Predicting the Risk of Radiation Pneumonitis and Pulmonary Function Changes after Breast Cancer Radiotherapy

Radiotherapy plays an important role in the treatment of breast cancer. In the process of radiotherapy, the underling lung tissue receives higher doses from treatment field, which led to incidence of radiation pneumonitis.

The present study aims to evaluate the predictive factors of radiation pneumonitis and related changes in pulmonary function after 3D-conformal radiotherapy of breast cancer.

In prospective basis study, thirty-two patients with breast cancer who received radiotherapy after surgery, were followed up to 6 months. Respiratory symptoms, lung radiologic changes and pulmonary function were evaluated. Radiation pneumonitis (RP) was graded according to common terminology criteria for adverse events (CTCAE) version 3.0. Dose-volume parameters, which included percentage of lung volume receiving dose of d Gy (V₅-V₅₀) and mean lung dose (MLD), were evaluated for RP prediction. Pulmonary function evaluated by spirometry test and changes of FEV1 and FVC parameters.

Eight patients developed RP. Among the dose-volume parameters, V₁₀ was associated to RP incidence. When V₁₀<40% and V₁₀≥40% the incidences of RP were 5.26% and 61.54%, respectively. The FEV1 and FVC had a reduction 3 and 6 months after radiotherapy, while only FEV1 showed significant reduction. The FEV1 had more reduction in the patients who developed RP than patients without RP (15.25±3.81 vs. 9.2±0.93).

Pulmonary function parameters, especially FEV1, significantly decreased at 3 and 6 months after radiotherapy. Since most patients with breast cancer who developed RP did not show obvious clinical symptoms, so spirometry test is beneficial to identify patients with risk of radiation pneumonitis.