Addition of Apalutamide to ADT Improves Survival in Castration-Resistant Prostate Cancer

In previously reported data from the randomized, placebo-controlled, phase III SPARTAN study, researchers found that the addition of apalutamide to ongoing androgen deprivation therapy (ADT) improved metastasis-free survival (MFS) by more than two years in patients with high-risk non-metastatic castration-resistant prostate cancer and prostate-specific antigen doubling time of 10 months or less. The addition of apalutamide also reduced the risk of symptomatic progression by 55% and increased second progression-free survival (PFS2; time from randomization to disease progression on first subsequent anticancer treatment or death).

In an update from the study that was presented at the 2019 ASCO Annual Meeting, researchers assessed this treatment in older patients and observed an MFS benefit for all age groups.

 Patients were randomized 2:1 to receive continuous apalutamide 240 mg once daily or placebo. Baseline characteristics among age groups were similar, although Eastern Cooperative Oncology Group performance status score increased with age.

The addition of apalutamide significantly impacted MFS (primary outcome; see TABLE).

In the oldest patient cohort (≥75 years), MFS risk was reduced by 59% with apalutamide compared with placebo. MFS risk was reduced by 86% and 76% among patients <65 years and 65 to 74 years, respectively. Risk of PFS2 was reduced across all age subgroups in those receiving apalutamide.

There was a similar increase in incidence of treatment-related adverse events (AEs) with age in both arms, with a higher incidence in the apalutamide group. The researchers noted that the safety profile of apalutamide was similar across age subgroups.

 Reference

Graff JN, Smith MR, Saad F, et al. Age-related efficacy and safety of apalutamide (APA) plus ongoing androgen deprivation therapy (ADT) in subgroups of patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC): Post hoc analysis of SPARTAN. Abstract #5024. Presented at the 2019 ASCO Annual Meeting, Chicago, IL, June 1, 2019.

 

Mean HR P Value Median MFS Symptomatic Progression P Value
<65 years old
Placebo (n=43) 1.00a  

<0.0001

7.3 (95% CI, 3.8-22.0) 1.00a  

0.0133

Apalutamide (n=106) 0.14 (95% CI, 0.07-0.27) NR 0.29 (95% CI, 0.11-0.77)
65 to 74 years
Placebo (n=169) 1.00a  

<0.0001

14.6 (95% CI, 11.0-18.3) 1.00a  

0.0005

Apalutamide (n=307) 0.24 (95% CI, 0.18-0.34) NR 0.42 (95% CI, 0.26-0.68)
≥75 years
Placebo (n=189) 1.00a  

<0.0001

18.5 (95% CI, 16.2-22.8) 1.00a  

0.072

Apalutamide (n=393) 0.41 (95% CI, 0.31-0.56) 40.5 (NE) 0.59 (95% CI, 0.33-1.05)
aReference

HR = hazard ratio; MFS = metastasis-free survival; CI = confidence interval; NR = not reached; NE = not estimable