DNA hypermethylation as a predictor of extramural vascular invasion (EMVI) in rectal cancer.

PURPOSE

DNA hypermethylation in gene promoter regions (CpG islands) is emerging as an important pathway in colorectal cancer tumourigenesis. Whilst genetic mutations have been associated with extramural vascular invasion (EMVI) in rectal cancer, no such association has yet been made with epigenetic factors.

METHODS

100 consecutive neoadjuvant-naïve patients undergoing curative surgery for rectal were classified according to the presence or absence of EMVI on histopathological examination. DNA was extracted from tumours and subjected to bisulfite conversion and methylation-specific PCR to determine CIMP status (high, intermediate, or low; according to a validated panel of 8 genes). CIMP status was correlated with EMVI status, histopathological, clinical, and demographic variables, in addition to overall (OS) and disease free (DFS) survival.

RESULTS

51 patients were characterised as CIMP-low, 48 CIMP-intermediate, and one patient CIMP-high. EMVI-positivity was associated with CIMP-intermediate epigenotype (p < 0.001). Patients with EMVI-positive tumours were found to have significantly more advanced disease by pT, pN, and pAJCC categorisation (p = 0.002, p < 0.001, and = p < 0.001, respectively). EMVI-positivity was significantly associated with the requirement for adjuvant chemotherapy (p < 0.001), and worse DFS but not OS (p = 0.012 and p = 0.052).

CONCLUSIONS

Given the association between CIMP-intermediate epigenotype and EMVI-positivity, and the subsequent disadvantage in pathological stage, requirement for adjuvant therapy and worse survival, tumour epigenotyping could potentially play an important role in personalising patients' cancer care. Further work is required to understand the mechanisms that underlie the observed effect, with the hope that they may provide novel opportunities for intervention and inform treatment decisions in rectal cancer.