Objective: Circumferential resection margin involvement (CRMI) after resection of rectal cancer is regarded as a risk factor for local recurrence. We have been able to identify only nine peer-reviewed English-language publications which focus primarily on this association, and they report widely differing rates of local recurrence. The aims of this study were to review possible reasons for this variability and to assess the evidence for the micrometrically measured threshold defining CRMI.
Method: Methodological and statistical evaluation of relevant literature.
Results: Several factors which could account for this variability are discussed including the nature of the patient series, surgical technique, curative vs palliative resections, pathology technique, the definition of CRMI, adjuvant therapy, tumour stage, definition and ascertainment of local recurrence, length of follow-up and method of analysis. The objective evidence for the conventional definition of CRMI as tumour 1 mm or less from a circumferential margin is considered along with the evidence supporting a recent proposal that the margin be extended to 2 mm or less. The evidence is numerically weak in both cases and we believe that neither definition should be set in concrete at this stage.
Conclusion: Pending further research, we recommend that routine pathology reports should record frank tumour transection, if present, or otherwise report the histological width of the margin between the tumour and the nearest circumferential line of resection in millimetres. The definition of CRMI should be simply histological evidence of tumour in a line of resection, that is, a margin of 0 mm. The definition of CRMI as a margin of <or=1 mm should not be adopted as a basis for assessing the quality of surgery.