Abstract
Introduction: This study evaluates the changes in the lung volume (LV) exposed radiation during the breath cycle and whether these volume differences have an effect on both lung and target doses in breast carcinoma patients. Material and Methods: Ten patients with left breast carcinoma underwent breast conservative surgery or mastectomy receiving radiotherapy (RT) (breast or chest wall and regional lymph nodes) were included. For this study, planning computerized tomography (CT) images were obtained during deep inspiration (DI) and end of expiration (EE), besides free breathing (FB) to simulate breath cycles. Three-dimensional conformal or intensity-modulated RT planning was done to obtain dose-volume information using CT series taken FB, DI and EE. The treatment plan was done with FB images and exported to the DI and EE scans and re-calculated. Volume changes and calculated dose differences according to breath cycles were compared. Results: There were significant differences in the whole LV, ipsilateral LV and contralateral LV between FB-DI and EE-DI while no significant difference was seen between FB and EE. V20 was lower during DI than FB and EE but the difference was not significant. There was no significant variation in whole breast dose although significant dose variations were observed in mean MI, supraclaviculary and level III axillary lymph node doses between breath cycles. Conclusion: Breath cycle had no significant effect on whole breast dose although significantly changed regional lymph node doses in patients with breast carcinoma receiving whole breast and regional lymph nodes radio-therapy. V20 dose was lower during DI than FB and EE, but the difference was not significant.
Highlights
This study evaluates the changes in the lung volume (LV) exposed radiation during the breath cycle and whether these volume differences have an effect on both lung and target doses in breast carcinoma patients
The differences between free breathing (FB)-deep inspiration (DI) were found significant for criteria namely absolute whole, ipsilateral and contralateral lung volumes, whole lung V5, ipsilateral lung V5, whole lung volume receiving 20 Gy (V20), lung volume receiving prescription dose (PD), ipsilateral lung volume receiving PD, % lung volume receiving PD and % ipsilateral lung volume receiving PD
There was a significant differences between mean MI and level III axillary lymph node doses belongs to FB and DI and mean level II axillary doses belongs to FB and end of expiration (EE) (Figure 3)
Summary
This study evaluates the changes in the lung volume (LV) exposed radiation during the breath cycle and whether these volume differences have an effect on both lung and target doses in breast carcinoma patients. Conclusion: Breath cycle had no significant effect on whole breast dose significantly changed regional lymph node doses in patients with breast carcinoma receiving whole breast and regional lymph nodes radiotherapy. Radiation induced lung side effects can occur during and after completion of radiotherapy [3] These side effects can manifest with different clinical symptoms such as radiation pneumonitis (shortness of breath) or physical changes such as bronchial stricture; they can be detected using imaging techniques e.g. density changes in computerized tomography (CT) and perfusion-ventilation defects in SPECT scintigraphy [3,4]. In order to reduce the radiation exposed hearth and lung volume, sophisticated radiotherapy techniques such as respiratory-gated radiotherapy have been used [9,10]
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