Retrospective Cohort Study of Oligometastatic and Oligoprogressive Malignancy Treated With Stereotactic Body Radiation Therapy (SBRT) With Intent to Delay New Systemic Therapy.

Abstract

PURPOSE/OBJECTIVE(S)\nUse of local therapy such as stereotactic body radiation therapy (SBRT) to treat oligometastatic malignancy is a well-established paradigm, but whether benefit extends to the oligoprogressive setting remains unclear. We present our institutional series of patients with oligometastatic or oligoprogressive malignancy treated with SBRT.\n\n\nMATERIALS/METHODS\nWe performed a retrospective study of patients with oligometastatic and oligoprogressive malignancy treated with SBRT between 2014 and 2019. Oligometastatic patients were defined as those with five or fewer metastatic lesions in total. Oligoprogressive patients were defined as those with more than five and up to twenty metastatic lesions in total, of which five or fewer metastases were progressing on current systemic therapy. Patients lacking complete treatment records or follow-up imaging were excluded. The study was approved by the NYU Institutional Review Board.\n\n\nRESULTS\nA total of 114 patients were treated with 123 courses of SBRT, of which 96 treated oligometastasis and 27 treated oligoprogression. Primary sites of disease included lung (38%), prostate (20%), and GI (12%), as well as gynecologic, abdominal, and cutaneous malignancies. Median follow-up was 21 months. No grade 3 or higher radiation-related adverse events were reported. Patients with oligometastatic malignancy had longer 2-year overall survival (79% vs 59%; P\u202f=\u202f0.003), local control (73% vs 55%; P\u202f=\u202f0.01), and progression-free survival (26% vs 8%; P < 0.001), but similar freedom from new systemic therapy (36% vs 31%; P\u202f=\u202f0.8). This result held true in subgroup analysis regardless of lung vs non-lung primary site, and regardless of the presence or absence of a targetable mutation.\n\n\nCONCLUSION\nIn this hypothesis-generating retrospective cohort study, patients with oligoprogressive malignancy treated with SBRT have similar freedom from new systemic therapy to patients with oligometastatic malignancy, strengthening the rationale for treating oligoprogressive malignancy with SBRT.