EMERALD: Endocrine Therapy oMission With Radiation in ER+ Breast Cancer: Assessing Quality of Life and Disease Control: a Prospective Phase II Trial

Inclusion criteria

• Diagnosis of pathologically-confirmed invasive breast cancer
• Age ≥ 60 years
• Treatment with breast conserving surgery
• Pathologic T stage of T1 or T2 with total tumor size ≤ 3cm including any component of DCIS that may exist in conjunction with invasive disease
• Ki-67 . 20% and/or Oncotype 0-10 (Ultra Low)
• Final surgical margins negative, defined as no tumor on ink. Lobular carcinoma in situ involving the final surgical margin will be disregarded.
• Tumor must be estrogen receptor positive, progesterone receptor positive and HER2Neu non-amplified as per current College of American Pathologists guidelines
• Clinical nodal stage cN0
• If pathologic nodal staging is obtained, then pN0 or pN0(i+)
• Patients have had or have a scheduled discussion with a breast medical oncologist regarding adjuvant treatment options
• Patients who have met criteria 4.1.1-4.1.9 who never initiate endocrine therapy OR who initiate adjuvant endocrine therapy but discontinue it within 6 months of initiation \* In some clinical scenarios, patients may have a particularly small volume of tumor, making it not be feasible for all of these biomarkers to be evaluated. In this scenario, if the PI and/or Protocol Collaborators are able to document that a patient is being treated as if they have luminal A (biologically favorable) breast cancer then the patient is eligible for enrollment if all other eligibility criteria are met.

Exclusion criteria

• Node positive disease (N1-3)
• Metastatic disease (M1)
• Grade 3 disease and lymphovascular space invasion in the tumor
• Synchronous bilateral breast cancer
• Receipt of neoadjuvant therapy
• Diagnosis of a collagen vascular disease associated with an increased incidence of radiation toxicities such as scleroderma or systemic lupus erythematosis
• Diagnosis of other cancer within the prior 5 years, excluding basal or squamous cell carcinoma of the skin that has been treated
• Patient with psychiatric illness/social situations that would limit compliance with study requirements
• Prior radiotherapy to the index breast or recurrent cancer of the breast
• Known carrier of a mutation associated with predisposition to breast cancer development, including BRCA1 or BRCA2