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Squamous Cell Carcinoma of the Anal Margin

Squamous Cell Carcinoma of the Anal Margin

This paper consists of a review of the literature on carcinoma of the anal margin, as well as the authors' institutional experience with this uncommon malignancy. The authors offer recommendations for treatment based on the size of the tumor, which correlates with the T-stage from the TNM or Union Internationale Contre le Cancer (UICC) staging systems. They recommend radiation alone or local excision for T1 lesions, radiation and elective nodal irradiation for T2 lesions, and chemoradiation, including irradiation of the primary tumor and inguinal and pelvic nodes, for T3 and T4 lesions.

The authors' series from the University of Florida at Gainesville (1979-1993) consists of eight patients with T2, N0, M0 disease and two patients with T3, N0, M0 disease who were treated with 50 to 69 Gy of radiation, including elective inguinal irradiation. Treatment was accomplished without "severe" complications or compromise of anal function, and there have been no local, inguinal, or distant recurrences with a minimum follow-up of 2 years. The authors also review the literature, as scanty as it is, on staging and natural history, surgical treatment, radiation therapy, and adjuvant chemotherapy.

Important Points Highlighted

The authors highlight several important points about this cancer. Anal margin cancers are defined as those occurring between the dentate line and the hair-bearing perianal skin. Most clinicians agree that the anal canal extends from the anorectal ring to the anal verge. Many tumors occurring in the anal canal straddle the dentate line. In fact, most tumors occurring in the surgical anal canal are treated much the same as "true" anal cancers. There are two reasons for this: (1) the overwhelming success of chemoradiation therapy in achieving local control of anal squamous cell cancer with preservation of anal function and a reduction in the need for permanent colostomy, and (2) the difficulty of attaining successful healing and adequate function after excision of lesions in the anal canal.

When T1 ( 2 cm or less) or even some T2 (2 to 5 cm) squamous cell cancers lie outside the surgical anal canal, excision alone can be successful because of the low incidence of nodal spread. Although such excisions can be technically demanding in terms of wound closure, functional and oncologic results are excellent. Abdominoperineal resection (APR) usually is not needed to treat these cancers.

I would agree with the authors that in cases of T3 or T4 tumors or tumors encompassing more than 50% of the anal verge or anal canal, chemoradiation, including elective inguinal nodal irradiation, is indicated. In light of the authors' ability to deliver treatment to the primary tumor and inguinal nodes with such low morbidity and overall effectiveness, one cannot argue with their approach of treating T2 or more extensive tumors with radiotherapy.

Although the authors present a series with virtually a 100% rate of optimal outcomes, other series that they cite, as well as more recently published series, demonstrate both treatment failures and morbidity with radiotherapy. For example, in a series of 17 patients treated with radiation, Touboul and others found a 40% cancer-related death rate at 5 years for patients with T2 tumors, and severe anal function complications occurred in 2 patients, albeit at radiation doses of 60 to 70 Gy.[1]

Thus, for those who advise and treat patients with anal margin cancers, two challenges remain: (1) the identification of patients in whom conservative treatment is likely to fail, and (2) the delivery of effective treatment with minimal morbidity and preservation of quality of life. The authors are to be commended for their achievement of these goals in their series of patients with T1-2, N0, M0 anal margin cancer.

References

1. Touboul E, Schlienger M, Buffat L, et al: Epidermoid carcinoma of the anal margin: 17 Cases treated with curative-intent radiation therapy. Radiother Oncol (Ireland) 34(3):195-202, 1995.

 
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