Estimation of overall pulmonary function after irradiation using dose-effect relations for local functional injury

Area of Science:

• Medical Physics
• Radiation Oncology
• Pulmonary Medicine

Background:

• Malignant lymphoma treatment often involves radiation therapy, which can cause pulmonary complications.
• Predicting pulmonary function post-irradiation is crucial for patient management and treatment planning.

Purpose of the Study:

• To develop a method for predicting pulmonary function changes 3-4 months after irradiation for malignant lymphoma.
• To correlate three-dimensional (3-D) dose distribution with post-irradiation pulmonary function outcomes.

Main Methods:

• Calculated dose-effect relations for local perfusion (Q) and ventilation (V) reduction in 25 patients using SPECT and CT data.
• Combined individual 3-D dose distributions with average dose-effect relations to estimate overall lung response parameters.
• Correlated these parameters with changes in standard lung function tests and radiation pneumonitis incidence.

Main Results:

• The overall response parameter for perfusion showed significant correlations with changes in Vital Capacity (r=0.53) and Forced Expiratory Volume at 1s (r=0.71).
• Similar correlations were observed for the ventilation response parameter.
• While not statistically significant, patients who developed radiation pneumonitis had a higher average perfusion response parameter (13.2%) compared to those who did not (10.5%).
• A dose-dependent increase in radiation pneumonitis incidence was observed with higher perfusion response parameters.

Conclusions:

• An overall response parameter, calculated from 3-D dose distribution and average dose-effect relations, can predict radiation-induced pulmonary function changes.
• This parameter may also offer predictive value for radiation pneumonitis incidence in patients with malignant lymphoma undergoing irradiation.