First-line anti-EGFR or anti-VEGF therapy, tumour sidedness, and survival: Results from the South Australian (SA) Metastatic Colorectal Cancer (mCRC) Registry.

Abstract

42 Background: The anti-EGFR monoclonal antibodies panitumumab (Pmab) and cetuximab (Cmab) and the anti-VEGF antibody bevacizumab (bev) have demonstrated clinical efficacy in mCRC in combination with first-line chemotherapy. Clinical and molecular characteristics, such as primary tumour sidedness, RAS, BRAF and MMR status are prognostic and predictive biomarkers for response to treatment. Our aim was to compare the survival and tumour characteristics of patients receiving first-line chemotherapy and antibody combinations using the SA mCRC Registry. Methods: This real-world registry has collected data from all patients diagnosed with mCRC in SA prospectively since 2006. We identified patients who had received first-line Pmab, Cmab or bev. Survival was analysed using the Kaplan-Meier method and log-rank test to compare outcomes based on primary tumour location. Results: Of the 5537 patients currently entered onto the registry, 1313 with RAS results available had received first-line anti-EGFR/VEGF antibodies and had colon tumour side recorded. The table summarises median overall survival (mOS) and patient characteristics. Survival was significantly shorter for those with right colon cancers (P < 0.001). There were more high-grade (P < 0.001), KRAS mutant (P = 0.004) and BRAF mutant (P = 0.036) tumours in those with right colon cancers, and a trend towards fewer curative liver resections (P = 0.059). There was no significant difference in mOS seen between Pmab, Cmab or bev for both left (P = 0.14) and right-sided (P = 0.88) primary tumours. Conclusions: There were more high-grade, BRAF and KRAS mutant patients with right colon tumours, and lower rates of liver resection, which may explain the significantly shorter mOS. The survival seen for Pmab and Cmab was almost identical for both right and left primary tumours. When comparing Pmab, Cmab and bev as first-line therapy, there was no significant difference in mOS for both left- and right-sided CRC. [Table: see text]