SCIN (curettage then imiquimod against excision for nodular basal cell carcinoma)

The creams are licensed for the thin superficial form of basal cell carcinoma. SCIN asked whether they could be stretched to the commoner nodular form by scraping the visible tumour away first, on the reasoning that curettage removes the bulk and the cream deals with what is left. Two Dutch dermatology departments randomised 145 patients with a primary nodular basal cell carcinoma of 4 to 20 mm between January 2016 and November 2017, 73 to superficial curettage followed by imiquimod and 72 to surgical excision. Follow-up finished in September 2022.

Fifteen treatment failures occurred in the curettage and imiquimod group, five of them between one and five years, against one in the surgery group. The probability of remaining free from treatment failure at five years was 77.8 per cent after curettage and imiquimod (95 per cent confidence interval 65.7 to 86.0) against 98.2 per cent after excision (88.0 to 99.8). The relative risk of treatment failure was 15.93 (2.10 to 120.64), and its confidence interval does not exclude the pre-specified non-inferiority margin of 5.22, so non-inferiority could not be concluded. Twenty patients died of causes unrelated to the skin cancer during follow-up; accounting for that as a competing risk gave a subhazard ratio of 16.16 (2.18 to 119.72).

The authors' own reading is worth keeping, because it is the honest version of a negative trial: most failures happened in the first year, and a person who is still clear a year after curettage and imiquimod has a 77.8 per cent chance of staying clear at five. That is a real option for someone who cannot or will not have an operation on the face. It is not equivalence.