Quality-adjusted time without symptoms or toxicity (Q-TWiST): patient-reported outcome or mathematical model? A systematic review in cancer.

ABSTRACT

OBJECTIVE: Successful cancer treatment is defined as an increase in overall survival and/or progression-free survival. Despite their importance, these metrics omit patient quality of life. Quality-adjusted time without symptoms or toxicity (Q-TWiST) was developed to adjust survival gained, accounting for quality of life. The purpose of this systematic review was to assess the methods reported in cancer literature to determine Q-TWiST values and how these are currently translated to the clinic. METHODS: The Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines were used to conduct a systematic review of studies indexed on MEDLINE and Web of Science through April 2013. Cancer studies that measured Q-TWiST either as a primary outcome or retrospectively and determined utility coefficients from a patient population were identified, and their methods reviewed to determine how the utility coefficient was calculated. Additionally, other relevant factors such as definitions of health states and significant findings were collected and summarized. RESULTS: Out of 284 studies, 11 were identified that calculated patient-defined utility coefficients. Several methods to determine utility coefficients were reported, and multiple definitions of health state toxicity were applied. Of these studies, seven reported significant differences (p < 0.05) in quality-adjusted survival. No studies, however, directly discussed the clinical relevance of their findings. CONCLUSIONS: Currently, Q-TWiST is utilized as a mathematical theory rather than a clinical tool. Standardization of terminology plus reliability and validity testing of determining both utility coefficients and time frame definitions must be performed before Q-TWiST can become clinically useful to physicians and patients alike for making treatment decisions.