To the Editor:
I read with interest the paper by Marr et al,1 stating that patients undergoing abdominoperineal excision (APR) have a higher local recurrence rate than patients undergoing an anterior resection (AR), and I appreciated the accuracy of their analysis of the surgical specimen.
As an oncologic surgeon involved in rectal resections for many years, I wonder why 2 operations so similar, except for a wider margin of transection at the distal level for the APR, yield different oncologic outcomes.
I question whether the results of the authors’ report, coherently with their findings, could have a different explanation. I suspect that difference in local recurrence rate between APR and AR simply reflects the fact we are dealing with different tumors.
Main factors that favor the adoption of an APR instead of an AR are the distal site of the tumor (tumor of middle or low rectum vs. more proximal tumors) and the presence of a bulky mass and/or a narrow (male) pelvis. For these conditions, sometimes discovered during operation, the surgeon may convert a planned AR to an APR, but almost never does the opposite occur.
The rectum is by definition 15 cm long, and it is conceivable that the mean distance from anal verge is different in patients undergoing APR and AR.
It is well known that tumors of the distal rectum have a poorer prognosis than proximal ones,2,3 even because the lymphatic spread to the iliac and obturator nodes (which are almost never removed by the European surgeons) is more common in these distal tumors,4,5 and this could account for a high recurrence rate.
As a matter of fact, some years ago (in the premesorectal excision era), when we reviewed our experience on 350 tumors of the middle to low rectum, we found at the multivariate analysis a higher risk of recurrence (2.6 times) with AR compared with APR.6 We also reviewed the literature comparing the two procedures for cancer of the middle and low rectum (11 authors, 1400 patients): in no study was there an excess of risk of local recurrence for APR, but three papers reported a statistically significant increase of risk for the AR.6
Furthermore, a very recent nationwide revision of the long-term outcome after standardization of rectal surgery (November 1993 to December 1999) did not find any difference in local recurrence rate after the two operations by multivariate analysis on 3174 patients.7
The role of a bulky tumor mass or of a narrow pelvis in determining the occurence of local recurrence is difficult to assess in quantitative terms. However, in this study, the author attempted to carefully measure the volume of resection and reported that total area of surgically removed tissue outside the muscular propria, as well as the linear dimensions of transverse slices of tissue containing tumor, were smaller in the APR specimen than in the AR group.
This means, in my view, that tumors were bigger in AP compared with AR and/or the volume of resection was by force smaller because in these distal tumors, treated by APR, bony structures limited wider margins of transection. In keeping with this observation is the finding of a lower left lateral measurement in males: since the surgeon stays on the left side of the patient, it is easier to displace the rectum to the left (with the left hand) while resecting the right attachments (with the right hand). When the pelvis is narrow (male pelvis, distal tumors) or the tumor is bulky, or both, this finally results in a smaller margin of transection on the left.
In conclusion, I accept the findings of Marr et al,1 but I think they did not demonstrate a different curative potential of the two operations; rather, the worse prognosis of patients undergoing APR versus the AR did not reflect a lower radicality of the surgical procedure but a more unfavorable biology and anatomic location of tumors treated by APR.
Federico Bozzetti, MD
Hospital of Prato
Prato, Italy
dottfb@tin.it
REFERENCES
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