Partial Breast Irradiation Using Interstitial Permanent Palladium-103 Seed Implant

25 women with low stage (pT1pN0) breast cancer, grade 1 or 2, will be accrued for adjuvant partial breast radiotherapy using PBSI and prospectively followed for 5 years. The primary aims is to evaluate implant quality according to recognized dosimetric parameters. Secondary aims include elaboration of approaches to different technical scenarios imposed by variation in seroma size, shape and location within the breast (expanding the technical manual to include recommended approaches to implants in different sectors of the breast and in different size breasts), incorporation of the use of live 3D ultrasound in the procedure (as opposed to current use of 2D US), assessment of patient acceptance and quality of life, physician assessment of cosmesis, assessment of toxicity, and recording of cost to the patient and health care system compared to alternate forms of breast radiotherapy.

Inclusion criteria

• Patient consent and signature of approved consent form.

• Age greater than 55 years and postmenopausal.
• Life expectancy of at least ten years
• Stage 0 or I breast cancer. Tumour size < 2 cm.
• Invasive cancer must be pathologic grade 1 or 2
• Histology must be either Ductal Carcinoma In Situ or invasive ductal adenocarcinoma of the breast.
• Tumour removed by lumpectomy with clear margins (DCIS and invasive).
• Unifocal disease
• For invasive breast cancer, axillary staging by either sentinel node biopsy or axillary dissection (minimum of 6 axillary nodes). Not required for DCIS.
• Brachytherapy generally should be performed within 16 weeks of the last surgery (lumpectomy, re-excision of margins, or axillary staging procedure). If > 16 weeks, will be assessed on case-by-case basis, based on seroma visibility and the presence of surgical clips in the tumour bed.
• Tumour must be Estrogen Receptor positive.
• The lumpectomy cavity (seroma) must be clearly delineated by ultrasound and CT and should be < 3 cm diameter (equivalent sphere) resulting in a maximum of 125 cc planning target volume (PTV).
• Breast seed implant must be considered technically deliverable by interstitial brachytherapy by the attending radiation oncologist and must be a minimum 2-plane implant.
• If prior non-breast malignancies, must have been disease-free for 5 or more years. Time limit waived for carcinoma in-situ of the cervix or colon, melanoma in-situ, and basal or squamous cell carcinoma of the skin.

Exclusion criteria

• Stage T2 or higher breast cancer

• Histologically positive axillary nodes.
• High grade (grade 3) invasive ductal carcinoma
• Extensive DCIS
• Lymphatic or Vascular Invasion positive
• Significant persistent post surgical complications
• Palpable or radiographically suspicious ipsilateral or contralateral axillary, or regional nodes, unless histologically confirmed negative.
• Suspicious microcalcifications, densities, or palpable abnormalities in the ipsilateral or contralateral breast unless confirmed benign.
• Proven multi-centric carcinoma (invasive cancer or DCIS)
• Paget's disease of the nipple.
• Synchronous bilateral invasive or non-invasive breast cancer.
• History of previous ipsilateral invasive breast cancer or DCIS.
• Surgical margins that are positive or cannot be microscopically assessed.
• Clear delineation of the target lumpectomy cavity not possible.
• Breast implants.
• Prior ipsilateral breast or thoracic radiotherapy.
• Known genetic mutation in Breast Cancer Associated (BRCA 1 or 2)
• Collagen vascular disease,