Importance Melanoma is one of the most lethal skin cancers: it has become the fifth commonest cancer in the UK and incidence rates are rising rapidly. Population approaches have focused on mass media campaigns to promote earlier presentation and potentially improve melanoma outcomes. Interventions using smartphone applications (‘Apps’), targeted to those at greatest risk, could promote earlier presentation to healthcare for people with new or changing skin lesions.

Objective To study a commercially available Skin Self-Monitoring (SSM) App in people at increased risk of melanoma on help-seeking for changing skin lesions. Design and setting Phase II randomised controlled MelaTools SSM trial, conducted in 12 family practices in Eastern England between 2016 and 2017, with participants followed up 12 months, and analysis conducted in 2018.

Participants Eligible participants were aged 18-75 and at increased risk of melanoma, identified using a real-time melanoma risk assessment tool in family practice waiting rooms.

Intervention Once randomised, both groups received a consultation with standard written advice on sun protection and skin cancer detection. The intervention group also had the SSM App ‘MySkinPal’ loaded into their smartphone, received instructions for use, and monthly self-monitoring reminders.

Main outcome/s and measures The co-primary outcomes were skin consultation rates with family practice physicians and ‘patient intervals’ measured as the time from noticing a skin change to family practice consultation. Follow up questionnaires were sent at 6 and 12 months, and consultation rates were extracted from family practice records. Secondary outcomes included: skin self-examination benefits and barriers, self-efficacy for consulting without delay, perceived melanoma risk, sun protection habits, and potential harms.

Results 238 patients were randomised (119 intervention; 119 control; median age 55 (IQR 43-65), female 55%, white British 95.4%). Overall, 51 people consulted about skin changes during the 12 months of follow up and 157 people responded to at least one follow-up questionnaire. There were no significant differences in skin consultation rates (adjusted risk ratio 1.0 (95% CI 0.6 to 1.7)), or measures of SSM or psychological harm.

Conclusions Recruitment, retention and initial delivery of the intervention were all feasible, and this research provided no evidence of harm from the SSM app. However, we found no evidence of benefit on skin self-examination or healthcare consulting and no reason at this stage to recommend its implementation in this population at increased risk of melanoma.