Treatment Modalities for Primary Basal Cell Carcinomas

CLINICAL QUESTION: What is the preferred treatment for a primary basal cell carcinoma?

BACKGROUND: Basal cell carcinoma (BCC) is the most common nonmelanoma skin cancer in the world, with incidences varying between 146 and 317 per 100,000 population in the United States. This slow-growing, locally invasive tumor is most often successfully treated with outpatient office procedures. The authors performed a systematic literature review comparing the effectiveness of 7 treatment modalities for primary BCC: Mohs micrographic surgery (MMS), surgical excision (SE), cryosurgery (CS), curettage and electrodesiccation (CE), radiotherapy (RT), immunotherapy (IM) with interferon or fluorouracil, and photodynamic therapy (PDT) (the latter 2 are investigational).

POPULATION STUDIED: The authors selected and summarized 18 studies, with a total number of 9930 patients treated for primary BCC: 2660 treated with MMS in 3 studies, 1303 with SE in 3 studies, 798 with CS in 4 studies, 4212 with CE in 6 studies, 862 with RT in 1 study, 95 with IM in 1 study, and 0 with PDT (no studies met the inclusion criteria). The broad source base and variety of languages of the primary studies suggests a wide range of patient characteristics such as age, geography, race, and skin type. However, details are not offered. Also undefined are the clinical settings. Exclusion criteria included nonprimary BCC (recurrences), retrospective studies, studies with less than 5 years of follow-up or less than 50 patients, and studies of treatment modality combinations.

STUDY DESIGN AND VALIDITY: This was an extensive review of the literature from 1970 through 1997, including original research published in English, French, German, Dutch, Italian, and Spanish. The search included MEDLINE, EMBASE and CANCERLIT; dermatology yearbooks from 1978 through 1996; and other textbooks, reviews, editorials, existing guidelines, and study references. Of the 298 prospective studies identified, 51% were found using MEDLINE, and 18 met the inclusion criteria. The authors do not describe how they evaluated the quality of studies.

OUTCOMES MEASURED: The studies were quite heterogeneous. The primary outcome measure was the 5-year recurrence rates of treated primary BCCs. The recurrence rates were tabulated from studies as either the raw recurrence rate (absolute number of patients with recurrence divided by number of patients with primary BCC at the start of the study), the strict recurrence rate (absolute number of patients with recurrence divided by number of patients with primary BCC observed for at least 5 years), or the life-table cumulative 5-year recurrence rate. Other outcomes such as cost, cosmetic results, and patient satisfaction were not measured.

RESULTS: The heterogeneity of study designs, reporting methods, and outcomes measured precluded extensive comparisons between studies. Raw recurrence rates may be artificially low, strict recurrence rates too high, and cumulative 5-year recurrence rates were not consistently available. In studies reporting life-table cumulative 5-year rates, the rate of recurrence ranged from 0% to 18.8% across the 5 most common therapies, but lacked otherwise conclusive trends. On the basis of these data, evidence-based guidelines for the treatment of primary BCC cannot yet be developed. Within some treatment modalities, variations in recurrence rates were consistent with risk factors previously identified in the literature. Higher rates of recurrence were associated with certain histologic BCC subtypes (micronodular, adenoid and morphea), location in the H-zone of the face or on ear or eyelid, and size larger than 2 centimeters. The authors conclude that surgical excision remains the treatment of choice for primary BCC, and that MMS is recommended for larger BCCs in the H-zone of the face and those with more aggressive growth patterns; however, both of these conclusions are not definitively supported by their data.