Radiation Therapy With or Without Trastuzumab in Treating Women With Ductal Carcinoma In Situ Who Have Undergone Lumpectomy

This randomized phase III trial studies radiation therapy to see how well it works with or
without trastuzumab in treating women with ductal carcinoma in situ who have undergone
lumpectomy. Monoclonal antibodies, such as trastuzumab, can block tumor growth in different
ways. Some block the ability of tumor cells to grow and spread. Others find tumor cells and
help kill them or carry tumor-killing substances to them. Radiation therapy uses high-energy
x-rays to kill tumor cells. It is not yet known whether radiation therapy is more effective
with or without trastuzumab in treating ductal carcinoma in situ.