Analysis of predictive factors for lung injury after forward-planned intensity-modulated radiotherapy in whole breast irradiation

Purpose: This study was performed to assess frequency, timings of occurrence, and predictors of radiologic lung damage (RLD) after forward-planned intensity-modulated radiotherapy (FIMRT) for whole breast irradiation. Methods: We retrospectively reviewed medical records of 157 breast cancer patients and each of their serial chest computed tomography (CT) taken 4, 10, 16, and 22 months after completion of breast radiotherapy (RT). FIMRT was administered to whole breast only (n= 152), or whole breast and supraclavicular regions (n =5). Dosimetric parameters, such as mean lung dose and lung volume receiving more than 10 to 50 Gy (V₁₀-V₅₀), and clinical parameters were analyzed in relation to radiologic lung damage. Results: In total, 104 patients (66.2%) developed RLD after whole breast FIMRT. Among the cases of RLD, 84.7% were detected at 4 months, and 15.3% at 10 months after completion of RT. More patients of 47 or younger were found to have RLD at 10 months after RT than patients older than the age (11.7% vs. 2.9%, p= 0.01). In univariate and multivariate analyses, age > 47 and V₄₀ > 7.2% were significant predictors for higher risk of RLD. Conclusion: RLD were not infrequently detected in follow-up CT after whole breast FIMRT. More detected cases of RLD among younger patients are believed to have developed at later points after RT than those of older patients. Age and V₄₀ were significant predictors for RLD after whole breast intensity-modulated radiotherapy.