Cost-effectiveness of adding enzalutamide vs standard non-steroidal antiandrogen drugs for patients with metastatic hormone-sensitive prostate cancer undergoing standard first-line therapy: a within-trial, secondary end-point analysis of the ENZAMET phase 3, international randomized trial (ANZUP 130

Adding enzalutamide to standard therapy cost substantially more per patient over 60 months than non-steroidal antiandrogen therapy.

• Enzalutamide was associated with an additional AUD$127,262 per patient in healthcare costs over the first 5 years.
• The analysis took an Australian health system perspective, with costs in 2023 Australian dollars.
• Data came from ENZAMET trial records, linked Medicare claims and patient questionnaires.

Enzalutamide gave modest gains in life-years and quality-adjusted life-years over 5 years.

• Gains were 0.24 life-years and 0.15 QALYs in the first 5 years compared with non-steroidal antiandrogen therapy.
• QALYs were estimated by multiplying mean health utility (converted from EQ-5D-5L using a validated algorithm) by life-years accumulated.
• Median follow-up was 68 months, with a data cut-off of January 19, 2022.

The incremental cost-effectiveness ratios were far above the willingness-to-pay threshold.

• The ICER was AUD$543,880 per life-year gained.
• The ICER was AUD$835,580 per QALY gained.
• The willingness-to-pay threshold used was AUD$50,000 per QALY gained.

Results were sensitive to the price of enzalutamide, and a much lower price would meet the cost-effectiveness threshold.

• A purchase price of AUD$6.73 per tablet yielded an ICER meeting the AUD$50,000 per QALY threshold.
• Deterministic and probabilistic sensitivity analyses varied the unit price of study drugs, hospital per diem rates, Medicare benefits paid and health utility values.
• Missing data were assessed and imputation applied where relevant.

Hospitalizations and musculoskeletal medicine use were slightly higher in the enzalutamide group, suggesting falls and fractures.

• The authors interpret higher use of musculoskeletal medicines as indicating falls and fractures.
• The authors conclude that long-term bone health management in survivors is an important clinical consideration.

The study concludes that enzalutamide improves quality-adjusted survival in mHSPC but is unlikely to be cost-effective at current pricing.

• This is a within-trial analysis using prospectively collected observed data from the ENZAMET open-label phase 3 RCT.
• Funding came from Astellas Pharma and the Australian National Health and Medical Research Council.