Aim: Keratinocyte carcinomas (KC) incidence continues to increase and current therapies do not prevent new lesions occurring within an area of field cancerisation (FC). Immune checkpoint inhibitors (ICI) are an unexplored potential systemic field therapy. We aimed to evaluate the effect of ICI therapy on clinical actinic keratoses (AKs) in FC and keratinocyte carcinomas (KC).
Methods: A prospective observational study in participants with FC on their forearms commencing ICI therapy for an unrelated cancer in a Brisbane public oncology department. The clinical AK count before and 3-months, 6-months and 12-months after commencing ICI therapy was assessed. The number of KC excised 12 months before and after starting ICI therapy was compared. Paired t-test with significant threshold p=<0.05 in SPSS Statistics Software was used.
Results: 23 participants recruited over 6-months, 74% males with a mean age of 69 (SD 9.6). 64% prescribed monotherapy anti-PD-1 and 36% combination anti-PD-1 and anti-CTLA-4. All participants experienced a decrease in the number of clinical AKs. The mean count decreased from 47.2 at baseline to 14.3 (p≤0.001) at 12-months. The number of histologically diagnosed KCs decreased from 45 to 17 in the 12 months before and after starting ICI therapy, including a statistically significant decrease of SCCs from a mean of 0.73 to 0.23 (p=0.019).
Conclusions: This pilot study demonstrates that the use of ICIs for any cancer led to a significant reduction in clinical AKs and in SCCs occurrence, reflecting a benefit on FC as well as a potential for immunopreventive strategies in high-risk populations.