Mesorectal lymph node dissection: is it beneficial?

Locoregional recurrences and distant metastases are the determinants of the long-term prognosis following curative resection of rectal carcinoma. While distant metastases cannot be affected by the surgical treatment of the primary tumor, avoidance of local recurrence by the surgeon is of special significance as the predominant prognostic factor. Analysis of the long-term results achieved by various surgeons led to the concept of mesorectal excision – the removal of the rectum together with all additional tissue invested by the adjacent visceral fascia, that is, fatty tissue, lymph nodes, and lymphatic vessels, by sharp dissection of the appropriate anatomical plane. In our own patient material the 5-year survival rate following R0 resection was 85% for all stages, provided no local recurrence developed. This contrasts with a figure of only 23% in those who did develop local recurrence. The local recurrence rate decreased from 39.4%, with a 50% 5-year survival rate in 1974, to 9.8% and a 71% survival rate in 1991, although the rate of distant metastases remained constant. Among the patients treated between 1988 and 1994 the local recurrence rate was determined by depth of infiltration (1987 UICC classification: pT1 0%, pT2 10%, pT3 14%, pT4 28%), extent of lymph node infiltration (pN0 6%, pN1 15%, pN2 26%, pN3 25%), grading (G1 9%, G2 12%, G3 21%), and location within the rectum (upper third 13%, middle third 8%, lower third 17%), with combinations of unfavorable initial factors leading to higher local recurrence rates. The elevated local recurrence rates seen in the 1970s, in particular in the case of tumors of the lower third, were traced retrospectively to incomplete mesorectal excision, the implementation of which reduced the local recurrence rate initially to less than 10%, and then to the current 4.1%. From the oncological point of view, mesorectal excision must be considered to confer considerable benefit. In the case of carcinomas of the upper third of the rectum, mesorectal resection carried out to just 5 cm below the lower tumor edge is sufficient, however, without coning, while deeper carcinomas mandate total mesorectal excision.