The Differential Impact of Proton Beam Irradiation Versus Conventional Radiation on Organs-at-risk in Stage II-III Breast Cancer Patients

Change in Left Ventricular Ejection Fraction (LVEF) Using Echocardiography

Comparison of the change in LVEF between conventional radiation and proton beam radiation groups. Reduced cardiac function is defined as an ejection fraction \<50%.

Time frame: Baseline, end of treatment (approximately 10 weeks), then 6, 12, 24, 36, and 60 months post treatment

Radiation-induced Lung Parenchymal Changes Using CT Imaging

Radiation-induced lung parenchymal changes will be assess with non-contrast enhanced computerized tomography (CT) scans and incidence will be estimated in each radiation group by the cumulative incidence function and compared using Gray's test. Among patients who do not have any changes detected, death and disease progression will be considered as competing risks.

Time frame: Baseline, 3,6,12, months post treatment

Incidence of Thyroid Dysfunction

Incidence of thyroid insufficiency will be estimated in each radiation group by the cumulative incidence function and compared using Gray's test. In the absence of thyroid dysfunction, death and disease progression will be considered as competing risks.

Time frame: Baseline, end of treatment (approximately 10 weeks), then 12, 24, 36, and 60 months post treatment

Incidence of Ipsilateral Arm Lymphedema

Incidence of ipsilateral arm lymphedema will be estimated in each radiation group by the cumulative incidence function and compared using Gray's test.