MACC1 expression as a candidate prognostic biomarker in colorectal cancer patients receiving adjuvant oxaliplatin-based therapy.

Abstract

567 Background: MACC1, part of the HGF-MET pathway, drives proliferation and regulation of MET expression in vitro. In vivo, MACC1 is associated with tumor progression and studies suggest greater MACC1 expression is associated with resistance to platinum-based chemotherapy. We hypothesized that MACC1 may be a prognostic biomarker in colorectal cancer (CRC). Methods: MACC1 expression was evaluated by immunohistochemistry on tumor microarrays (N = 428). Patients were stage I-III CRC who received an oxaliplatin-based regimen (either with 5-FU (FOLFOX) or capecitabine (XELOX)) within the HeCOG 6C/08 observational study. MACC1 expression was assessed by a blinded GI pathologist using a scale ranging from 0 (no staining) to 3+ (strong expression). Each patient had at least 3 samples and the strongest result was used for the final score. MACC1 positivity was defined as ≥2+ expression and 0-1+ as MACC1-. Cox regression models were used to estimate hazard ratios (HR) for the association of MACC1 expression with patient characteristics, disease-free (DFS), and overall survival (OS). Results: 400/428 CRC tumors were evaluable: 322 (80.5%) were MACC1+ and 78 (19.5%) MACC1-. Mucinous features were less likely in MACC1+ patients (24% vs. 38%, p = 0.02). Other unfavorable features including grade, lymphovascular invasion, perineural invasion, and tumor mutational burden were not significantly different. There was no difference for stage, microsatellite instability, BRAF, KRAS, or NRASstatus between MACC1+/- cancers. There was a trend towards worse survival in MACC1+ patients regardless of treatment (DFS HR 1.55 [95% CI: 0.87, 2.76], OS HR 1.59 [95% CI 0.74, 3.4]). This difference was not statistically significant for OS (p = 0.26) or DFS (p = 0.08) even when stratified by clinicopathologic variables. Conclusions: Patients with MACC1+ CRC tumors who received adjuvant oxaliplatin-based therapy were less likely to have mucinous histology. They had a trend toward independently worse survival that was not significant when accounting for stage and clinicopathologic variables. Studies focused on the predictive role of MACC1 and oxaliplatin in stage III CRC are in progress.