A large multinational clinical trial has found that giving healthcare providers access to European Organisation for Research and Treatment of Cancer (EORTC) patient-reported outcome (PRO) data significantly improves the consistency of how treatment-related side effects are assessed in patients with cancer. The findings highlight the importance of integrating the patient's voice into routine clinical evaluations and cancer research.
The study by Lisa Wintner et al. 1 , published last week in The Lancet Oncology , evaluated the reliability of the Common Terminology Criteria for Adverse Events (CTCAE), the global standard used by clinicians to grade side effects in oncology trials. While the CTCAE system is widely used to evaluate the severity of adverse events, previous research has shown considerable variation in grading between clinicians.
About the study
Conducted across 11 hospitals in ten countries, this randomised controlled trial enrolled more than 1,000 adult patients with any cancer diagnosis receiving chemotherapy, immunotherapy, or radiotherapy. Providers in the intervention group were able to view patients’ self-reported symptoms as measured by the EORTC QLQ-C30 and selected symptoms from the EORTC Item Library while completing CTCAE assessments; the control group had no access to the patient-reported symptoms.
The results were clear: inter-rater reliability (i.e., how consistently different raters assess the same event) among clinicians was significantly higher when PRO data were available, particularly for psychological and cognitive symptoms such as memory impairment, irritability, concentration difficulties, depression and anxiety. Overall, consistency improved for 13 of the 17 symptomatic adverse events assessed.
Implications for cancer research
“This study demonstrates clear evidence that patient-reported outcomes provide value in the evaluation of the side effects of cancer treatment,” said Bernhard Holzner, Principal Investigator and senior author of the study. Lisa Wintner, lead author and Study Coordinator, added: “When clinicians have direct access to what patients are experiencing in real time, their assessment of side effects becomes more consistent and reliable, ultimately making it more meaningful for patient care and research.”
Importantly, the study represents the first multinational, randomised controlled trial to demonstrate that integrating PRO data directly into clinician assessments can measurably improve the reliability of adverse event reporting. The findings address long-standing concerns that traditional toxicity reporting may underestimate or miss symptomatic adverse events altogether.
Improving cancer care through better measurement
“These results reinforce the need for a hybrid approach that combines clinical expertise with the patient perspective,” added Madeline Pe, Head of the EORTC Quality of Life Department. She explained: “By embedding PRO data into routine evaluations, we can achieve a more accurate and patient-centred understanding of treatment-related side effects.”
The researchers conclude that routine integration of PRO data into CTCAE assessments could strengthen the quality of cancer trials, improve symptom detection, and better reflect the real-world impact of cancer therapies on patients’ quality of life.
These clinical implications are further underlined in an accompanying commentary in The Lancet Oncology by Ethan Basch and Amylou Dueck, internationally recognised for their work integrating patient reported outcomes into oncology trials and routine care. 2
1 Lisa M Wintner, Monika Sztankay, Hikmat Abdel-Razeq, et al. Inter-rater reliability of CTCAE assessments with or without EORTC patient-reported outcome data in a mixed cancer population: a multinational, open-label, randomised controlled trial. The Lancet Oncology, 2026, ISSN 1470-2045, https://doi.org/10.1016/S1470-2045(25)00679-5
2 Ethan Basch, Amylou Dueck, Sharing patient-reported outcomes with clinical investigators in real time. The Lancet Oncology, Volume 0, Issue 0, https://doi.org/10.1016/S1470-2045(26)00009-4
The Lancet Oncology
Randomized controlled/clinical trial
People
Inter-rater reliability of CTCAE assessments with or without EORTC patient-reported outcome data in a mixed cancer population: a multinational, open-label, randomised controlled trial
19-Jan-2026
LMW's work as study coordinator was funded by the EORTC Quality of Life Group grant awarded to BH. YK received honoraria from Eisai, Daiichi Sankyo, Eli Lilly Japan, Chugai Pharmaceutical, AstraZeneca, and Pfizer Japan. NS' institution received research funding from Daiichi Sankyo, AstraZeneca, and MSD. NS received lecture honoraria from Kyowa Kirin, MSD, Daiichi Sankyo, Chugai Pharmaceutical, Pfizer Japan, Eisai, Taiho Pharmaceutical, Eli Lilly Japan, Nippon Kayaku, Merck Biopharma, and Bristol Myers Squibb and received honoraria for advisory board participation from Kyowa Kirin, Daiichi Sankyo, and Chugai Pharmaceutical. ATa and her institution received grants or contracts from the Russian Science Foundation; ATa received payments from Astra Zeneca, R farm, and AMGEN and received support for attending meetings and/or travel from ESMO. BH was the principal investigator and received a grant from the EORTC Quality of Life Group to fund the study conduct, managed by BH's institution. All other authors declare no competing interests.