Histologic subtype of treatment failures after noninvasive therapy for superficial basal cell carcinoma: An observational study

Abstract

There have been concerns that recurrences after noninvasive therapy for basal cell carcinoma (BCC) transform into a "more aggressive" histologic subtype. We sought to evaluate the proportion of patients with a nonsuperficial treatment failure after noninvasive therapy for superficial BCC. An observational study was performed using data from a single blind, noninferiority, randomized controlled trial (March 2008-August 2010) with 5-year follow-up in patients with primary superficial BCC treated with methylaminolevulinate-photodynamic therapy, 5-fluorouracil, or imiquimod. Data were used from 166 adults with a histologically confirmed treatment failure. A nonsuperficial subtype was found in 64 of 166 treatment failures (38.6%). Proportions with a more aggressive subtype than the primary tumor were 51.3% (38/74) for early and 28.3% (26/92) for later treatment failures (P=.003). The proportion of more aggressive early failures was significantly lower after imiquimod (26.3%) compared with methylaminolevulinate-photodynamic therapy (54.8%, P=.086) and 5-fluorouracil (66.7%, P=.011). There was limited information on the exact time of occurrence of treatment failures. More aggressive treatment failure recurrences after noninvasive therapy for superficial BCC occur most often within the first 3months posttreatment, probably indicating underdiagnosis of more aggressive components in the primary tumor rather than transformation.