Why carry out this study?

The occurrence of severe local adverse skin reactions during topical treatment can affect patient adherence to therapy and therefore compromise efficacy.

By their mode of action, topical treatments for actinic keratosis (AK) may cause local skin reactions. The severity of local skin reactions may be due to the extent of the field of cancerisation.

What was learned from the study?

Treatment of AK with topical 5-fluorouracil 4% once daily showed less severe local skin reactions compared with a 5% formulation twice daily.

A cut-off value of 10 pre-treatment lesions seems to be meaningful for anticipating possibly severe skin reactions during topical 5-fluorouracil treatment.