Response shift in the perception of health for utility evaluation. an explorative investigation

Abstract

We previously showed that patients with newly diagnosed colon cancer change the internal standards on which they base their quality of life estimation. In the present investigation, we explored whether this response shift similarly affects the perception of health for utility evaluation in cancer clinical trials. After radical resection of adenocarcinoma of the colon (pT1-4 pN>0 M0 and pT3-4 pN0 M0) and perioperative chemotherapy, patients were randomised to three treatment arms: observation only (A), 5-fluorouracil (5-FU) 450 mg/m(2) plus levamisol (B), or 5-FU 600 mg/m(2) (C). Subjective health was assessed by a linear analogue self-assessment (LASA) scale anchored at 'perfect health-worst health' developed for serial assessment of utility values (Hürny C, van Wegberg B, Bacchi M, et al. Subjective health estimations (SHE) in patients with advanced breast cancer: an adapted utility concept for clinical trials. Br J Cancer 1998, 77, 985-991). Patients estimated their pre-surgery health among various quality of life indicators both before surgery and retrospectively thereafter, and their pre-adjuvant health both at the beginning of randomly assigned chemotherapy or observation and retrospectively approximately 2 months later. Thereafter, current subjective health was assessed. Paired t-tests were used to test the hypotheses of no change. Patients' estimated pre-surgery health was worse after surgery than before (n=127, mean change=-6.7, standard deviation (S.D.)=30, P=0.01), and their estimated pre-adjuvant health was worse under treatment or observation than at the beginning (n=132, mean change=-7.1, S.D.=23.8, P=0.001), in agreement with the quality of life indicators. Chemotherapy had no impact on these changes attributed to a response shift. Conventionally assessed changes between the beginning of adjuvant treatment or observation and 2 months later indicated no change in subjective health. Change scores relative to patients' retrospective estimation revealed an improvement (n=122, mean change=6.6, S.D.=24.8, P=0.004) in this period. Patients with colon cancer substantially reframe their internal standard of health as they do for quality of life. This explorative finding questions the assumption, generally made in decision models, that health estimates for utility evaluation are independent of time. Given that patients may change their standards, comparisons of health estimates across different populations and clinical situations are to be interpreted with caution.