Negative prognostic impact of Co-mutations in TGFß and TP53 pathways in surgically resected rectal tumors following neoadjuvant chemoradiotherapy.

ABSTRACT

BACKGROUND: Preoperative neoadjuvant chemoradiotherapy (nCRT) followed by total mesorectal excision (TME) is a common approach for treating patients with locally advanced rectal cancer. Nevertheless, the mutational profile and its prognostic impact in surgically resected tumor specimens after nCRT remains to be clarified. METHODS: The comprehensive analysis of mutational landscape was retrospectively conducted by target regions sequencing approach that covered 150 tumor-related genes. Univariate and multivariate logistic regression and Cox regression was used to examine the association of mutation status in genes and pathways with pathological response and prognosis. Data from Memorial Sloan Kettering Cancer Center (MSK) cohort was used for comparison with our results. RESULTS: The top five commonly mutated genes in resected rectal tumor tissue samples following nCRT were TP53 (42%), APC (31%), KRAS (27%), PIK3CA (14%) and FBXW7 (11%). Mutations in the WNT pathway, which was mainly represented by APC mutation, were found to be significantly associated with tumor regression grade (TRG) 3. In our cohort, co-mutations in the receptor tyrosine kinase (RTK)/RAS and WNT pathways were found to be independently associated with reduced risk of recurrent and significantly associated with longer disease-free survival (DFS). In both our cohort and the MSK cohort, co-mutations in the TGF-ß and TP53 pathways were significantly associated with worse DFS. CONCLUSIONS: Resected rectal tumor samples from patients without complete pathological response can be appropriately used to detect mutations. Co-mutations in the TGF-ß and TP53 pathways may provide more prognostic information beyond commonly used clinical factors.