Lung Dose and Pneumonitis Risk Following Five-Fraction Breast Radiotherapy

Area of Science:

• Radiation oncology
• Medical physics

Background:

• Five-fraction breast radiotherapy is a common treatment for early-stage breast cancer.
• Symptomatic pneumonitis is a potential side effect of radiation therapy to the chest.
• Understanding lung dose-volume relationships is crucial for minimizing treatment toxicity.

Purpose of the Study:

• To assess the association between lung radiation dose and symptomatic pneumonitis after five-fraction breast radiotherapy.
• To identify strategies for reducing lung radiation exposure and associated risks.

Main Methods:

• Retrospective analysis of 224 early-stage breast cancer patients treated with five-fraction radiotherapy (WBRT or APBI).
• Evaluation of lung dose-volume parameters and their correlation with symptomatic pneumonitis (grade ≥2).
• Analysis of potential dose thresholds for increased pneumonitis risk.

Main Results:

• Symptomatic pneumonitis occurred in 3.6% of patients, mostly mild and self-limiting.
• Increased lung V8Gy, V10Gy, and V20Gy were significantly associated with higher pneumonitis risk (p<0.05).
• A V20Gy threshold of 7.5% identified patients at higher risk (9.0% vs 0.7%).
• Prone positioning for WBRT and APBI were associated with reduced lung V20Gy.

Conclusions:

• Symptomatic pneumonitis risk increases progressively with higher fractional lung doses in five-fraction breast radiotherapy.
• Accelerated partial-breast irradiation or prone positioning may mitigate lung dose and reduce pneumonitis risk in select patients.