Background: Several randomized control trials (RCTs) have showed that adding either abiraterone acetate (AA) or docetaxel (D) to androgen-deprivation therapy (ADT) improves survival of metastatic castration-sensitive prostate cancer patients (mCSPC). Yet, the cost-effectiveness of these treatment options has not been fully compared under Hong Kong's setting. This cost-effectiveness analysis (CEA) serves as the first study in Hong Kong to compare the economic value of these two combinations ADT + AA vs. ADT + D.
Methods: A deterministic Markov model is used to project cost-effectiveness of each treatment until death. Survival curves for progression/death were extracted and digitized from the five RCTs (CHAARTED, LATITUDE, two STAMPEDE (2016/2017), and GETUG-AFU15). Clinically significant adverse events (AEs) were modeled; utility values were obtained from the literature. Primary outcomes were the quality-adjusted life years (QALYs) and incremental cost-effectiveness ratio (ICER). We used the societal perspective from Hong Kong and considered three times of local gross domestic product per capita (GDPpc) as the willingness-to-pay (WTP) threshold (i.e., US$138,649). We estimated the break-even cost of AA in case ADT + AA is not a cost-effective strategy under this WTP threshold. While considering the standard AA dosage (1000 mg) as the main analysis, we also examined the potential impact of the low-dose AA (250 mg) strategy.
Results: Integrating simulations with probabilistic sensitivity analysis, ADT + D returns 0.79 (median; 95% credible interval 0.56-0.97) QALY with an ICER of US$14,397/QALY ($7824-22,632) compared to ADT-alone. A head-to-head comparison indicates that ADT + AA further gains 0.79 (0.45-1.17) QALY but with an ICER of $361,439/QALY ($260,615-599,683) when compared to ADT + D. Considering three times of GDPpc as WTP threshold, ADT + D is more cost-effective in all simulations; while ADT + AA is more cost-effective than ADT + D only if the cost of AA is reduced by at least 63%. The low-dose AA (250 mg) strategy is potentially cost-effective when it generates equivalent efficacy as the standard dosage (1000 mg).
Conclusions: ADT + D is therefore shown to be a more cost-effective strategy than ADT + AA in metastatic castration-sensitive prostate cancer patients in developed economies. Addition of AA substantially improved QALY compared to D but at a significant cost.