A study is designed to evaluate the efficacy of a new drug, KM28. The study will compare KM28 plus standard care versus standard care alone with regard to decreasing the incidence of recurrent breast cancer. The Food and Drug Administration (FDA) will approve the new drug if KM28 plus standard care decreases the rate of breast cancer recurrence by at least 40% compared to standard therapy alone. The recurrence rate on standard therapy is found to be 8%. In order for the FDA to approve KM28, what is the maximal incidence of recurrent disease acceptable for women treated with KM28 plus standard therapy?

Question

A study is designed to evaluate the efficacy of a new drug, KM28.  The study will compare KM28 plus standard care versus standard care alone with regard to decreasing the incidence of recurrent breast cancer.  The Food and Drug Administration (FDA) will approve the new drug if KM28 plus standard care decreases the rate of breast cancer recurrence by at least 40% compared to standard therapy alone.  The recurrence rate on standard therapy is found to be 8%.  In order for the FDA to approve KM28, what is the maximal incidence of recurrent disease acceptable for women treated with KM28 plus standard therapy?

Quizplus · Accepted Answer

The new drug, KM28, will be approved if its associated recurrence rate is decreased by at least 40% compared to the recurrence rate on standard therapy alone, which is given as 8%. As 40% of 8% is 0.40 × 8% = 3.2%, the maximum acceptable recurrence rate is 8% − 3.2% = 4.8%. Another quick solution would be to state that the maximum acceptable recurrence rate is 60% of 8%, which is 0.60 × 8% = 4.8%. An alternate solution involves using relative and absolute risk calculations. The 40% (ie, 0.4) mentioned in the prompt refers to relative risk reduction (RRR), defined as the percent reduction in absolute risk (AR) between the treatment group (eg, KM28 + standard therapy) and the control group (eg, standard therapy). The formula for RRR is: In this example, AR_control, which represents the risk of recurrence with standard therapy, is given as 8% or 0.08. The formula can be rearranged to calculate AR_treatment: Plugging in the values for RRR and AR_control gives: RRR may overstate the effectiveness of an intervention. For example, a RRR of 50% occurs whether a drug decreases the incidence of a disease from 2% to 1% or from 50% to 25%. Clearly, the latter is of greater clinical significance. Educational objective: Relative risk reduction = (absolute risk_control − absolute risk_treatment) / absolute risk_control

A Study Is Designed to Evaluate the Efficacy of a New