Purpose: To investigate whether ACA is a viable option as decision support tool within oncology, by examining the (a) feasibility and test-retest reliability of ACA, (b) consistency of ACA findings, and (c) concordance of findings between ACA and TTM.
Methods: Randomly selected disease-free rectal cancer patients are interviewed who participated in a multicenter trial assessing the benefit of adding pre-operative radiotherapy (PRT) to surgery [Kapiteijn et al., NEJM 2001]. Treatment preferences are assessed based on tradeoffs between side effects (fecal incontinence, sexual problems) and local control (and survival, ACA). Half of the respondents are asked to perform the ACA-task twice. Using TTM, minimally-desired benefit (local control) from PRT+surgery is assessed, given pre-defined risks of side effects. Based on ACA-utilities and TTM, and given the costs and benefits of PRT, respondents' true treatment preference are computed.
Results: As of May 25th, 40 respondents have been recruited. All respondents except one completed the ACA-task. Fifteen (39%) performed the ACA-task twice, at 17±4 days interval. The 17/39 respondents who were presented with one or two dominant choices preferred the best option in 22/27 (81%) cases. Respondents' attribute-level utilities were consistent for 92% (local control), 74% (survival), 64% (incontinence), and 51% (sexual problems). Incontinence was most important in determining preference (30%±13), followed by local control (28%±9), survival (23%±10), and sexual problems (19%±9). Over time, mean importance scores were stable (paired t-tests ns) yet individual scores varied greatly (Pearson's r 0.05-0.39). Comparing ACA- and TTM-based preferences, only 17/36 respondents were congruent.
Conclusion: Findings suggest stable results at group-level yet unstable results at individual-level. Treatment preferences clearly diverge depending on assessment method. It is as yet questionable whether ACA is suitable for assessing individual treatment preferences within oncology.