Expression of metabolic genes associated with changes in brain structure across the lifespan affects patients (pts) outcomes in metastatic colorectal cancer (mCRC): Data from CALGB/SWOG 80405 (Alliance).

3144 Background: Longitudinal brain structure changes across the lifespan are associated with neurodegenerative disorders. We previously showed that genetic variants in dopamine and Parkinson’s disease genes are predictive and prognostic in mCRC. Indeed, the brain-gut axis is emerging as a critical player in CRC biology. Hence, we investigated whether the tumor gene expression of 3 metabolic genes involved in brain development and aging could affect treatment response in patients enrolled in the CALGB/SWOG 80405 trial. Methods: 433 mCRC pts treated with either bevacizumab (bev, n = 226) or cetuximab (cet, n = 207) in combination with first-line chemotherapy were included in the analysis. RNA was isolated from FFPE tumor samples and sequenced on the HiSeq 2500 (Illumina). Overall survival (OS) and progression-free survival (PFS) were compared between groups of pts categorized by tertiles of expression of 3 genes: APOE, DACH1, and GPR139. Likelihood ratio tests, hazard ratios and 95% confidence intervals were computed from multivariate Cox proportional hazards models, adjusting for age, sex, ethnicity, ECOG PS, tumor location, number of metastatic sites, KRAS, MSI status, and treatment. Logrank P-values describe differences without adjustment for patient characteristics. Results: Both APOE and DACH1 (but not GPR139) met the 0.05 false discovery rate threshold for association with both PFS ( P = .00085, P = .015) and OS ( P = .021, P = .021, respectively) in the full Cox models. In cet-treated pts, APOE-high (H) showed significantly shorter PFS (median 9.2 vs 11.8 vs 13.0 months (mo), high vs low (as reference) logrank P = .0021) and OS (median 21.9 vs 35.8 vs 34.6 mo; logrank P = .0017) compared to APOE-median and -low, respectively. Opposite results were observed for DACH1, where DACH1-H tumors had longer PFS (median 14.5 vs 10.6 vs 8.07 mo; logrank P = .0011) and OS (median 39.4 vs 30.9 vs 21.5 mo; logrank P = .0021) when treated with cet. In bev-treated pts, similar results were observed with APOE-H showing shorter OS (median 25.8 vs 26.3 vs 37.5 mo; logrank P = .0016) and DACH1-H longer OS (median 36.5 vs 28.3 vs 22.4 mo; logrank P = .0017). No significant gene-treatment interaction was observed for either gene for PFS and OS. Conclusions: The tumor expression of metabolic genes associated with changes in the brain structure was prognostic in mCRC pts treated with first-line therapy. Notably, APOE and DACH1 have been recently reported to play a role in CRC where APOE overexpression has been associated with aggressive biological behavior whereas DACH1 has been shown to suppress CRC cell growth and invasion. Our results support this evidence and suggest that further investigation into the role of APOE and DACH1 in CRC biology and into their potential as targets for drug development is warranted. Trial Identifier: NCT00265850.