Initial Treatment of Nonmelanoma Skin Cancer
Most nonmelanoma skin cancers can be conservatively excised with much narrower margins than are required for cutaneous melanomas. Excision margins of 0.5 to 1 cm are adequate for most nonrecurrent basal cell and squamous cell cancers and yield local recurrence rates under 5%, provided that histologically negative margins are achieved. For most tumors in most anatomic sites, these excision margins can be achieved using standard surgical techniques with local anesthesia and primary closure.
RT is effective for the treatment of squamous cell and basal cell skin cancers, and is associated with a likelihood of cure similar to that of surgery. However, this practice is only considered standard in areas of the body where surgery would be disfiguring or debilitating. In instances in which negative margins cannot be obtained without an unacceptable cosmetic result, adjuvant RT to treat microscopic residual disease appears effective. This practice is also typically extended to Merkel cell skin cancers and sarcomas of the skin. The use of RT to the surgical bed when negative margins have been obtained is more controversial and is not well supported by data.
Topical and intralesional therapy
Topical therapy is a consideration for patients with large areas of skin affected by numerous or recurrent squamous cell or basal skin cancers. Immunocompromised patients and occasional patients with extremes of cumulative lifetime sun exposure are candidates for topical 5-FU or imiquimod(Drug information on imiquimod). These therapies are generally not offered to patients who are otherwise good candidates for surgical resection. 5-FU is an antimetabolite chemotherapy that is effective in eradicating both actinic keratoses and squamous cell skin cancers. Following treatment, patients typically develop significant erythema in treated skin lasting for several weeks, until the treated skin has adequately regenerated its epithelium. Imiquimod stimulates the activity of antigen-presenting cells in the skin when applied topically, which engenders an immune response in treated tumors. Complete regression of treated tumors is typically achieved. However, patients who are offered this therapy are typically at high risk for local recurrence and appearance of new lesions elsewhere, and thus require lifelong surveillance and, potentially, repeated treatment.
Intralesional therapy for unresectable or recurrent basal cell skin cancers has been investigated. The only readily available agent that has been employed for this purpose is interferon-α. Comparative trials have not been conducted with intralesional vs topical therapies.
Management of Recurrent Nonmelanoma Skin Cancer
Local recurrence complicates approximately 5% of cases of nonmelanoma skin cancer; if possible, surgical resection should be performed. In areas of skin where surgery would result in an unacceptable cosmetic result, RT can be offered. The vast majority of recurrent nonmelanoma skin cancers can be cured with re-excision or RT.
Regional lymph node involvement
Among nonmelanoma skin cancers, Merkel cell carcinoma is the most likely to be associated with regional lymph node involvement. The prognosis of patients with lymph node involvement appears to be significantly worse than that of patients with localized disease. Thus, SLNB is justified as a staging procedure in patients with primary Merkel cell carcinoma. Squamous cell skin cancer is less likely to involve regional lymph nodes (5% of all cases), and SLNB is generally reserved for patients with primary tumors that are large, deeply invasive, or poorly differentiated. Lymph nodes should be evaluated with fine-needle aspiration to determine the need for lymph node dissection. Basal cell carcinoma infrequently spreads to regional lymph nodes.
Distant metastases occur infrequently in squamous cell carcinoma (2% of all cases) and generally are limited to patients who are immunocompromised. Fewer than 1 in 1,000 patients with basal cell carcinoma develop metastatic disease, therefore clinical trials have not been conducted in these patients. Combination chemotherapy regimens used to treat squamous cell carcinoma from other sites are typically employed for patients with metastatic squamous cell carcinoma of the skin, although responses appear to be infrequent and are usually short-lived.