Concorde Syndrome in the Treatment of People with Cancer: Validation of a Measurement Instrument.

Background: Clinical decision-making in oncology is influenced not only by clinical guidelines but also by psychological, emotional, and social factors, especially in end-of-life care. One such influence is Concorde syndrome, known as the sunk cost fallacy, where past investments lead physicians to continue treatment even when it is no longer medically justified. Although discussed in behavioral science, this phenomenon has not been systematically measured in oncology practice. Therefore, this study aimed to develop and validate a psychometric instrument to assess the psychosocial factors contributing to potentially irrational continuation of treatment among medical oncologists managing patients with no remaining therapeutic options.

Method: This cross-sectional psychometric study comprised both scale development and validation phases. Item generation was informed by literature review and expert consultation, followed by a two-round Delphi panel for content validation and pilot testing. The final 20-item CONCORD Scale underwent exploratory and confirmatory factor analyses, as well as assessments of internal consistency, test-retest reliability, and construct validity.

Results: Exploratory factor analysis (EFA) was conducted with a sample of 116 medical oncologists, and confirmatory factor analysis with 337 participants in Turkey. EFA revealed a four-factor structure: (1) Emotionally Driven Decision-Making, (2) Impact of Prior Clinical Experience, (3) Professional Pressure and Anxiety, and (4) Patient-Centered Decision Conflict. These factors accounted for 74.2% of the total variance, with item loadings ranging from 0.594 to 0.754. Confirmatory factor analysis confirmed good model fit (CFI = 0.937, RMSEA = 0.052, GFI = 0.834). Cronbach's alpha coefficients ranged from 0.834 to 0.948 across subscales and reached 0.969 for the overall scale. Significant inter-subscale and total score correlations further supported structural validity.

Conclusion: The CONCORD (Continuation Over Necessity: Cognitive and Overriding Reasons in Decision-making) Scale is the first validated instrument to quantify emotional, experiential, professional, and interpersonal factors that may lead oncologists to continue treatment beyond clinical necessity in end-of-life care. It offers a novel tool for both research and educational use in ethically sensitive clinical contexts.