Stereotactic Ablative Radiotherapy for OligoMetastatic Breast Cancer

Inclusion criteria

• Histologically or cytological confirmed recurrent OMBC.
• Age ≥18 years old.
• OMBC defined as 1-5 metastases in a maximum of two organs confirmed by PET-CT.
• Patients already on 1st line systemic treatment can be enrolled if repeated tumour evaluations show stable disease.
• Patients with de novo stage IV OMBC must have a controlled primary tumour regardless of primary surgery or primary systemic treatment.
• Patients with local recurrence and OMBC must have a controlled local recurrence.
• ECOG/WHO 0-2.
• Life expectancy \> 6 months.
• Known ER, PgR and HER2 status of either primary tumour or metastasis (preferred).
• If measurable lesions, each ≤ 5 cm.
• Symptomatic bone metastases are allowed if ablative therapy can be delivered (femoral metastasis not allowed).
• Adequate organ function for the planned treatment according to local guide-lines.
• For patients with liver metastasis:
• No cirrhosis or hepatitis
• Hepatic function:
• Total bilirubin level \< 3.0 x institutional ULN
• ALT, AST, GGT, and alkaline phosphatase levels \< 3.0 x institutional ULN
• Albumin \> 2.5 mg/dL
• Metastasis not adjutant to stomach or small bowel.
• For patients with abdominal metastases: adequate renal function with a calculated creatinine clearance of \> 60mL/min.
• Toxicities from previous adjuvant therapies (excluding alopecia) must have recovered to grade 1 (defined by CTCAE 5.0). Stable grade 2 peripheral neuropathy are considered individually by the investigator.
• Negative pregnancy test within 14 days prior to start of treatment\*.
• If childbearing potential, willing to use an effective form of contraception\*.
• No other malignancy during the last 5 years except for radically treated basal or squamous cell carcinoma of the skin or CIS of the cervix.
• Signed informed consent and willingness to follow the trial procedures.

Exclusion criteria

• \> 1 line of systemic treatment for OMBC due to previous progressing disease (previous treatment of isolated local recurrences with a 2nd adjuvant treatment not included).
• Oligometastases in brain.
• Malignant pleural effusion or ascites.
• Metastasis growth that involves \> 3 vertebra and adjacent spinal cord, spine instability or neurological deficit resulting from compression, 25% spinal canal compromise or progressive neurological deficit.
• Unable to undergo imaging by either CT scan or MRI.
• Evidence of any other medical conditions (such as psychiatric illness, infectious diseases, neurological conditions, physical examination or laboratory findings) that may interfere with the planned treatment or affect patient compliance.
• Pregnancy or breast-feeding.
• Concurrent malignancy requiring therapy (excluding non-invasive carcinoma or carcinoma in situ).