Single Pre-Operative Radiation Therapy - With Delayed or No Surgery (SPORT-DNS)

Inclusion criteria

• Female aged 50 years or older.
• Postmenopausal status (Defined as: age 60 OR bilateral ovariectomy OR amenorrhea > 12 months prior to breast cancer diagnosis without using oral contraceptives/hormone replacement therapy) (65).
• World Health Organization (WHO) performance status 0-2.
• Invasive ductal carcinoma proven by biopsy done ≤ 12 weeks from treatment start.
• Unifocal disease on preoperative staging ultrasound or MRI done ≤ 12 weeks from treatment start.
• Tumors less than or equal to 2cm clinically on physical exam, as well as on breast ultrasound.
• No clinical evidence of nodal disease (i.e. cN0), on physical examination done ≤ 12 weeks from treatment start, as well as on breast ultrasound.
• Estrogen receptor status (ER) positive on biopsy ≥ 80%.
• Progesterone receptor status (PR) positive on biopsy ≥ 20%.
• Her2 negative on biopsy.
• No lymphovascular invasion on biopsy.
• Low Oncotype DX recurrence score performed on biopsy specimen (RS ≤18).
• Planned surgery is a partial mastectomy with sentinel lymph node biopsy.

Exclusion criteria

• Age less than 50 years.
• Premenopausal or uncertain menopausal status.
• A known deleterious mutation in BRCA 1 and/or BRCA 2.
• Clinical tumor size > 2.0 cm in greatest diameter on staging ultrasound.
• Tumor histology limited to lobular carcinoma only.
• Clinically positive axillary nodes (cN+).
• Lymphovascular invasion on biopsy.
• Pure ductal or lobular carcinoma in situ on biopsy.
• Extensive intraductal component on biopsy.
• Neoadjuvant hormonal manipulation or chemotherapy.
• Prior non basal cell or squamous cell skin cancers within 5 years.
• More than one primary tumor in different quadrants of the same breast.
• Diffuse microcalcifications on mammography.
• Paget's disease of the nipple.
• Previous irradiation to the ipsilateral breast.
• Presence of an ipsilateral breast implant or pacemaker.
• Serious non-malignant disease (e.g. cardiovascular, pulmonary, systemic lupus erythematosus (SLE), scleroderma) which would preclude definitive radiation treatment.
• Estrogen receptor status (ER) not known.
• Currently pregnant or lactating.
• Psychiatric or addictive disorders which would preclude obtaining informed consent or adherence to protocol.
• Geographic inaccessibility for follow-up.
• Lack of preoperative staging with breast and axillary ultrasound.
• Inability to adequately plan the patient for the experimental technique.
• Prior breast cancer.