Histologic subtype of treatment failures after noninvasive t
There have been concerns that recurrences after noninvasive therapy for basal cell carcinoma (BCC) transform into a “more aggressive” histologic subtype.

Researchers 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.

-- The proportion of more aggressive early failures was significantly lower after imiquimod (26.3%) compared with methylaminolevulinate–photodynamic therapy (54.8%) and 5-fluorouracil (66.7%).

Conclusively, more aggressive treatment failure recurrences after noninvasive therapy for superficial BCC occur most often within the first 3 months posttreatment, probably indicating underdiagnosis of more aggressive components in the primary tumor rather than transformation.

Source: https://www.jaad.org/article/S0190-9622(18)33100-1/pdf