The degree of extramural spread of T3 rectal cancer: an appeal to the American Joint Committee on Cancer

The T3 category of the TNM classification includes over 60% of all rectal tumours and encompasses the greatest variance in cancer-specific end-points than any other T category. The most recent edition of the cancer staging handbook of the American Joint Committee on Cancer (AJCC) dated 2010 does not divide T3 tumours into subgroups which reflect cancer-specific outcome more sensitively. The original aim of the present study was to review the literature to assess the influence of the degree of extramural extent of T3 rectal cancer on local recurrence and survival. An article written by the authors was accepted for publication but was withdrawn immediately after they became aware of the publication of the 4th edition of the TNM Supplement by the Union for International Cancer Control dated 2012, which was not accessible by the search system used. This article dealt with the subdivision of the T3 category although this was not included in the most up-to-date AJCC guidelines and was stated to be ‘entirely optional’. Medline, PubMed and Cochrane Library searches were performed to identify all studies that investigated the degree of extramural spread and its relationship to survival and local recurrence. Twenty-two studies were identified of which 12 assessed the degree of histopathological extramural spread measured in millimetres. In 18 of the 22 studies the degree of extramural spread was a statistically significant prognostic factor for survival and local recurrence. Analysis of the studies indicated that the subdivision of category T3 rectal cancer into two subgroups of extramural spread ≤ 5 mm or more than 5 mm resulted in markedly different survival and local recurrence rates. The data were insufficient to allow validation of any greater subdivision. Measurement of the extent of extramural spread by MRI before any treatment agreed with the histopathological measurement in the surgical specimen to within 1 mm. The extent of extramural spread in T3 rectal cancer measured in millimetres is a powerful prognostic factor. A subdivision of T3 into T3a and T3b of less than or equal to or more than 5 mm appears to give the greatest discrimination of local recurrence and survival. Preoperative T3 subdivision by MRI has the same sensitivity as histopathological examination of the resected specimen. Given the clinical need for the pretreatment classification of the T3 category for oncological management planning, the evidence strongly indicates that the subdivision of the T3 category by MRI should be formally considered as part of the TNM staging system for rectal cancer.