Hypothesis:

In selected women with node-negative invasive breast cancer treated with breast conserving surgery, postoperative accelerated partial breast irradiation (APBI) limited to the region of the tumour bed delivered by 3-dimensional conformal radiation therapy (3D CRT) is technically feasible and reproducible with acceptable treatment toxicity, cosmetic outcome, and local control rate in a multicentre trial.

This is a TROG multicentre feasibility study of APBI using 3D CRT in selected women with node-negative breast cancer treated by breast conserving surgery with negative margins.

This is a one-arm feasibility study in which the primary endpoint is the feasibility rate for APBI using 3D CRT. This is defined as the proportion of eligible patients treated without a major protocol deviation. Secondary endpoints include radiation toxicity, cosmetic outcome, quality of life, time to ipsilateral breast recurrence, disease-free survival, and overall survival.

Primary objectives: To evaluate the technical feasibility and reproducibility of APBI limited to the region of the tumour bed using 3D CRT following breast conserving surgery.

Secondary objectives:

• To assess the acute and long term toxicity of APBI using 3D CRT.
• To examine the cosmetic outcome of women with breast cancer treated by breast conserving surgery and APBI using 3D CRT.
• To determine the time to ipsilateral breast recurrence, disease free survival and overall survival of women with node-negative breast cancer completely resected by breast conserving surgery followed by APBI using 3D CRT.
• To assess the quality of life of women with node-negative breast cancer treated by breast conserving surgery and APBI using 3D CRT.

Inclusion Criteria:

Patients must fulfill all of the following criteria for admission to study:

• Women aged >= 50 years.

• Histologically confirmed diagnosis of invasive breast carcinoma of non-lobular histology.

• Bilateral mammograms performed within 6 months prior to registration.

• Treated with breast conserving surgery (primary excision or re-excision) with negative radial resection margins of >= 2 mm* for both the invasive and if present, associated intraductal tumour.

  *Patients with superficial or deep resection margin of < 2 mm are eligible if surgery has removed all of the intervening breast tissue from the subcutaneous tissue to the pectoralis fascia.

• Unifocal tumour measuring ≤ 20 mm in maximum microscopic dimension.

• Negative nodal status determined by sentinel node biopsy, axillary dissection, or for women > 70 years of age, clinical examination.

• No evidence of distant metastasis.

• Assessed by surgeon and radiation oncologist to be suitable for breast conserving therapy.

• Ability to tolerate protocol therapy.

• Protocol therapy must commence no later than 12 weeks from the last surgical procedure or 8 weeks from the last dose of chemotherapy.

• Availability for long-term follow-up.

• Women of child-bearing potential must use adequate contraception during RT.

• Written informed consent.

Exclusion Criteria:

Patients who fulfill any of the following criteria are not eligible for admission to study:

• Multifocal or multicentric tumours.
• Clinical or pathologic evidence of any of the following tumour features: extension to chest wall (excluding pectoralis muscle); oedema (including peau d'orange) or ulceration of skin; satellite skin nodules confined to the same breast; and inflammatory carcinoma.
• Presence of extensive intraductal component (ductal carcinoma in situ occupying > 25% of the primary invasive tumour and present adjacent to the primary tumour).
• Node-positive breast cancer determined by sentinel node biopsy, axillary dissection, or in women > 70 years of age, clinical examination.
• Inability to localise surgical cavity on CT scans with no evidence of a surgical cavity, seroma or surgical clips delineating the tumour bed.
• Treatment target volume estimated to occupy > 25% of the ipsilateral whole breast volume.
• Synchronous or metachronous bilateral invasive or intraductal breast cancer.
• Locally recurrent breast cancer.
• Ipsilateral breast implant.
• Serious non-malignant disease that precludes definitive surgical or radiation treatment (e.g. scleroderma, systemic lupus erythematosus, cardiovascular/pulmonary/renal disease).
• Previous or concomitant malignancies except non-melanoma skin cancer, carcinoma in situ of the cervix, and invasive carcinoma of the colon, thyroid, cervix, or endometrium treated five years prior to study entry.
• Women who are pregnant or lactating.
• Psychiatric or addictive disorders that preclude obtaining informed consent or adherence to protocol