Study Comparing Two Types of Radiation Therapy for Early Stage Breast Cancer After Lumpectomy

Inclusion Criteria

• Diagnosed with early stage breast cancer, specifically Tis, T1, or T2 (tumor size 3.0 cm or smaller), with no spread to lymph nodes or other parts of the body.
• If the cancer is found in multiple small areas, the total size must be 3.0 cm or less.
• Clear surgical margins of at least 0.2 cm after surgery.
• Patients with certain types of breast cancer or high-grade DCIS must have an MRI to confirm the cancer is localized.
• Patients with DCIS must have had an MRI before their lumpectomy.
• Any suspicious findings on MRI outside the planned surgery area should be checked with an ultrasound and possibly a biopsy.
• Patients with cancerous calcifications on a mammogram must have another mammogram after surgery to ensure all calcifications are removed.
• Willing to undergo additional screening and meet the study's eligibility requirements.
• Successful placement of markers needed for image-guided radiation therapy.
• The planned treatment area should not exceed 25% of the affected breast.
• Radiation therapy should start within 10 weeks after surgery.

Exclusion Criteria

• Pregnant or breastfeeding women.
• Have a condition called collagen-vascular disease.
• Surgical margins less than 0.2 cm after surgery.
• Persistent cancerous or suspicious calcifications.
• Cancer spread to multiple areas or microscopic disease larger than 3.0 cm.