Actinic keratosis-related signs predictive of squamous cell carcinoma in renal transplant recipients: a nested case-control study.

Background: Squamous cell carcinoma (SCC) and intraepidermal carcinoma (IEC) commonly arise in actinically damaged skin.
Objectives: To identify clinical features of actinic change that correlate with an increased risk of SCC or IEC in the short-to-medium term as guidance for prioritizing field treatment.
Methods: In a nested case-control study, cases were renal transplant recipients who developed an incident SCC or IEC within 18 months following baseline examination and photography. Controls without SCC or IEC were matched to cases on age, sex and duration of immunosuppression. Predefined skin sites on the head, neck and upper limbs were examined using baseline photographs to assess objectively the following features of actinic damage: presence of actinic keratosis (AK) patch (defined as AK > 1 cm ² ), number of AK patches, number of AKs and area affected by AK. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using McNemar's test to identify differences in SCC/IEC risk combined and SCC risk alone between case and control skin sites.
Results: Thirty-nine cases were matched to 39 controls. Significant associations with the presence of an AK patch, number of AK patches, number of AKs and area affected by AKs were identified. The presence of an AK patch conferred an 18-fold increased risk of SCC (OR 18·00, 95% CI 2·84-750) and more than a sixfold increased risk of SCC/IEC combined (OR 6·60, 95% CI 2·56-21·66).
Conclusions: AK patches are predictive of SCC/IEC development within 18 months. This can be used to guide site selection for field treatment in patients with widespread actinic damage.
(© 2016 British Association of Dermatologists.)