Efficacy of curettage before excision in clearing surgical margins of nonmelanoma skin cancer

Objective: To determine whether curettage before excision of basal cell car cinoma (BCC) and squamous cell carcinoma (SCC) improves margin clearance ra tes. Design: A retrospective, nonrandomized, case-control series of nonmelanoma skin cancers treated with preexcisional curettage followed by simple excisi on was identified using a computerized search of the database of a dermatop athology service. A validation cohort was established by manually identifyi ng nonmelanoma skin cancers treated with wide excision on a given day. Setting: All analyzed specimens were derived from the Dermatopathology Serv ice at the University of California, San Francisco, a university-based labo ratory that provides interpretation of skin biopsy specimens received direc tly from community (90%) and academic (10%) practices. Patients: Our retrospective cohort consisted of all nonrecurrent nonmelanom a skin cancers diagnosed by biopsy and treated by simple excision between A pril 1, 1997, and April 30, 1999. There were 1983 BCCs and 849 SCCs include d in our study. The validation cohort included skin cancers diagnosed by bi opsy treated with simple excision on the 16th day of each month during the same period. Intervention: Preexcisional curettage. Main Outcome Measure: We compared the frequency of tumor margin involvement of curetted vs noncuretted lesions. Margin involvement was considered surg ical failure. Results: Forty-two percent of BCCs and 34% of SCCs were curetted before exc ision. In BCC, risks for surgical failure included head and neck lesions (P <.001), lesions treated by physicians performing fewer than 51 procedures ( P<.001), and invasive subtypes (P<.01). Factors associated with surgical fa ilure in SCC included in situ disease (P=.01) and an older (77 vs 74 years) patient population (P=.05). In univariate analysis, curettage before excis ion decreased the surgical failure rate for BCC by 24% (P=.03) but did not decrease the rate for SCC (P=.8). In multivariate analysis, curettage of BC C reduced surgical failure rates by 26% when the physician performed 50 ski n cancer excisions or less during the study (odds ratio, 0.74; 95% confiden ce interval, 0.57-0.95; P=.02). Conclusion: Preoperative curettage decreases the frequency of positive marg ins in the management of BCC but not of SCC.