The exact role of combined-modality therapy and TAE of rectal cancer remains to be defined. Certainly the stakes are high, as studies have shown that the recurrence of locally excised rectal cancer is associated with worse long-term survival outcomes.
We commend Drs. Benson, Guillem, and Minsky on their excellent review of the changes in rectal cancer management. We agree with their current assessment of rectal cancer management, but would also like to include a few notes about local excision (LE) of rectal cancer in our commentary on their article.
Local excision of rectal cancer by standard transanal excision (TAE) or transanal endoscopic microsurgery (TEM) has long been a topic of significant contention, even prior to the landmark report of a series on local excisions in 1977 by Morson et al. In this series of 91 patients who had complete local resection, only 3 had local recurrence, and one of these patients was later cured by radical surgery. Since that time, investigators have vigorously pursued the idea of LE of early-stage rectal cancers.
Unfortunately, subsequent published series produced less favorable results, with local recurrence rates of 17% to 18% for T1 tumors and 26% to 37% for T2 tumors.[2,3] In addition, salvage surgery for recurrent cancer after LE is associated with an overall poor 5-year survival of 53%. In contrast to LE, radical surgery yields a 1.4% risk of local recurrence for T1 tumors and a 6.4% risk of local recurrence for T2 tumors. In terms of overall survival (OS), LE predictably produces worse outcomes, with a 10-year OS of 76% for T1 tumors and 72% for T2 tumors. This compares poorly with radical surgery, in which 10-year OS is 90.4% for T1 tumors and 81.9% for T2 tumors.
From a recovery and functional standpoint, TAE is far superior to radical surgery. In terms of survival and local recurrence, however, radical surgery yields better results. Therefore, the search has been under way to find methods of improving the short- and long-term oncologic outcomes of TAE, and improvements have been seen in recent years. One method for improving the oncologic results of TAE may be TEM. In the TEM procedure, specially designed equipment is utilized to perform a discoid excision of rectal cancer in the standard manner. Proponents of this technique emphasize that the TEM equipment allows better visualization, more precise dissection, and the ability to remove tumors higher in the rectum than could be reached with standard instruments. A comparative study between TEM and TAE has shown a similar complication rate between the procedures (15% and 17%, respectively), but TEM was more likely to yield clear margins (90% vs 71%, P = .001). Local recurrence was also less frequent after TEM (5% vs 27%, P = .004). Advocates of TAE would argue that a local recurrence rate of 27% is unusually high for a TAE series.
Combined-modality chemoradiotherapy in association with TAE of rectal cancer can also yield improved oncologic results. In a prospective, multi-institutional trial, a series of T2 rectal cancer patients was treated with LE followed by adjuvant chemoradiotherapy (5400 cGy given in 30 fractions and fluorouracil [5-FU] at 500 mg/m2 IV on days 1 to 3, and days 29 to 31). Local recurrence was seen in only 13.7% (7 of 51 patients) at 4-year follow-up. Distant recurrence occurred in an additional 5.8% (3 of 10 patients). The authors distinguish between a failure-free survival rate of 71% and an OS of 85%.
TEM surgery has also been combined with adjuvant radiotherapy in T2 rectal cancer patients. A small series of 16 patients who had complete removal of their T2 cancers with TEM were offered adjuvant radiotherapy. At a median follow-up of 3 years, all 12 patients treated with LE and radiotherapy remained disease-free, whereas a 50% recurrence rate was observed in the 4 patients who refused adjuvant radiotherapy.
TEM surgery has also been combined with neoadjuvant chemoradiotherapy in T2 and T3 rectal cancers. In a review of 100 consecutive rectal cancer patients (54 uT2N0 and 46 uT3N0), results were surprisingly favorable, with a 5% local recurrence rate at a median 55-month follow-up. Unfortunately, neoadjuvant chemoradiotherapy was not applied in a uniform manner in this patient group. While all patients received 5400 cGy given in 28 fractions, only 25 patients received continuous infusion of 5-FU (at 200 mg/m2 per day), making this a difficult study to review.
The exact role of combined-modality therapy and TAE of rectal cancer remains to be defined. Certainly the stakes are high, as studies have shown that the recurrence of locally excised rectal cancer is associated with worse long-term survival outcomes. Studies in this area remain small, and the results of ongoing randomized controlled clinical trials are eagerly anticipated.
Financial Disclosure:The authors have no significant financial interest or other relationship with the manufacturers of any products or providers of any service mentioned in this article.
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