Incidence and correlates of radiation pneumonitis in pediatric patients with partial lung irradiation

Abstract

Purpose: To provide a radiation pneumonitis risk estimate and investigate the correlation of clinical and dosimetric factors in pediatric patients receiving chest irradiation.

Methods and materials: A total of 122 patients diagnosed with sarcoma or Hodgkin lymphoma who received radiotherapy to the chest were evaluated for symptomatic radiation pneumonitis (Common Toxicity Criteria Grade 1 with respiratory symptom or higher grade). Pneumonitis data were collected from either prospective toxicity screenings as part of a clinical trial or through chart review. Dosimetric parameters including V(10)-V(25), mean lung dose, binned lung dose, and tissue complication probability models were used, as well as clinical features to correlate with the development of pneumonitis.

Results: The 1- and 2-year cumulative incidence of symptomatic radiation pneumonitis for all patients was 8.2% and 9.1%, respectively. Nine patients experienced symptomatic Grade 1 toxicity, and 2 experienced Grade 2. From univariate analysis, chemotherapy containing bleomycin (chi(2) test, p = 0.027) and V(24) (logistic regression, p = 0.019) were the clinical and dosimetric factors that resulted in statistically significant differences in the occurrence of pneumonitis. The probability of pneumonitis increased more dramatically with increasing V(24) in patients receiving bleomycin than in those who did not. Adult tissue complication models did not differentiate pediatric patients with radiation pneumonitis from those without.

Conclusions: The incidence of symptomatic radiation pneumonitis in pediatric patients is low and its severity mild. Parameters frequently used in adult radiation oncology provide some guidance as to risk, but pediatric patients warrant their own specific models for risk assessment, incorporating dosimetry and clinical factors.

Fig. 1

Cumulative incidence of symptomatic radiation pneumonitis in 122 pediatric patients with lung irradiation.

Fig. 2

Dose–volume histogram overlays of the total lung from radiotherapy plans of 99 children with Hodgkin lymphoma (a) and 23 children with sarcoma (b). The bold curves are from the patients with symptomatic radiation pneumonitis. Among them, the dashed curves are from the ones with Grade 2 radiation pneumonitis.

Fig. 3

Scatter plots of selected dose–volume histogram parameters for 122 Hodgkin lymphoma and sarcoma patients. Circles represent patients without symptomatic radiation pneumonitis. Squares represent patients with symptomatic radiation pneumonitis. Open squares represent Grade 1 pneumonitis and solid squares Grade 2. MLD = mean lung dose; NTCP = normal tissue complication probability; risk = radiation pneumonitis risk.

Fig. 4

Predicted probability of symptomatic radiation pneumonitis (Grade ≥1) based on bivariate logistic regression for patients who received chemotherapy containing bleomycin (upper curve) and those who did not (lower curve).