The following is a summary of “Dose-volume predictors of radiation pneumonitis following thoracic hypofractionated radiotherapy,” published in the November 2023 issue of Pulmonology by Sasse et al. 

Hypofractionated radiation therapy (HFRT) is a frequently used treatment for thoracic tumors, typically administered at 60 Gy in 15 fractions. This study aimed to identify dosimetric factors associated with radiation pneumonitis in patients receiving HFRT at 4 Gy per fraction, specifically examining lung V20, mean lung dose (MLD), and lung V5 as potential predictors of grade ≥2 pneumonitis.

All patients received thoracic HFRT, either 60 Gy in 15 or 72 Gy in 18 fractions, at a single healthcare system between 2013 and 2020. Tumors near critical structures (trachea, proximal tracheobronchial tree, esophagus, spinal cord, or heart) within 2 cm were classified as central, while those closer were deemed ultra-central (within 1 cm). The primary endpoint was grade ≥2 pneumonitis. Logistic regression analyses, adjusted for target size and dosimetric variables, were utilized to determine a dose threshold associated with <20% risk of grade ≥2 pneumonitis.

Over a median 24.3-month follow-up, 18 patients (16.8%) developed grade ≥2 radiation pneumonitis, with no significant difference between the two dose regimens (17.3% vs. 16.3%, p=0.88). Four patients (3.7%) experienced grade ≥3 pneumonitis, including two grade 5 cases. Patients with grade ≥2 pneumonitis exhibited significantly higher lung V20 (mean 23.4% vs. 14.5%, p<0.001), MLD (mean 13.0 Gy vs. 9.5 Gy, p<0.001), and lung V5 (mean 49.6% vs. 40.6%, p=0.01). Dose thresholds for a 20% risk of grade ≥2 pneumonitis were lung V20 <17.7%, MLD <10.6 Gy, and V5 <41.3%. Multivariable analysis revealed a significant association between lung V20 and grade ≥2 pneumonitis (adjusted OR 1.48, p=0.03).

To minimize the risk of grade ≥2 radiation pneumonitis when administering 4 Gy per fraction at either 60 Gy or 72 Gy, it is recommended to maintain lung V20<17.7%. MLD<10.6 Gy and V5<41.3% can also be considered as lower-priority constraints. However, further validation is necessary before incorporating these constraints into clinical practice or trial planning guidelines.

Source: sciencedirect.com/science/article/abs/pii/S1879850023003041