Background The treatment tradeoff method (TTM) has been developed specifically for decision-making at the level of the individual patient. By altering the probability of an outcome, a preference score is obtained of one treatment relative to another. As the task is tailored to the clinical decision problem at hand, the method may be more relevant to the patient than are methods for utility assessment, such as the time tradeoff technique (TTO). Nevertheless, the TTM still needs thorough evaluation.

Purpose The aim of the present study was to evaluate the TTM in rectal cancer patients subjected to either sphincter-saving surgery (low anterior resection, LAR) or sphincter non-saving surgery, resulting in a permanent stoma (abdominoperineal resection, APR), by relating the treatment tradeoffs to TTO utilities of the treatment outcome states (permanent stoma, fecal incontinence).

Methods 102 randomly selected disease-free rectal cancer patients from a large randomized trial were interviewed: 50 had undergone LAR, 52 had undergone APR. Instruments included two TTMs (permanent stoma vs daily or monthly fecal incontinence, respectively) and three TTOs (permanent stoma and daily or monthly fecal incontinence vs good health).

Results APR patients on average were willing to take a risk of daily and monthly fecal incontinence of 23% and 28%, respectively, before accepting a permanent stoma, whereas LAR patients on average were willing to take 77% and 92% risk, respectively (both p's<.001). The utility of a permanent stoma differed significantly between the two patient groups (0.88 vs 0.58, p<.001), but not the utilities of daily fecal incontinence (0.54 vs 0.53, p=.96) and monthly fecal incontinence (0.63 vs 0.73, p=.09). Linear regression analysis showed that the utilities of permanent stoma and fecal incontinence were both predictive of the treatment tradeoffs (R2=0.33, p<.001 and R2=0.38, p<.001 for the models with daily and monthly incontinence, respectively), with the utility of permanent stoma being the most predictive variable.

Conclusion The outcomes of the regression analysis indicate that patients indeed tradeoff during the TTM, although the preference for sphincter-saving surgery seems to be influenced more by the valuation of a permanent stoma than by the risk of incontinence. Besides clarifying patients' values for treatment outcome states, the TTM may detect other motives for preferring one treatment over the other.