Patient and Caregiver Treatment Preferences in Type 2 and Non-ambulatory Type 3 Spinal Muscular Atrophy: A Discrete Choice Experiment Survey in Five European Countries

Abstract

Spinal muscular atrophy (SMA) is a rare neuromuscular disease that affects motor neurons, resulting in progressive skeletal muscle weakness and atrophy. The aim of this study was to examine treatment preferences of patients and caregivers of patients with Type 2 and non-ambulatory Type 3 SMA in the Netherlands, Belgium, Finland, Ireland and Portugal. A discrete choice experiment (DCE) survey was developed to elicit the preferences of adult patients and caregivers regarding different treatment aspects of SMA. This survey built on the design of a similar study undertaken in the UK. The DCE described choice questions in terms of attributes and levels combined using a D-efficient design. The attributes described improvements or worsening in motor and breathing function. The mode of treatment administration (intrathecal injection, single intravenous infusion or regular oral therapy) was described. Treatment risks and side effects related to currently available treatments including risk of liver injury, fatigue, headache, nausea, diarrhoea and rash were described. Lastly, an attribute described whether a treatment had evidence of treatment effectiveness in different SMA types. Participants were recruited via patient advocacy associations to complete an online survey. A clustered conditional logit model was used to estimate treatment preferences. Participants (n = 65) were 4.8 times and 8.1 times more likely to choose a treatment with stable or improved (vs worse) motor function, respectively. Similarly, participants were 4.3 times and 5.8 times more likely to choose stable or improved (vs worse) breathing function, respectively. Treatments with a risk of liver injury, fatigue, headache and nausea were 1.6 times less likely to be chosen than treatments with a risk of diarrhoea and rash. Treatments with demonstrated effectiveness in Type 1 SMA only were 2.3 times less likely to be chosen than those with demonstrated effectiveness in Types 1–3 SMA. Treatments administered via intrathecal injections were also 1.8 times less likely to be chosen than daily oral treatments. Study results show the importance of improvement as well as stabilisation of motor and breathing function to patients and caregivers, and a preference for oral treatments, treatments with demonstrated effectiveness in Types 2–3 SMA, and avoidance of liver injury risk.