Primary Outcome Measures:
- Number of Adverse Events [ Time Frame: 5 years ]
The purpose of the APBI Proton Therapy study is to examine the feasibility, side effects, and clinical efficacy of using proton therapy on only the tumor bed of women being treated for breast cancer after surgical removal of malignancy (as opposed to whole breast treatment). The study's aim is to establish the effects of this type of therapy as it compares to both traditional radiation and whole breast treatment therapies. In order to be eligible, the patient must be a female older than 50 with either invasive ductal, medullary, papillary, colloid (mucinous) or tubular histologies of stage IA-IIA breast cancer, ECOG performance status of 0-2, have margins of greater than or equal to 2mm, be node negative or have only microscopic node disease, have estrogen- or progesterone-positive breast cancer, and other eligibility criteria must be met that is more detailed to describe herein.