Metastasis-Directed Stereotactic Body Radiation Therapy in Oligometastatic and Oligoprogressive Solid Malignancy: Outcomes and Effect on Systemic Treatment.

Purpose: To assess the clinical outcomes and evaluate Freedom from Introduction or Switching of Systemic Treatment (FISST) in patients with oligometastatic (OM) and oligoprogressive (OP) disease undergoing stereotactic body radiotherapy (SBRT).

Methods: The primary end points were FISST and local control (LC) rates of lesions that received SBRT. The secondary end point was overall survival (OS) after SBRT. To calculate FISST, event was defined as the need to introduce or switch the systemic line of treatment for any reason or inability to provide systemic treatment when needed because of poor performance status (PS) (Eastern Cooperative Oncology Group PS ≥3) or other reasons. OS was a secondary outcome.

Results: A total of 200 patients were included. The median age was 60 (IQR, 49-70) years. The most common primary tumors were colorectal (61, 30.5%), breast (30, 15.0%), lung (28, 14.0%), head and neck (23, 11.5%), and prostate (16, 8.0%). A total of 257 metastatic lesions were treated. Bone was the most frequent site (115, 44.7%), followed by the liver (55, 21.4%), lung (44, 17.1%), lymph nodes (25, 9.7%), and adrenal glands (11, 4.3%). The median follow-up was 15 months. FISST at 1 and 2 years were 52% and 39%, respectively. LC at 1 and 2 years were 86.3% and 80%, respectively. OS at 1 and 2 years were 76.5% and 64.8%, respectively. Grade III toxicity was reported in 1.5% of patients overall, with no observed grade IV or V toxicity.

Conclusion: SBRT is effective and safe for treating OM and OP solid cancers, prolonging FISST and potentially delaying systemic treatments, particularly in settings with limited access to advanced therapies.