Stage

TNM: see above.

Dukes' A tumour limited to the wall, nodes negative

B tumour beyond the muscularis propria, nodes negative

C1 nodes positive, apical node negative

C2 apical node positive.

Astler Coller modification: A tumour confined to the mucosa

B1 tumour limited by muscularis propria, node negative B2 tumour through muscularis propria, node negative C1 tumour limited by muscularis propria, node positive C2 tumour through muscularis propria, node positive.

Jass classification: more often used in a research setting, it assesses the extent of local tumour spread, lymph node involvement, quality of the invasive margin and density of lymphocytic infiltrate at that margin to derive a score which allocates the lesion to one of four prognostic groups, giving more refined discrimination than the usual Dukes' staging. For routine practice Dukes' and pTNM are recommended.

Resection

RO tumour completely excised locally

R1 microscopic involvement of margin by tumour (to within 1 mm) R2 macroscopic tumour left behind or gross involvement of margin

RO = clear proximal, distal and radial margins irrespective of serosal involvement.

Prognosis

Adverse prognosis

— tumour perforation (pT4) and obstruction.

— poor differentiation.

— splenic flexure lesion.

— young and old age due to delay in presentation and greater numbers of mucinous and signet ring tumours.

Prognosis relates mainly to tumour stage (particularly peritoneal and nodal spread), differentiation and adequacy of local excision with overall 5-year survival 35-40%. National screening programmes for 50-70-year-olds with 2-yearly faecal occult bloods, and if positive, follow-up colonoscopy are geared to detecting a higher percentage of Dukes' A cancers and increasing 5-year survival.

Stage Dukes' 5-year survival A 95%

Differentiation Well/moderate Poor

Local excision CRM positive CRM negative

25% with 85% risk of local recurrence 75% with 10% risk of local recurrence

Not infrequently there is poor correlation between surgical and histo-logical assessment of margin clearance. A positive resection margin (usually the CRM) has strong (x12 risk) prognostic significance for local recurrence and death (x3 risk). It is one of the most important causes of morbidity in rectal cancer. Low rectal cancers also have higher recurrence rates than mid- or upper rectal tumours. For every 100 patients with colorectal cancer it is estimated that 50 will be cured, 10 will die from pelvic recurrence, five from lymphatic spread and 35 from haematogenous spread. Sites of spread are regional nodes, liver (75%), lung (15%), bone and brain (5% each). Patients with bone marrow micrometastases are reported by some to have shorter disease-free survival, but the clinical significance of the immunohistochemical and molecular detection of minimal residual disease in lymph nodes and marrow samples which are tumour negative on routine examination awaits results from large international trials.

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