What facets of physical function are most important to adults diagnosed with cancer?

Successful patient-focused drug development involves selecting and measuring outcomes in clinical trials that are important to patients. The U.S. Food & Drug Administration's definition of clinical benefit includes how patients feel, function, or survive. Patients are considered the experts in describing how they feel and function. In cancer trials, patient-reported measures of physical function provide insight into how patients function at baseline, benefit from the interventions being studied, and the impact of treatment side effects. We conducted a qualitative study with adults diagnosed with cancer to describe facets of physical function from their perspective and to identify which facets are most important to this patient population.

Using concept elicitation and cognitive interviewing techniques, we conducted semi-structured interviews with 72 adults ≥ 22 years of age with cancer who received treatment with an anticancer drug or biologic within six months of the interview. We selected participants using purposive sampling with the aim to elicit diverse experiences regarding how they may interpret and respond to questions related to physical function. Participants were presented with patient-reported outcome (PRO) items representative of PRO measures used in cancer and general populations.

Five facets of how physical function relates to activities were defined from the patient perspective: ability, difficulty, limitation, satisfaction, and completion. More than half of the participants indicated that ability was the most important facet of physical function. The next most important were satisfaction (18.3%), limitation (14.1%), difficulty (5.6%), and completion (2.8%).

This study demonstrates that we must be more specific about the facets of physical function that we set out to assess when we use PRO measures to describe the patient experience. These results have implications for the specificity of physical function facets when measured in cancer clinical trials.