External-Beam Partial-Breast Irradiation for Early Breast Cancer 40 Gy QD Over 2 Weeks

Standard therapy for patients with early stage breast cancer consists of surgery to remove the cancer followed by radiation therapy. One question regarding radiation therapy for early stage breast cancer is whether the entire breast needs to be radiated or only a more limited area surrounding the tumor. Whole-breast irradiation (WBI) is radiation therapy given to the whole breast. Partial-breast irradiation (PBI) is radiation therapy given only to the area of the breast where the cancer was removed (called the "tumor bed").

The investigators hope the option of PBI will reduce side effects from radiation therapy and shorten the radiation treatment process when compared to WBI, since only part of the breast is being treated. The investigators also hope that this will make such treatment more convenient for breast cancer patients.

The purpose of the study is to evaluate the the safety of external-beam PBI in selected early breast cancer patients utilizing PBI in ten daily fractions over two weeks. The investigators will also evaluate the local control and the cosmetic results.

After signing the consent form, the following will be assessed.

-CT scan of the breast that had the cancer removed to help plan the radiation therapy. This is referred to as a CT-simulation. This scan is done routinely as part of the regular treatment.

PBI Study Treatment: You will be given PBI once daily over 10 treatment days (Mon-Fri) over a 2 week period. During this time you will have a weekly interview, physical examination, and your skin will be assessed for any side effects of the radiation.

PBI will begin between 4 weeks to 3 months after breast surgery or 2-6 weeks after chemotherapy (if you have been given chemotherapy).

After the final dose of the study:

You will have the following scheduled follow-up visits: one at the completion of the radiation, once or twice during weeks 3-9 after the completion of radiation, once every 6 months for five years, and then once every year for the following five years after the completion of radiation therapy.

Eligibility Criteria:
Inclusion Criteria:

* Unicentric Stage I invasive ductal breast cancer or Grade I or II DCIS measuring less than or equal to 2cm on pathology and/or mammography
* Histologically negative tumor margin 2 mm or more from any inked edges, or no tumor in a re-excision specimen or final shaved specimen
* Clips must be placed in the lumpectomy cavity at the time of final excision in order to aid in the delineation of the tumor cavity at the time of simulation and radiation delivery

Exclusion Criteria:

* No distant metastasis
* Not pregnant or breastfeeding
* No diffuse suspicious microcalcifications
* No prior radiation therapy to the ipsilateral or contralateral breast or thorax
* No histologic evidence of lymphovascular invasion (LVI)
* No histologic evidence of EIC
* No history of cosmetic or reconstructive breast surgery
* No psychiatric illness that would prevent the patient from giving informed consent
* No medical conditions that, in the opinion of the treating physician would make this protocol unreasonably hazardous for the patient
* No other currently active second malignancy other than non-melanoma skin cancers