(Neo)adjuvant approvals for solid tumors by the US Food and Drug Administration 2010-2023

BACKGROUND: (Neo)adjuvant systemic treatments aim to improve overall survival (OS)_by reducing recurrence risk; however, there can be challenges, such as reliance on surrogate endpoints, censoring, loss to follow-up, and impact on quality of life (QOL). We examine the design, reporting, and outcomes of Food and Drug Administration (FDA)-approved drugs for solid tumors. METHODS: We searched FDA (neo)adjuvant approvals for solid tumors 2010-2023 with time to event-endpoints. Trial characteristics, endpoints, and censoring were evaluated descriptively. Statistical designs and sample size calculations were assessed for reproducibility and transparency. RESULTS: Twenty-four studies supporting 25 approvals met inclusion criteria. Common tumor types included melanoma (7/24, 29%), breast (6/24, 25%) and non-small cell lung cancer (6/24, 25%). Among 21 trials reporting OS, 52% (11/21) showed benefit at any time, but only 36% (4/11) reported OS benefits at the time of approval and/or primary publication. In 21 trials (88%) the expected number of events could be reproduced, in 11 trials (46%) sample size calculations could be attempted (though calculations often differed), and only 14 (58%) stated expected absolute numerical outcomes. Censoring rules were applied inconsistently, only 36% defined rules adequately. QOL outcomes were reported in 79%, with 31% reported clinically meaningful declines in one or more domains. CONCLUSIONS: (Neo)adjuvant trials often lack transparency in sample size justifications and censoring rules. Approximately half demonstrated an OS improvement at any time, and one third showed a decline in QOL. Greater standardization in trial designs and reporting is needed to ensure trials align with patient and healthcare priorities.