Stereotactic Radiation Therapy in Colorectal Cancer Brain Metastasis: An International, Multicentric Cohort

Abstract

Colorectal cancer (CRC) is the third most common cancer in western countries, but brain metastases only occur in 1% of CRC patients. Overall survival in CRC patients rises as new systemic drugs became available. Thus the incidence of brain metastases in CRC patients will likely increase. We conducted a multicentric analysis to evaluate and compare the outcomes of stereotactic radiosurgery (SRS) and hypofractionated stereotactic radiotherapy (HFSRT) in CRC brain metastasis management. On behalf of the association of French-speaking neuro-oncologist (ANOCEF), we retrospectively collected individual data of patients treated with SRS or HFSRT for CRC brain metastases in 6 hospitals in France and Germany. The primary endpoint of the study was the radiological response rate defines as a complete response, partial response, or stability of the metastasis according to RANO BM criteria. The median follow-up from initial treatment was 31 months. The median response rate for metastasis treated was 65.9% (CI 95% [51.9% – 79.9%]) and was positively influenced by SRS whereas multiple brain metastases were related to poorest response rates as reported in the table below.Abstract 2188; Table 1ORSD2.5%97.5%p(OR<1)p(OR>1)Disease controlled0.730.510.172.050.790.21Multiple brain metastases0.720.520.162.050.800.20PTV volume (mL)0.990.030.941.040.700.30SRS3.274.120.3613.500.210.79 Open table in a new tab The median overall survival (OS) from initial treatment was ten months (CI 95% [5 – 22]). OS was negatively influenced by extra-cranial metastases, male gender, whereas it influenced positively by brain progression-free survival (BPFS). We report the results of one of the largest cohort of CRC brain metastasis treated with stereotactic radiotherapy. Our analysis suggests that age is associated with a higher response probability while the control of the disease is associated with a lower response probability. However, patients with a controlled disease are more likely to live longer and thus experience a progression of the treated metastasis. Finally, SRS seems to be associated with a higher response probability.