Real-World Effectiveness and Treatment Persistence of Darolutamide, Apalutamide, and Enzalutamide in Non-Metastatic Castration-Resistant Prostate Cancer: A Multicenter Study - Beyond the Abstract
Three androgen receptor signaling inhibitors (ARSIs)—darolutamide, apalutamide, and enzalutamide—are each guideline-recommended for non-metastatic castration-resistant prostate cancer (nmCRPC), yet no head-to-head randomized trial exists to directly compare them.
Network meta-analyses suggest broadly equivalent oncological efficacy, but these are derived from clinical trial populations that systematically exclude older, comorbid patients typical of real-world practice. Furthermore, most real-world comparative data come from Western cohorts, leaving a gap in evidence for Asian populations—who may have distinct pharmacogenomic characteristics and adverse event profiles. We previously compared apalutamide and enzalutamide in a Japanese multicenter cohort and identified marked differences in tolerability. With sufficient darolutamide experience now accumulated across our institution network, a three-drug comparison became feasible.
What We Found
In 343 Japanese patients with nmCRPC treated across 16 institutions, the key finding was a dissociation between oncological outcomes and treatment persistence. Oncologically, all three agents performed comparably. Although multivariable Cox regression identified a statistically significant PSA progression-free survival advantage for darolutamide versus enzalutamide (HR 0.55, P=.038), this finding was attenuated and lost significance after propensity score matching (HR 0.62, P=.119). The apparent advantage in the Cox model most likely reflects residual confounding by indication: enzalutamide was introduced earlier in Japan and was disproportionately prescribed to higher-burden patients. PSA response rates were virtually identical across all three agents, reinforcing the interpretation of equivalent antitumor activity.
The clinically meaningful differentiator was treatment persistence. Median time to treatment discontinuation was 27.0 months for darolutamide and 25.0 months for enzalutamide, compared with only 11.0 months for apalutamide (P=.019). Among patients who discontinued apalutamide, adverse events were the primary reason in 82.5%—overwhelmingly driven by skin rash, which occurred in 46.9% of apalutamide-treated patients. This rash incidence substantially exceeds the approximately 24% reported in the SPARTAN trial and is consistent with prior Japanese and East Asian reports. In contrast, darolutamide demonstrated the lowest overall adverse event rate (29.3%) and the lowest rate of AE-driven discontinuation (19.6%).
What This Means Clinically
In a disease where sustained drug exposure is the mechanism of benefit—continuous androgen receptor blockade to delay metastasis—treatment persistence is not a secondary consideration. It is a direct determinant of clinical outcome. A patient who discontinues apalutamide at a median of 11 months due to rash loses the oncological benefit that the drug would otherwise confer, regardless of its in-trial efficacy. This study reframes the ARSI selection question from "which drug is most efficacious?" to "which drug will the patient actually remain on?"
The high prevalence of apalutamide-associated rash in East Asian patients is likely multifactorial. Differences in body weight affect drug exposure, and pharmacokinetic data suggest higher plasma concentrations in lower-weight populations at standard dosing. Host immune susceptibility and heterogeneity in institutional rash management protocols may also contribute. Systematic investigation of dose modification strategies or prophylactic dermatologic intervention specifically in Asian patients represents an important unmet need.
Darolutamide's favorable tolerability profile has mechanistic underpinning. Its substantially lower blood-brain barrier penetration compared to enzalutamide and apalutamide likely explains the lower incidence of CNS-related adverse events such as fatigue and dizziness—particularly relevant in the typically elderly nmCRPC population where cognitive and physical function preservation is clinically meaningful. Its distinct drug-drug interaction profile further supports its use in patients with comorbidities requiring polypharmacy.
Limitations and Future Directions
This study is retrospective and subject to the inherent limitations of real-world observational research, including residual confounding and informative censoring. The darolutamide cohort had substantially shorter follow-up than the other groups, leaving long-term endpoints such as MFS and OS immature. The staging was based on conventional imaging; PSMA PET-CT was not routinely available during the study period in Japan, and some patients classified as non-metastatic may have harbored occult micrometastases. These limitations are inherent to the real-world setting and do not negate the central finding regarding treatment persistence, but they underscore the need for prospective comparative data.
Future studies should examine whether systematic rash management protocols—including prophylactic antihistamines or structured dose reduction algorithms—can improve apalutamide persistence in East Asian patients. Additionally, the lower rate of subsequent taxane-based chemotherapy in the darolutamide group warrants prospective investigation; whether superior initial tolerability translates into preservation of chemotherapy candidacy at the time of disease progression is a clinically relevant question.
Conclusion
In routine Japanese clinical practice, darolutamide, apalutamide, and enzalutamide appear oncologically equivalent. The principal differentiator is tolerability and treatment persistence. Given the disproportionate burden of apalutamide-associated rash in East Asian patients and the requirement for sustained therapy to achieve meaningful disease control, treatment selection in this population should prioritize long-term tolerability alongside efficacy. These findings support individualized ARSI selection, with darolutamide offering a favorable balance of sustained exposure and tolerability for patients in whom treatment persistence is the priority.
Written by: Shuhei Hara, MD, PhD, Department of Urology, The Jikei University School of Medicine, Tokyo, Japan; Department of Urology, Jikei Katsushika Medical Center, Tokyo, Japan
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