Understanding Patients’ Ability to Function in Order to Inform Clinical Benefit in Oncology Studies

Demonstration of clinical benefit in oncology typically focuses on the impact of treatment on survival and tumour progression. However, as survival benefit data are difficult to obtain in oncology drug development programmes, additional endpoints are needed to complement the evidence of treatment effect on the tumour. To date, little is known of the changes patients experience in day-to-day function due to cancer and/or treatment. We set out to understand the concept of ‘function’ in order to inform its assessment as a patient-relevant endpoint for clinical benefit. Twenty semi-structured interviews were conducted to explore how cancer patients describe their daily functioning. Patient interviews and the literature were then used to develop a conceptual framework of function. Patients interviewed were diverse: eight cancer types (all solid tumours, 65% metastatic, 50% with active disease), ECOG status 0–1 (55%) and 2–3 (45%), and 35% having previously received taxanes. The term ‘function’ was not easily understood by patients and 35% did not provide a definition. When describing function, 60 unique concepts were discussed. Four categories of function emerged (mobility, cognition, activities, roles), and later a conceptual framework was developed. Impairments in function were often described as limitations in mobility and/or cognitive abilities. Patients also described 20 different concepts of ‘adaptation’ to overcome cancer or treatment-related impairment and resume their day-to-day function, including change in frequency/intensity, precaution, use of external aids or proactive behaviour changes. ‘Function’ from patients’ perspective is a complex concept; further research is needed to understand the assessment of mobility, cognition, activities and roles as individual concepts for measuring function. In addition, selecting the most appropriate dimension of measurement (e.g., frequency, ability to perform, difficulties completing a task) for each concept is paramount to reliable and meaningful capture of cancer- and/or treatment-related functional impairment.