Anal carcinomas are an uncommon group of heterogeneous lesions that have represented a therapeutic enigma for many years. The mere rarity of these cancers alone has proven to be a major impediment to the formulation of a standardized approach to treatment planning.
Much of our current knowledge about the natural history and the biology of these tumors derives from small, single-institution, retrospective reviews of questionable scientific merit that extended over long periods and lacked appropriate control groups or utilized historical controls. These data have been further criticized due to the anatomic definition of the components of the anal canal and anal margin and the nonstandardization of the staging systems used until the American Joint Committee on Cancer (AJCC) and International Union Against Cancer (UICC) systems became widely accepted after 1987.[1,2]
In addition, treatment modalities for anal cancer have varied with individual institutional experience and bias. Compounding this even further, there has been variation even within individual institutions in terms of the chemotherapy regimens utilized, methods of delivering radiation therapy (interstitial implant vs external beam), and whether a single modality or combined approach was employed. Important therapeutic end points, such as disease-free survival and site of first failure, have also been glaringly omitted from many of these published series.
Collectively, the nonuniformity of the existing data prevents them from being subjected to meaningful statistical evaluation. The article by Drs. Mendenhall, Copeland, and associates of their institutional experience and their review of the literature, published in the December issue of ONCOLOGY (10:1843-1854, 1996), addresses some of these important issues and stands as a commendable attempt to formulate a structured approach to the treatment of this rare entity.
It is clear that the management of this disease represents another example of the necessity for a multimodality approach to solid tumors. This approach mandates consultation among surgeons, medical oncologists, and radiation oncologists to formulate the therapeutic strategy that ensures the best outcome, measured not only by disease-free and overall survival but also, importantly, by functional preservation.
The primary goals of treatment have evolved to include not only local control and improved survival but also preservation of normal anal function. Although an abdominoperineal resection was the preferred approach in the past, with time, it has become well accepted that perianal lesions are not as invasive and do not metastasize to regional lymph nodes as frequently as their anal canal counterparts, and therefore, do not necessitate this radical treatment.
Many series have subsequently reported on the feasibility of local excision for early-stage, small tumors that do not demonstrate invasion of the surrounding, deeper tissue. In a previous institutional review of 16 patients treated for perianal squamous cell carcinomas by Schraut et al at The University of Chicago, the concept of local excision for treatment of the tumors was supported by a 67% absolute 10-year survival. This paralleled the experience of Papillon et al, who, in a 1992 review of epidermoid carcinoma of the anal margin, clearly demonstrated the benefit of local excision in controlling the disease and concomitantly preserving sphincter function. Local recurrences were generally controlled by repeat excision or by the more radical abdominoperineal resection. Abdominoperineal resection was used successfully in 3 of 10 patients in the series of Cutuli et al and in 2 of 8 patients in the Cleveland Clinic series.
A number of conclusions can be drawn from a review of the literature, such as that provided by Mendenhall et al. These conclusions agree with our own experience. We concur with Mendenhall et al that early T1 and T2 lesions may be treated with either local excision with clear margins or radiotherapy. One can accept the relatively high local recurrence rate with these approaches since the recurrences tend to be amenable to further excision, radiotherapy, or abdominoperineal resection for cure.
Stage T2 and more advanced lesions should be considered for prophylactic groin irradiation due to the significant likelihood of regional nodal disease. In their series of 57 patients, Papillon et al found a high incidence of inguinal lymph node recurrence in those individuals with T2-T3, N0 tumors. This was their rationale for elective bilateral inguinal irradiation at the time of treatment of the primary lesion. Other investigators, such as Cutuli's group, found no inguinal recurrences in patients with N0 tumors who received prophylactic groin irradiation. In all of these series, there was minimal treatment-associated morbidity. Taking these data into consideration, it seems reasonable that, in patients with T2 or more advanced lesions, groin irradiation be instituted at the time of treatment of the primary cancer. It is unclear at present whether this therapy achieves statistically improved disease-free or long-term survival.
More advanced T3 and T4 cancers are best treated with the combination of cytotoxic chemotherapy and radiation therapy, with abdominoperineal resection reserved for patients with poor sphincter function (manifested by fecal incontinence) and for those fortunate individuals who experience a significant clinical response with downstaging of their tumors to allow for consideration of potentially curative surgery. There does not appear to be any role for prophylactic regional lymph node dissection.
Role of Lymph Node Dissection
The role of either hypogastric lymph node/extended pelvic lymph node dissection or radical groin dissection has been a topic of debate for many years. According to our institutional experience and the experience of other surgeons, perianal squamous cell carcinoma rarely metastasizes to pelvic lymph nodes, and thus, does not warrant routine dissection. Inguinal node involvement--a well accepted, poor prognostic factor--occurs with relatively high frequency in patients with more advanced tumors. However, since radical groin dissection is attended by considerable morbidity and severe disability, it is difficult to justify a prophylactic dissection on theoretical grounds alone. Inguinal lmph node dissection is still used for local control of nodal disease.
Importance of Follow-up
Lastly, one important, seemingly obvious point in the management of cancers of the anal margin is the need for careful, close interval follow-up by examination and proctoscopy for early detection of local or nodal recurrences. Given the sometimes indolent pattern of these tumors, such follow-up should be continued for at least 10 years.