Is relative risk reduction a useful measure for patients or families who must choose a method of treatment?

1 report the results of a study that examined the impact of using four different risk/benefit measures when communicating survival benefits to individuals charged with deciding whether to recommend chemotherapy for their mothers. The four measures defined by the authors were relative risk reduction, absolute risk reduction, absolute survival benefit, and number needed to treat. Two hundred four individuals (51 per measure) were randomly assigned to make a decision after being given survival information using one of the measures, then were allowed to make a new decision after receiving the value of all four measures. The principal findings were that individuals who received only the relative risk reduction information were significantly more likely to endorse chemotherapy, were the least confident in their decision, and were highly likely to change their decision when presented with the other three measures of risk/benefit. In fact, the percentage of individuals who recommended chemotherapy when presented with only relative risk reduction for a small tumor was 51.0%, but this figure decreased to 39.2% when the individuals were presented with all the information. For a larger tumor, 70.6% of the individuals recommended chemotherapy when presented with relative risk information, but the figure decreased to 45.1% when the individuals were provided with complete data. Decisions based on any of the three other methods of communicating risk did not change nearly as frequently as the decision based on relative risk reduction when all four measures were subsequently presented. The authors concluded that absolute survival benefit was the best measure. A potential weakness of the study (noted by the authors) was that, for practical reasons, the individuals used in this study were medical students, who almost certainly would understand these measures better than many of the individuals who have to make these difficult decisions in real life. However, this fact only heightens the point that even bright, medically oriented people were uncomfortable using relative risk, a common measure in medical research, to make a treatment decision for a relative. Three examples presented below help illustrate the difference between the four measures and provide some insight into why the relative risk reduction might be a poor measure to use alone when making an individual treatment decision. Table 1 lists the survival information used in the first scenario presented to individuals in the Chao et al 1 study. The assumption is that historical data show a particular type of breast cancer …