The purpose of this study is to determine if the dose of radiation therapy that is effective in producing a treatment response, delivered over a shorter treatment period, is a safe approach that causes few or mild side effects in women with newly diagnosed breast cancer or DCIS who have had a lumpectomy procedure.
Female
Age >/= 45 years
Unicentric pathological stage I (pT1 or T2 pN0_M0) invasive ductal breast cancer or DCIS measuring <3 cm in longest diameter on pathology and/or mammogram that is histologically confirmed. If T2, the tumor must be less than 3cm in longest diameter. Note: Women ≥ 70 years or older with T1 invasive ductal carcinoma who are estrogen- receptor positive (ER+) with clinically negative axillary nodes, and do not undergo surgical lymph node mapping or dissection (i.e., if tumor deposit is 0.2 mm or less, regardless of whether the deposit is detected by immunohistochemistry or hematoxylin and eosin staining) will also be eligible. Patients age 50 or older who are clinically node-negative by physical exam and ultrasound and have a primary tumor that is <=2 cm and hormone-receptor positive, are also eligible.
Histologically negative tumor margin or no tumor in a re-excision specimen on final shaved specimen.
Patients with distant metastasis
Patients who are pregnant or breastfeeding
Patients with diffuse (>1 quadrant or >5cm) suspicious microcalcifications or patients with known multicentric OR multifocal disease. (microscopic multifocal disease that may be unifocal and/or appear multifocal due to sectioning is allowed after review with PI).
Prior radiation therapy to the ipsilateral or contralateral breast or thorax.