A personalized and systematically designed adherence intervention improves photoprotection in adults with xeroderma pigmentosum (XP): results of the XPAND randomized controlled trial

Background Poor adherence to photoprotection in xeroderma pigmentosum (XP) increases morbidity and shortens lifespan due to skin cancers. Objectives To test a highly personalized intervention (XPAND) to reduce the dose of ultraviolet radiation (UVR) reaching the face in adults with XP, designed using known psychosocial determinants of poor photoprotection. Methods A two-arm parallel group randomized controlled trial, including patients with suboptimal photoprotection to receive XPAND or a delayed-intervention control arm that received XPAND the following year. XPAND comprises seven 1 : 1 sessions targeting photoprotection barriers (e.g. misconceptions about UVR) supported by personalized text messages, activity sheets and educational materials incorporating behaviour change techniques. The primary outcome, mean daily UVR dose to face across 21 days in June-July 2018, was calculated by combining UVR exposure at the wrist with a face photoprotection activity diary. Secondary outcomes were UVR dose to face across 21 days in August 2018, time spent outside, photoprotective measures used outside, mood, automaticity and confidence to photoprotect. Financial costs and quality-adjusted life years (QALYs) were calculated. Results Sixteen patients were randomized; 13 provided sufficient data for primary outcome analysis. The XPAND group (n = 8) had lower mean daily UVR dose to face [0.03 standard error of difference (SED) (SD 0.02)] compared with controls (n = 7) [0.43 SED (SD 0.17)] (adjusted difference = -0.25, P < 0.001, Hedge's g = 2.21) at the June 2018 assessment. No significant between-group differences were observed in time spent outside, photoprotection outside, mood or confidence. The delayed-intervention control showed improvements in UVR dose to face (adjusted difference = -0.05; Hedge's g = -0.1), time outside (adjusted difference = -69.9; Hedge's g = -0.28) and photoprotection (adjusted difference = -0.23, Hedge's g = 0.45) after receiving XPAND (June 2019 assessment). XPAND was associated with lower treatment costs [-2642; pound 95% confidence interval (CI) -8715 pound to 3873] pound and fewer QALYs (-0.0141; 95% CI -0.0369 to 0.0028). Conclusions XPAND was associated with a lower UVR dose to face in patients with XP and was cost-effective.