Introduction The presence of extramural vascular invasion (EMVI) has been associated with reduced survival in colorectal cancer (CRC), and failure to consider it may account for discrepancies in outcome between similar stages. One clinically and pathologically heterogeneous subtype of CRC is T4 disease. At the microscopic level, some tumours are classed as pT4a due to invasion of local organs, while others are defined as pT4b due to invasion of the visceral peritoneum (based on 5th edition of TNM). The aim of the present study was to compare T4a and T4b colorectal cancers for EMVI status and longterm outcome.
Methods Pathological data on consecutive cases of T4 colorectal cancer proceeding to surgery were extracted from a prospectively collected database between 2004 and 2011. Pathological parameters analysed included macroscopic tumour details, differentiation, nodal status, and the presence of EMVI. Patient demographics, disease stage, and longterm oncological outcomes were evaluated in all cases.
Results 276 consecutive cases of T4 colorectal cancer were identified during the study period. 92% of tumours were colonic and 8% rectal. 79% of tumours were T4b, and the remainder T4a. 35% of cases were stage II disease, 43% stage III, and 22% stage IV. No difference was noted between T4a and T4b tumours for tumour differentiation, or lymph node positivity. No difference in cancer specific and disease free survival were noted between pT4a and pT4b tumours, however significantly divergent survival curves were found for EMVI positive and negative disease. The median cancer specific survival for T4a vs T4b was 32 months vs 41 months respectively (log rank p=0.569). Median disease free survival for the same cohort was 23 months vs 36 months respectively (log rank p=0.882). Median Cancer specific survival in patients with and without EMVI was 25 vs 60 months respectively (log rank p. Median disease free survival was 15 months for those with EMVI, compared to 64 months in those without (log rank p.
Conclusion Subtyping of T4 tumours by EMVI status may be a better prognostic indicator than division into T4a and T4b.
Competing interests None declared.
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