To explore perceptions regarding the approved and actual prescribed doses of protein kinase inhibitors (PKIs) in clinical practice in the European Union among medicine regulators and healthcare professionals (HCPs).

A qualitative descriptive study was conducted using semistructured interviews, continuing until thematic saturation was reached. Thematic analysis was undertaken using a combined deductive-inductive approach. Deductive main analytical themes were derived from the theoretical framework of questioning-based policy design, namely problem sensing, problem categorisation and problem decomposition. Subthemes were generated inductively and could coherently be situated within these main analytical themes.

Interviews were held online or in person at a location convenient for the interviewee, depending on the participant’s preference.

Seven medicine regulators involved in the regulation of cancer medicines—including PKIs—and 10 HCPs prescribing PKIs in clinical practice, from various countries within Europe, were included.

Regulators highlighted insufficient attention to optimal dose finding, yielding approved doses often based on outdated maximum tolerated dose concepts, leading to uncertainties in efficacy and safety. HCPs reported using alternative dosing strategies in clinical practice to improve tolerability and quality of life (QoL) but noted a lack of robust evidence to guide such adjustments and faced legal constraints to deviate from the approved dose. Participants emphasised the need for improved pre-approval and post-approval dose optimisation to improve safety, enhance QoL and bridge gaps between trial data and real-world patient diversity.

Collaborative efforts involving multistakeholders including HCPs, regulators, pharmaceutical companies, insurers, governments and patient representatives are essential to advance dose optimisation and improve patient-centric outcomes, with further research needed to understand these stakeholders’ perspectives.