The sum of all fears: conceptual challenges with measuring fear of cancer recurrence.

Fear of cancer recurrence (FCR) is increasingly recognised as a major concern for people with cancer once active treatment is completed. Several instruments have been designed to assess FCR; however, no gold standard has emerged. Many instruments conceptualise FCR as a multidimensional construct. However, this potentially conflates FCR as an outcome with its antecedents and consequences. This is problematic when an aggregate of distinct dimensions is calculated, as is commonly recommended. For example, the total score on the Fear of Cancer Recurrence Inventory is an aggregate of items from seven sub-scales: triggers, severity, psychological distress, coping strategies, functioning impairments, insight and reassurance. Similarly, the total score on the Fear of Progression Questionnaire is an aggregate of affective reaction, partnership/family, work and loss of autonomy. Arguably, the severity and affective reaction domains represent fear, and the other sub-scales represent related concepts, rather than "dimensions" of FCR. The total score represents a combination of concepts whose meaning is unclear. The same total score could be produced by patients with very different experiences, and patients with the same level of fear could have very different total scores. Therefore, we argue that although the level of FCR may be determined by a complex network of antecedents and modifiers and have variable consequences, FCR itself may be a simple concept, which can be assessed using a smaller number of items. Conceptual clarity in its research infancy should prevent FCR becoming a construct that is vaguely operationalised and interpreted.