Radiation Therapy in Treating Patients With Stage 0-II Breast Cancer

Inclusion Criteria:

Women who satisfy all of the following conditions are the only patients who will be eligible for this study.

1. The patient must consent to be in the study and must have signed an approved consentform conforming with federal and institutional guidelines.

2. Patients must be >/= 18 years old. (Adenocarcinoma of the breast is not seen inchildren)

3. English and non-English speaking patient

4. The patient must have stage 0, I, or II breast cancer. If stage II, the tumor sizemust be 3 cm or less.

5. On histological examination, the tumor must be DCIS or invasive adenocarcinoma ofthe breast.

6. Surgical treatment of the breast must have been lumpectomy. The margins of theresected specimen must be histologically free of tumor (DCIS and invasive). Re-excision of surgical margins is permitted.

7. Gross disease must be unifocal with pathologic (invasive and/or DCIS) tumor size 3cm or less. (Patients with microscopic multifocality are eligible as long as totalpathologic tumor size is 3 cm or less.)

8. Patients with invasive breast cancer are required to have axillary staging which caninclude sentinel node biopsy alone (if sentinel node is negative), sentinel nodebiopsy followed by axillary dissection or sampling with a minimum total of 6axillary nodes (if sentinel node is positive), or axillary dissection alone (with aminimum of 6 axillary nodes). Axillary staging is not required for patients withDCIS.

9. The target lumpectomy cavity must be clearly delineated and the target lumpectomycavity/whole breast reference volume must be < 30% based on thepostoperative/pre-enrollment CT scan.

10. Patients are eligible if, based on the postoperative CT scan, PBI is judged to betechnically deliverable.

11. Patients with a history of non-breast malignancies are eligible if they have beendisease-free for 5 or more years prior to enrollment and are deemed by theirphysician to be at low risk for recurrence. Patients with the following cancers areeligible if diagnosed and treated within the past 5 years: carcinoma in situ of thecervix, carcinoma in situ of the colon, melanoma in situ, and basal cell andsquamous cell carcinoma of the skin.

Exclusion Criteria:

Women with one or more of the following conditions also are ineligible for this study.

1. Men are not eligible for this study.

2. Individuals that are considered to be cognitively impaired.

3. T2 (> 3.0 cm), T3, stage III, or stage IV breast cancer.

4. More than 3 histologically positive axillary nodes.

5. Axillary nodes with definite evidence of microscopic or macroscopic extracapsularextension.

6. Palpable or radiographically suspicious ipsilateral or contralateral axillary,supraclavicular, infraclavicular, or internal mammary nodes at time of enrollmentunless there is histologic confirmation that these nodes are negative for tumor.

7. Suspicious microcalcifications, or densities (in the ipsilateral or contralateralbreast as documented on mammogram or breast ultrasound) unless biopsied and found tobe benign.

8. Non-epithelial breast malignancies such as sarcoma or lymphoma.

9. Proven multicentric carcinoma (invasive cancer or DCIS) in more than one quadrant orseparated by 4 or more centimeters.

10. Paget's disease of the nipple.

11. Synchronous bilateral invasive or non-invasive breast cancer.

12. Surgical margins that cannot be microscopically assessed or are positive atpathologic evaluation. (If surgical margins are rendered free of disease byre-excision, the patient is eligible.)

13. Clear delineation of the extent of the target lumpectomy cavity not possible.

14. Treatment plan that includes regional nodal irradiation.

15. Prior radiation to the index breast

16. Documented diagnosis of collagen vascular disease, specifically dermatomyositis witha CPK level above normal or with an active skin rash, systemic lupus erythematosis,or scleroderma.

17. Pregnancy or lactation at enrollment.

18. Women of reproductive potential must agree to use an effective non-hormonal methodof contraception during therapy.