medical intervention needed, Grade 3: severe symptoms, oxygen indicated, Grade 4: life threatening respiratory compromise including tracheotomy and intubation, Grade 5: death). Parameters analyzed included gender, age, bleomycin dose, and RT dosimetric variables such as mean total lung dose, mean individual (right versus left) lung dose, and V5 to V25. From 2008-2016, 54 patients with HL received RT to the chest and had follow-up and dosimetry information. There were 29 females; median age was 15 years (3-18 years). All patients received induction chemotherapy with a regimen that included bleomycin (median dose 60 IU/m2). The most common regimen was ABVE-PC based chemotherapy (n = 48). All received a prescribed dose of 21 Gy in 14 fractions to part of the chest. Median follow-up from completion of radiotherapy was 39.5 months. Three patients (5.6%) developed RP; two had Grade 1 while one had Grade 2 RP. RP was seen only in patients with individual mean lung dose (MLD) > 13.8 Gy. The incidence of RP according to MLD was 0 of 91 lungs with MLD < 13.7 Gy vs. 3 of 17 (17.6%) with MLD > 13.8 Gy (p < 0.005). RP was seen in 0 of 92 lungs with V20 < 35%, 1 of 7 (14.2%) receiving V20 from 35 to 42%, and 2 of 9 (22.2%) with V20 > 43% (p < 0.005). RP was also more common in lungs with V5 > 75% (p =0.02), V10 > 64% (p = 0.02) and V15 > 47% (< 0.005). We did not find any association between age, gender, bleomycin dose and development of RP. RP in pediatric HL patients is an uncommon complication. MLD, V20, V15, V10 and V5 correlated with RP. Further development of pediatric-specific models for RP is necessary as radiation treatment techniques improve.