Selection of endpoints in breast cancer clinical trials: a qualitative study of key trial stakeholders

Clinical trial endpoints are fundamental for evaluating the safety and efficacy of cancer therapies, yet it is not well understood how they are selected or the role of stakeholder groups in deciding endpoints. This study aimed to explore how clinical trial endpoints are selected in breast cancer trials of anti-cancer drugs through semi structured interviews with purposively selected stakeholders involved in breast cancer clinical trials (clinicians, consumers, pharmaceutical company representatives, and members of drug regulatory agencies). Participants were asked to describe the process of selecting trial endpoints. Interviews were transcribed verbatim and analysed using inductive thematic analysis supported by NVivo software. Saturation of the main themes was reached and the final sample included 25 participants from 14 countries (9 clinicians, 7 consumers, 5 members of regulatory agencies, 4 pharmaceutical company representatives). Pharmaceutical companies were almost always identified as the main decision maker. While most consumers and pharmaceutical company representatives felt clinicians and consumers influenced trial design, some clinicians and regulators reported consumers and clinicians had little influence. Factors identified as important considerations in determining trial endpoints included the main goal of the trial, established standardised endpoints, resources, and the investigational agent studied. All pharmaceutical advisors reported that meeting the requirements for regulatory approval was the major factor considered. Clinical trial endpoint selection is largely decided by the pharmaceutical industry, driven by requirements for regulatory approval. Given the limited influence from clinicians and consumers, guidance by regulatory agencies will be important for future inclusion of novel endpoints in clinical trials.