The National Cancer Institute’s Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) is a library of question items that enables patient reporting of adverse events (AEs) in clinical trials. This study contributes content validity evidence of the PRO-CTCAE by incorporating cancer patient input of the relevance and comprehensiveness of the item library.

Cognitive interviews were conducted among patients undergoing chemotherapy or radiation therapy at multiple sites to evaluate comprehension, memory retrieval, judgment, and response mapping related to AE terms (e.g., nausea), attribute terms (regarding frequency, severity, or interference), response options, and recall period. Three interview rounds were conducted with ≥20 patients completing each item per round. Items were modified and retested if ≥3 patients exhibited cognitive difficulties or if experienced by ≤25 % patients.

One hundred and twenty-seven patients participated (35 % ≤high school, 28 % non-white, and 59 % female). Most AE terms (63/80) generated no cognitive difficulties. The remaining 17 were modified without further difficulties by Round 3. Terms were comprehended regardless of education level. Attribute terms and response options required no modifications. Patient adherence to recall period (7 days) was improved when the reference period was incorporated.

This study provides evidence confirming comprehension of the US English language versions of items in the PRO-CTCAE library for measuring symptomatic AEs from the patient perspective within the context of cancer treatment. Several minor changes were made to the items to improve item clarity, comprehension, and ease of response judgment. This study helps to establish the content validity of PRO-CTCAE items for patient reporting of AEs during cancer treatment.