Development and Psychometric Validation of a Knowledge Assessment Tool on Radiotherapy Resistance Among Oncologists in Iraq.

Radiotherapy resistance (RTR) is a significant barrier in oncology, affecting treatment outcomes and clinical decision-making. Despite its importance, no standardized tool exists to measure oncologists' knowledge of RTR. This study aimed to develop and validate a comprehensive questionnaire to assess oncologists' knowledge of RTR. A 29-item questionnaire was developed following a multi-phase process. An initial pool of 45 items was refined through content and face validity assessments by a panel of 5 experts, leading to item revisions and deletions. Data were collected from 400 oncologists in Iraq. Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were conducted to establish construct validity, while Cronbach's alpha, Composite Reliability (CR), and Item Response Theory (IRT) analysis were used to assess internal consistency and item performance. EFA confirmed the eight-domain structure of the questionnaire, with factor loadings exceeding 0.70 for all items. CFA demonstrated good model fit, with indices of CFI = 0.92, TLI = 0.91, and RMSEA = 0.06. Internal consistency was high, with a Cronbach's alpha of 0.93 and a CR of 0.94 for the overall questionnaire. IRT analysis revealed that all items had acceptable difficulty, discrimination, and guessing parameters, indicating that the items effectively differentiate oncologists with varying levels of knowledge. The final 29-item questionnaire covered key RTR domains, including Conventional and Combined Therapies, Radioresistance, and Sensitivity and Resistance. The validated 29-item knowledge questionnaire demonstrated strong psychometric properties, making it a reliable tool for assessing oncologists' knowledge of RTR. This tool can support oncology education, training, and research. Future studies should focus on cross-cultural validation, test-retest reliability, and examining how RTR knowledge influences clinical decision-making. This tool is especially relevant for improving oncology training and clinical decision-making in Iraq, where systemic barriers such as limited equipment, training gaps, and uneven access to radiosensitizers challenge cancer care.