Radiation Therapy in Women With Low Risk Early-Stage Breast Cancer Who Have Undergone Breast Conservation Surgery

RATIONALE: Radiation therapy uses high-energy x-rays to kill tumor cells. Giving radiation therapy after surgery may kill any tumor cells that remain after surgery. It is not yet known whether intensity-modulated radiation therapy is more effective than standard radiation therapy in treating patients with early-stage breast cancer.

PURPOSE: This randomized phase III trial is comparing radiation therapy regimens in treating women with early-stage breast cancer who have undergone breast-conservation surgery.

OBJECTIVES:

* To test partial breast radiotherapy using intensity-modulated techniques following complete local tumor excision in women with low-risk, early stage breast cancer.

OUTLINE: This is a multicenter study.

Patients are stratified according to center (not participating in sub-studies vs participating in sub-studies). Patients are randomized to 1 of 3 treatment arms.

* Arm I (control): Patients undergo standard whole breast radiotherapy once daily on days 1-5 (15 fractions) for 3 weeks.
* Arm II: Patients undergo reduced whole breast radiotherapy (15 fractions) and standard partial breast radiotherapy (15 fractions) once daily on days 1-5 for 3 weeks.
* Arm III: Patients undergo standard partial breast radiotherapy once daily on days 1-5 (15 fractions) for 3 weeks.

All patients complete a family history questionnaire at baseline. Patients also undergo blood sample collection at baseline and paraffin-embedded tissue collection at follow-up for molecular studies analyzing inter-patient variation by microarrays.

Patients in centers participating in sub-studies undergo quality of life and health economic assessment at baseline, 6 months, and 1, 2, and 5 years. These patients also undergo photographic assessment at baseline, 2 years, and 5 years.

After completion of study treatment, patients are followed for 10 years.

Eligibility Criteria:
DISEASE CHARACTERISTICS:

* Diagnosis of low-risk early stage breast cancer, meeting the following criteria:

  * Invasive adenocarcinoma

    * No invasive carcinoma of classical lobular type
    * lympho-vascular invasion present or absent
  * Tumor size pathologically determined to be ≤ 3.0 cm in diameter (pT1-2) (\< 3.1 cm maximum microscopic diameter of invasive component)
  * Unifocal disease
  * Grade I, II, or III disease
  * Axillary lymph nodes negative or 1-3 nodes positive (pN0 or pN+(1-3))
* Must have undergone breast conservation surgery with or without adjuvant systemic therapy

  * Minimum microscopic margin of non-cancerous tissue ≥ 2 mm (excluding deep margin if this is at deep fascia)
* At low risk of local recurrence after radiotherapy (\< 1% annual risk local recurrence)
* No prior mastectomy
* No blood-borne metastases

PATIENT CHARACTERISTICS:

* No prior malignancy except nonmelanoma skin cancer

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* No prior endocrine therapy or chemotherapy

  * Neoadjuvant endocrine therapy allowed provided the tumour is \< 3.0 cm and all other inclusion criteria are met
  * No primary endocrine therapy as a replacement for surgery
* No concurrent chemoradiotherapy