Calculating cost per event avoided using a composite number needed to treat

Number needed to treat (NNT) and cost per event avoided (CPEA) are measures used to represent the clinical and economic value of chronic treatments and are commonly calculated based on primary endpoints from trials. This approach, although widely used, does not reflect the complete value of a treatment, as it does not consider outcomes beyond the primary endpoints. This research aims to overcome this limitation by developing multiple composite NNTs to derive the CPEA to estimate a total value of semaglutide and dulaglutide in people with established cardiovascular disease.

Two cardiovascular outcomes trials were selected, SELECT (NCT03574597, semaglutide 2.4 mg) and REWIND (NCT01394952, dulaglutide 1.5 mg). NNT was calculated as NNT = 1/ARR where ARR = control event rate - experimental event rate. NNT was estimated for 3-point major adverse cardiovascular events (MACE-3; primary endpoint of the trials), 5-point MACE (MACE-5), and cardiovascular-kidney-metabolic events (CKM). CPEA of MACE-3, MACE-5, and CKM was calculated as NNT*duration of mean follow-up (semaglutide) or duration of median follow-up (dulaglutide)*estimated net price.

The NNT decreased as the number of outcomes in the composite endpoint increased, where NNT_MACE-3, NNT_MACE-5, and NNT_CKM were 67, 49, and 8 for semaglutide, and 72, 64, and 23 for dulaglutide, respectively. Similarly, the CPEA decreased as the number of outcomes in the composite endpoint increased, where the CPEA for MACE-3, MACE-5 and CKM calculations were $1,662,001, $1,232,417, and $190,387 for semaglutide and $1,884,013, $1,670,366, and $607,886 for dulaglutide.

This research illustrates the limitations of using a NNT focused only on the primary endpoint, as it does not capture the total benefit of the treatment. When considering the value of treatments through NNT or CPEA analyses, a composite endpoint capturing broader benefit should be utilized.