Aims: Lack of inclusion of underserved groups in clinical trials and clinical research is well documented. This can lead to health data poverty and suboptimal care for poorly represented groups. Much less is known about representative diversity in supportive care trials. This study aimed to assess inclusion and bias in psychological intervention trials in people with cancer.
Methods: Primary studies from recent systematic reviews of psychological interventions targeting common issues (anxiety and fatigue) were assessed for barriers to inclusion and biases. Data on pre-specified items were extracted using a standardised data extraction form in Covidence to ensure data quality and rigour. Power to detect small (d=0.4) and medium-sized (d=0.5) effects, assuming a two-tailed alpha=0.05 t-test, was assessed.
Results: 104 primary studies were included (anxiety, n=71; fatigue, n=33). Most studies had poor ethnocultural representation and were under-powered considering published guidance for sample size calculations. Approximately two-thirds (n=65, 63%) explicitly excluded people who could not speak the dominant language of the study country. Only one made reference to the use of bilingual researchers and translated study materials. Females were clearly over-represented, with 49% (n=51) of studies recruiting breast cancer patients only. Studies rarely required participants to be experiencing the issues targeted by interventions (anxiety, 10%; fatigue, 45%). Only 53 (51%) studies were powered to detect a medium-sized effect and 36 (35%) powered to detect a small-sized effect.
Conclusions: Health services looking to implement psychological interventions for common issues experienced by cancer patients must be aware that evidence arises from samples that do not reflect the diversity of the population they serve. Frameworks and guidelines exist to promote inclusion and participation in health research, and these must be used to ensure meaningful diversity in study samples so all people with cancer have the opportunity to benefit from healthcare innovations.