Stereotactic Body Radiation Therapy for Oligometastatic Breast Cancer: A Retrospective Multicenter Study

Abstract

IntroductionStereotactic radiotherapy may improve the prognosis of oligometastatic patients. In the literature, there is very little data available that is specific to breast cancer.Materials and MethodsWe conducted a multicenter retrospective study. The primary objective was to estimate progression-free survival after stereotactic body radiotherapy (SBRT) using Cyberknife of breast cancer oligometastases. The secondary objectives were to estimate overall survival, local control, and toxicity. The inclusion criteria were oligometastatic breast cancer with a maximum of five lesions distributed in one to three different organs, diagnosed on PET/CT and/or MRI, excluding brain metastases and oligoprogressions. This was combined with systemic medical treatment.FindingsForty-four patients were enrolled from 2007 to 2017, at three high-volume cancer centers. The patients mostly had one to two lesion(s) whose most widely represented site was bone (24 lesions or 44.4%), particularly in the spine, followed by liver (22 lesions or 40.7%), then pulmonary lesions (six lesions or 11.1%). The primary tumor expressed estrogen receptors in 33 patients (84.6%); the status was HER2+++ in 7 patients (17.9%). The median dose was 40 Gy (min-max: 15-54) prescribed at 80% isodose, the median number of sessions was three (min-max: 3-10). The median D50% was 42 Gy (min max 17-59). After a median follow-up of 3.4 years, progression-free survival (PFS) at one year, two years, and three years was 81% (95% CI: 66-90%), 58% (95% CI: 41-72%), and 45% (95% CI: 28-60%), respectively. The median PFS was 2.6 years (95% CI: 1.3 – 4.9). Overall survival at three years was 81% (95% CI: 63-90%). The local control rate at two and three years was 100%. Three patients (7.3%) experienced G2 acute toxicity, no grade ≥3 toxicity was reported.ConclusionThe PFS of oligometastatic breast cancer patients treated with SBRT appears long, with low toxicity. Local control is high. SBRT for oligometastases is rarely applied in breast cancer in light of the population in our study. Phase III studies are ongoing.

Oligometastatic Breast Cancer Patients Treated with High-Dose Chemotherapy and Targeted Radiation: Long-Term Follow-Up of a Phase II Trial

“…Prospective data for SBRT in oMBC are available in a Phase II trial by Trovo et al, wherein, at a median of 30 month follow-up, 2-year PFS and OS were 53% and 95%, respectively, with no grade ≥3 toxicity [ 22 ]. These early results are consistent with other smaller or retrospective cohorts [ 23 , 24 , 25 , 26 , 27 , 28 ]. Given what is now known about SBRT based on SABR-COMET, NRG-BR001, and smaller single-arm studies, our long-term results may potentially be improved by combining state-of-the-art systemic therapy in combination with SBRT for oligometastatic disease.…”

Systemic Therapy Combined with Locoregional Therapy Improved Survival in Oligometastatic Breast Cancer: A Single-Center Retrospective Cohort Study

“…Lemoine et al pointed out that the median PFS of OMBC treated with stereotactic body radiation therapy appeared longer with low toxicity. The local control rate was 100% at three years [ 13 ]. Research carried out by Wijetunga et al also reported that long-term systemic disease control and survival could be achieved with stereotactic ablative body radiotherapy (SABR) for OMBC [ 14 ].…”