Apalutamide versus placebo in patients with nonmetastatic castration-resistant prostate cancer: final survival results from SPARTAN, a phase III trial

SPARTAN has evaluated Apalutamide ( Erleada ) versus placebo in patients with nonmetastatic castration-resistant prostate cancer ( nmCRPC ) and a prostate-specific antigen ( PSA ) doubling time of less than or equal to 10 months receiving androgen deprivation therapy ( ADT ).

At primary endpoint analysis of metastasis-free survival ( MFS ), Apalutamide has significantly improved median MFS by 2 years, as well as time to metastasis, progression-free survival ( PFS ), and time to symptomatic progression vs placebo ( Smith, et al. NEJM 2018 ); overall survival ( OS ) results were immature.

SPARTAN was unblinded upon meeting the primary end point; patients still on placebo were allowed to cross over to Apalutamide.

Researchers have reported final survival results.

1207 nmCRPC patients were randomized 2:1 to Apalutamide ( 240 mg QD ) or placebo plus ongoing ADT.
At progression, patients could receive open-label sponsor-provided Abiraterone acetate + Prednisone.

After the primary efficacy end point ( MFS ) was met, 76 placebo patients ( 19% ) crossed over to Apalutamide.

With follow-up of 52.0 months, 428 ( of 427 required ) OS events had occurred. Median treatment duration was: Apalutamide, 32.9 months; placebo, 11.5 months.

Median overall survival was significantly longer with Apalutamide + ADT vs placebo + ADT ( 73.9 vs 59.9 months ), ( hazard ratio [ HR ], 0.784 ).

Apalutamide significantly lengthened time to cytotoxic chemotherapy ( TTCx ) ( HR, 0.629 ).

Discontinuation rates ( Apalutamide vs placebo ) due to progressive disease were 42.7% vs 73.9%, and due to adverse events 15.2% vs 8.4%.

Safety was consistent with previous reports; grade 3/4 treatment-emergent ( TE ) adverse effects of special interest were rash 5.2%, fractures 4.9%, falls 2.7%, ischemic heart disease 2.6%, hypothyroidism 0%, and seizures 0%.
1 TEAE leading to death ( myocardial infarction ) was considered potentially Apalutamide-related.

In conclusions, in patients with nmCRPC, Apalutamide + ADT significantly improved overall survival compared with placebo + ADT, with median overall survival more than 6 years in the Apalutamide + ADT group and 14 months improvement over placebo + ADT.
Benefit from Apalutamide was observed despite a 19% crossover from placebo.
The safety profile of Apalutamide was consistent with prior interim analyses. ( Xagena )

Source: American Society of Clinical Oncology ( ASCO ) Virtual Meeting, 2020



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