Radiation induced pneumonitis following whole breast radiotherapy treatment in early breast cancer patients treated with breast conserving surgery: a single institution study

Abstract

Background: Hypofractionated Radiotherapy (RT) regimens for breast cancer, although reduce cost and time for patients and health care systems, could have a negative impact on normal underlying lung tissue. We studied and compared lung function and the post-RT radiological changes using High-Resolution Computed Tomography (HRCT) in early breast cancer patients, treated with 3-Dimentional conformal whole breast radiotherapy (WBRT) using either conventional or hypofractionated regime.

Patients and methods: Between 2008 and 2009, 61 early breast cancer patients (T1-2N0M0) were randomised into two groups .Group A (n=31) received standard radiotherapy with 50Gy/25f/5w plus boost 10Gy/5f/1w to tumour bed. Group B (n=30) received 43.2Gy/16f/22d plus boost 10Gy/5f/1w to tumour bed. Patients of both groups were subjected to dynamic lung testing, using spirometry and gas diffusion tests on Day 0 (D0, before RT), during RT and after completion of RT at 3 and 6 months. HRCT scans were performed in all patients at baseline, and 3,6,12 months after completion of RT. Respiratory symptoms were recorded at 3 and 6 months post completion of RT. Dosimetric factors, such as Central Lung Dose (CLD), lung Volume receiving more 20 Gy (V20), D25 and Mean Lung Dose (MLD) were calculated for all patients.

Results: At 3 months after RT, the pulmonary changes were classified at HRCT as follows: 91.8 % were Grade 0, 8.19 % Grade 1, and 0 % Grade 2. At 6 months, 86.98 % were Grade 0, 11.47 % Grade 1, and 1.6 % Grade 2. At 12 months, 88.52 % were Grade 0, 9.19 % Grade 1 and 3.27% Grade 2. Univariate analysis showed strong association between radiation pneumonitis, age and all dosimetric parameters. There was no association between fractionation type and incidence of RN. FEV1, FVC, FEV 25, FEV 50 and DLCO showed no statistically significant reduction in both treatment groups in 3 and 6 months following completion of RT, compared to baseline. Multivariate analysis showed no relation between HRCT findings and other variables (age, smoking, chemotherapy, hormonotherapy, V20).

Conclusion: Lung toxicity, as assessed with HRCT and PFTs, was minimal in both treatment arms and our results are in consistency with other published data. Hypofractionated RT was a safe modality and well tolerated by the majority of the patients. Longer follow-up is required for robust assessment of incidence of late lung fibrosis in our series.

Keywords: Hypofractionated breast radiotherapy; high resolution computed tomography; radiation pneumonitis; spirometric tests; whole breast radiotherapy.