STereotactic Body Radiotherapy (SBRT) for Oligoprogressive Breast Cancer

Inclusion criteria

• Diagnosis of progressive metastatic breast cancer on first line systemic therapy, including either hormone receptor positive, Her-2 negative (HR+/Her2-) on endocrine therapy + CDK4/6 inhibitor or Her-2 positive (hormone receptor positive or negative /Her2+) on Her2-targeted therapy regimens.
• Progressive disease limited to "oligoprogression", defined as progression of 5 or fewer extra-cranial lesions with otherwise controlled systemic disease on current line of systemic therapy.
• Patients must have previously controlled disease for at least six months on current systemic therapy
• Deemed a candidate for stereotactic body radiotherapy (SBRT) to all OP lesions

Exclusion criteria

• Requires change in systemic therapy line at the time of OP as determined by medical oncologist;
• Progression on 2nd line or subsequent lines of therapy
• Lacks CT or bone scan Imaging within previous 45 days;
• Progression in >3 sites in the liver or lung;
• Hormone positive disease on endocrine therapy only at time of enrollment;
• Previous radiotherapy to same site or vicinity preventing definitive SBRT (e.g. within 5 cm);
• Lesions deemed not amenable to SBRT due to large size or location;
• Unacceptable fracture risk according to clinician judgement for bone lesions;
• Brain metastasis or Spinal cord compression;
• History of major radiosensitivity syndrome or contraindications to radiotherapy.