Outcomes of Proton Therapy to Infradiaphragmatic Sites in Pediatric
Patients with Hodgkin Lymphoma
Abstract
Background: Proton therapy (PT) has potential advantages in pediatric
Hodgkin lymphoma (pHL). However, there is limited data on PT,
specifically to infradiaphragmatic targets. We report on PT planning
details, doses achieved to organs at risk (OARs), and clinical and
toxicity outcomes for patients with pHL who received PT to
infradiaphragmatic regions. Methods: This is a retrospective study
including patients treated between 2011-2022. Demographic and clinical
factors were collected, and toxicity was reported using CTCAE version
5.0. Dosimetric and clinical factors associated with key outcomes were
assessed via Cox regression. Photon plans were generated for all
patients, and the paired t-test or Wilcoxon signed rank sum test
were used for dosimetric comparisons. Results: Twenty-one patients
comprising 22 PT courses were included. Median follow-up was 5.0 years
and mean age was 14.2 years. Median dose was 21 Gray equivalent (GyE)
over 14 fractions. Top acute grade 1 (G1) toxicities included fatigue
(59%) and anorexia (36%). Rates of acute G2 and G3+ toxicity were 18%
and 0%, respectively. After PT, no local or marginal failures occurred.
5% experienced disease progression which were all successfully
salvaged, and all patients were alive and disease-free at last
follow-up. No secondary malignancies developed. Compared to photon
radiation, PT achieved significantly lower doses to the bowels, stomach,
spleen, pancreatic tail, liver, and kidneys. Conclusions: PT is
well-tolerated and leads to excellent oncologic and toxicity outcomes
with long-term follow-up. PT confers dosimetric advantages when compared
to photons.