Treatment of metastatic breast cancer by stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS).

Background and purpose: The role of local ablative radiotherapy (stereotactic body radiotherapy (SBRT)/stereotactic radiosurgery (SRS)) in the management of metastatic breast cancer (mBC) patients remains unclear. This study aimed to assess the efficacy of SBRT/SRS in oligometastatic and oligoprogressive breast cancer patients. Methods: Totally 80 mBC patients with oligometastatic disease (OMD) and 80 with oligoprogressive disease (OPD) to ≤5 metastatic lesions were retrospectively analyzed. The endpoint was overall survival and progression-free survival, and univariate and multivariate analyses were performed for survival analysis. Results: Totally 160 mBC cases (80 OMD and 80 OPD cases) were analyzed, with a total of 291 treated metastases. In the study of OMD, we analyzed 30 cases with oligo-recurrence and 50 cases with sync-oligometastases. The median follow-up time was 46 months, and 1-, 2-, and 3-year OS rates for all patients were 89.8%, 77.6%, and 67.3%, respectively, and the 1-, 2-, and 3-year PFS rates were 71.4%, 44.9%, and 34.7% respectively. In multivariate analysis (MVA), treatment for oligometastases and non-triple-negative status predicted favorable OS. In patients with oligometastases, median OS was 58 months, and 1-, 2-, and 3-year OS rates were 100%, 91.7%, and 83.3%, respectively; median OS in patients with oligoprogression was 35 months, and 1-, 2-, and 3-year OS rates were 80%, 64%, and 52%, respectively. In mBC cases with limited brain metastases administered SRS, poor OS was detected in patient age under 45 years (P = 0.041), triple-negative cases (P = 0.025), and those with OPD (P = 0.022). In OMD, a significant improvement in PFS was observed in the oligo-recurrence group compared to the sync-oligometastases group (P = 0.013). Conclusion: Patients administered local ablative radiotherapy (SBRT/SRS) for oligometastases have better overall survival than those treated for oligoprogression. SBRT/SRS may be beneficial for young and non-triple-negative mBC cases. The presence of oligo-recurrence can predict a favorable prognosis of oligometastases in patients with mBC treated with SBRT/SRS. [ABSTRACT FROM AUTHOR]