Estimating the real cost of adjuvant (A) trastuxumab (T) in patients(pts) with HER-2+ (H+) early stage breast cancer (ESBC)

Abstract

6081 Background: Pts with H+ metastatic (M) ESBC have a high risk of relapse. T has been reported to reduce the risk of relapse for pts with H+ESBC by approximately 50% when combined with A chemotherapy (CT). We attempted to study the real cost of AT in the context of current use of T in MBC (MT), and of the predicted reduction in the risk of relapse. Methods: We conducted a retrospective analysis of the mean per pt cost of AT and MT, and standard ACT in St. Vincent’s Hospital. The costs/pt for AT and MT were €34k, and €47k respectively, and for the listed agents in standard A: docetaxel(D)-8.8k, paclitaxel(P)-7.4 k, filgrastim(G)-9.3 k. Based on published/presented data (BCIRG 001), we assumed a 35% risk for relapse at five years for pts with H+BC receiving conventional A, and a 50% risk reduction (RR) for AT, giving an absolute benefit of 17.5%. We then devised an equation to calculate the Crp for AT: Crp=[a-M(NRA/104)]/[NRA/104] where a = cost per pt for treatment (Tx) with AT, M = cost per pt for Tx with T in MBC, N = % of pts relapsing after standard A, RA = % reduction in the risk of relapse after Tx with AT (over standard A). Results: The corresponding real T costs/100 pts for the following reductions in relapse rate would be:25%-€3.4m 50%-€2.6m-, 80%-€2.1m, 100%-€1.8m. The Crp for AT with a 50% reduction in relapse rate is €147k. With a 100% reduction in the RR we estimate the Crp to be €50k. We studied D (D-BCIRG 001), P (P-CALGB 9344) and G (G-CALGB 9741 dose-dense), and noted the following published absolute relapse reductions for these tx: D-7%, P-5% and G-4%. The following costs per relapse prevented were calculated: P-148 k; G-231k; D-126k. Conclusions: Using the equation, the real cost per relapse prevented of AT can be calculated, and comparisons made with the cost-effectiveness of other accepted A. Assuming no re-treatment with MT, AT appears to be a relatively cost-efficient means of reducing relapses. Reports of the efficacy of short AT regimens suggest the possibility of even greater cost-effectiveness. This equation could possibly be used to calculate the cost effectiveness of other novel A molecular therapies. [Table: see text]