New international study shows access to patient-reported outcome data improves the consistency of the evaluation of cancer treatment adverse events

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.

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.

“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.

“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 European Organisation for Research and Treatment of Cancer (EORTC) is a non-governmental, non-profit organisation, which unites clinical cancer research experts, throughout Europe, to define better treatments for cancer patients to prolong survival and improve quality of life. Spanning from translational to large, prospective, multi-centre, phase III clinical trials that evaluate new therapies and treatment strategies as well as patient quality of life, its activities are coordinated from EORTC Headquarters, a unique international clinical research infrastructure, based in Brussels, Belgium.

The EORTC Quality of Life Group (QLG) strives to improve health-related quality of life (HRQoL) of cancer patients, through dedicated research and the use of HRQoL measures within cancer clinical trials and clinical practice. HRQoL constitutes an important aspect of cancer research and care: it gives a voice to patients, putting their experience at the forefront. The QLG is part of the European Organisation for Research and Treatment of Cancer (EORTC).

Caroline Hance (EORTC QLG Communications)
caroline.hance@eortc.org