Stereotactic Body Radiotherapy in Patients With Rare Oligometastatic Cancers (OligoRARE)

Each lesion may be treated with 1, 3, or 5 SBRT fractions of 16-24 Gy, 24-33 Gy or 25-40 Gy, respectively, depending on the local practice and size \& location of oligometastases. Three-fraction regimens will deliver a fraction every second day, and five-fraction regimens are delivered daily. All treatments must be completed within 2 weeks (10 working days) in order to avoid delays in starting systemic therapy.

Radiotherapy for patients in the standard arm should follow the principles of palliative radiotherapy as per the individual institution, with the goal of alleviating symptoms or preventing imminent complications. Recommended dose fractionations in this arm will include 8 Gy in 1 fractions, 20 Gy in 5 fractions, and 30 Gy in 10 fractions. Patients in this arm should not receive stereotactic doses or radiotherapy boosts, unless there is a clearly known clinical benefit (e.g. stereotactic radiation to a new brain metastases when all disease is controlled on systemic therapy).