Background: Studies have shown that utilities for a particular treatment, elicited by means of a hypothetical treatment scenario, may remain stable within the same patients when examined before, during, and after experiencing that treatment (within-group stability). However, other studies have found that utilities for a particular health state may differ between patient groups who are and who are not experiencing the particular health state (between-group differences).
Objective: The authors evaluated this apparent contradiction in the case of adjuvant chemotherapy for breast cancer. A related purpose was to examine whether a chemotherapy scenario adequately reflects the patients' own experiences with chemotherapy.
Method: Forty-three patients with early-stage breast cancer evaluated their actually experienced health state and a chemotherapy scenario before, during, and after undergoing adjuvant chemotherapy (chemotherapy group). A control group of 51 patients for whom chemotherapy was not part of the treatment plan was interviewed at similar points in time. Utilities were elicited by means of a visual analog scale (VAS), a chained time trade-off (TTO), and a chained standard gamble (SG).
Results: The utilities for the chemotherapy scenario remained relatively stable over time in the 2 patient groups. Furthermore, the chemotherapy scenario was evaluated more positively by patients in the chemotherapy group than by control patients (e.g., utilities before chemotherapy: VAS 0.69 vs. 0.50, TTO 0.88 vs. 0.50, SG 0.92 vs. 0.58, all Ps < 0.01). Finally, patients in the chemotherapy group evaluated their actually experienced health states during chemotherapy higher than the chemotherapy scenario that was assessed at the same time (VAS 0.79 vs. 0.69, TTO 0.93 vs. 0.87, SG 0.97 vs. 0.96, all Ps < 0.05).
Conclusions: Both within-group stability and between-group differences were found. A possible explanation for within-group stability may be that the chemotherapy scenario did not fully correspond to the patients' actual experiences with chemotherapy ("noncorresponding description"). Therefore, preferences did not change even when the patients' own clinical health status had changed. The between-group differences may be explained by "anticipated adaptation." Both explanations may work together to explain why utilities remain stable within the same patients but differ between different patient groups.