SBRT in oligometastatic disease of colorectal cancer

Abstract

INTRODUCTION.Throughout the recent years, stereotactic body radiotherapy (SBRT) has emerged as an effective, local therapy for treating limited (oligo) metastatic disease. This study presents characteristics and clinical outcomes of patients diagnosed with oligometastatic colorectal cancer who were treated with SBRT in an academic, specialized center. METHODS. A retrospective analysis was conducted on patients with oligometastatic disease, defined by ≤5 metastases, of colorectal origin treated with SBRT between 2017 and 2023. Patients were classified according to the oligo classification of the ‘OligoCare’ project; considering a history of (poly/oligo)metastatic disease prior to the present diagnosis of oligometastases, current treatment and corresponding response. The oligoclassifications, tumor- and radiation characteristics were examined. Primary outcome was 1-year overall survival (OS) and progression free survival (PFS), while the secondary outcome covered local control rate. RESULTS. A total of 175 patients with oligometastatic colorectal metastases were included. Majority of patients suffered from ‘repeat oligorecurrence’ disease, in which patients suffered from recurrent oligometastatic disease during a systemic-free interval. The OS was most favorable in patients diagnosed with this classification of ‘repeat oligoprogression’. ‘Metachronous oligorecurrence’, diagnosed with de novo oligometastases six months after primary cancer diagnosis, yielded best PFS rates. A history of polymetastatic disease gained worst survival rates. Metastases were found predominantly in the lungs, this also being the site most frequently irradiated and related to best survival outcomes. Metastases in more than two organ systems resulted in worse survival. Local control was achieved in 92.3%. High equivalent dose (>120 Gy) presented lower progression rates. CONCLUSION. Implementation of SBRT for oligometastatic colorectal cancer yielded favorable survival rates in patients without a history of polymetastatic disease prior to the diagnosis of oligometastatic disease. Compared to patients with more than two organ systems involved, these current metastases in one or two organ systems resulted improved survival, specifically pulmonary metastases. Higher equivalent radiation dose seems to result in less progression rates.