Inconsistent reporting of adolescent and young adult (AYA) status in non-interventional cancer research: a critical barrier to evidence usability.

Inconsistent reporting of age at cancer diagnosis limits the utility of non-interventional studies focused on adolescents and young adults (AYAs), defined by the National Cancer Institute as individuals diagnosed between ages 15 and 39. Standardised reporting is essential to synthesise evidence and develop targeted interventions to address this population's unique needs. While initiatives have emphasised reporting age at study enrolment in reporting results, there is a lack of guidance on specifying age at diagnosis-an essential detail for accurately identifying AYA status.To estimate the scope of this problem, we reviewed 734 non-interventional cancer studies published between 2018 and 2022 and found that 33% did not report age at diagnosis sufficiently to determine AYA inclusion, with no improvement over time. We recommend that future reporting guidelines explicitly require age-at-diagnosis metrics, including mean, median, range and count of participants diagnosed between ages 15 and 39, to improve data comparability of non-interventional AYA cancer research and accelerate targeted interventions. We further recommend that studies with mixed-age samples report outcomes stratified by AYA status wherever sample size permits.