Outcomes of Extracranial Oligorecurrence after Prior Metastases Directed Stereotactic Body Radiotherapy for Oligometastatic Disease

Abstract

<h3>Purpose/Objective(s)</h3> The Consortium of Oligometastatic Research (CORE) database consists of 1033 patients who presented with either synchronous or metachronous oligometastatic disease and were treated with ablative therapy to all sites. Of this cohort, a subset of patients had subsequent extracranial oligometastatic recurrence. These patients represent a unique cohort and we aim to report their outcomes in an effort to appropriately select patients who would benefit from further ablative therapy. <h3>Materials/Methods</h3> A retrospective review of patients in the CORE database was conducted. Oligorecurrent disease was defined as ≤5 new metastases after having previously received ablative treatment to all known sites of oligometastatic disease. Our primary endpoint was time to widespread progression (WSP), estimated using competing risk analysis where death was the competing risk. Widespread progression was defined as developing metastatic dissemination not amenable to further ablative treatment, inclusive of developing ≥6 new sites of extracranial metastases or a malignant effusion. WSP was measured from the date of initial diagnosis and from the date of first oligorecurrence. Secondary endpoint was estimated overall survival (OS) using Kaplan-Meier method. <h3>Results</h3> A total of 375 patients had oligorecurrent disease and 233 received further ablative therapy to all metastatic sites. Of the 233 patients, 83 had a subsequent oligorecurrent event and 57 received further ablative therapy to all metastases. Of the 375 patients, 161 developed widespread progression by last follow up. The median time to widespread progression from initial diagnosis was 80.7 months (95% CI: 68.2-90.9) and from first oligorecurrence was 55.1 months (95% CI: 33.3-not reached). The 2 year and 5-year WSP rates from initial diagnosis were 11.0% (95% CI: 7.6-14.3) and 40.6% (95% CI: 34.3-46.9) and from first oligorecurrence were 38.8% (95% CI: 33.6-43.9) and 52.5% (95% CI: 45.3-59.8). The median OS was 44.8 months (95% CI 37.0-51.0). The 1 year, 2 year and 5-year OS rates were 85.0% (95% CI: 81.9-89.1), 69.8% (95% CI: 64.9-74.6) and 33.3% (95% CI: 25.5-41.1) respectively. <h3>Conclusion</h3> Individuals who develop recurrence in a limited number of sites appear to represent a favorable subgroup of metastatic patients. In this retrospective cohort, oligorecurrent patients demonstrate favorable natural histories with regards to time to widespread progression and overall survival that may benefit from further metastases directed ablative therapy.