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Real-World Prostate-Specific Antigen Response and Treatment Adherence of Apalutamide in Patients with Non-Metastatic Castration-Resistant Prostate Cancer - Beyond the Abstract

Since its FDA approval in 2018, apalutamide, a next-generation androgen signaling inhibitor, has contributed to an improved standard of care for patients with with non-metastatic castration-resistant prostate cancer (nmCRPC). Left unchecked, nmCRPC can progress to metastatic castration-resistant prostate cancer (mCRPC);1 thus, therapies targeting nmCRPC have the potential to extend survival by preventing or delaying metastasis. Such early disease control has a significant impact on prostate cancer patient disease burden, as prostate cancer is the second-most common cause of death for men in the United States.2

Apalutamide received its first US FDA approval based on the results of the phase 3 SPARTAN clinical trial, which showed that patients with nmCRPC who were treated with apalutamide had a median metastasis-free survival of 40.5 months, compared with 16.2 months for those receiving placebo.3 Despite the outstanding clinical trial results, real-world data reports on the efficacy of apalutamide have been limited. This retrospective longitudinal cohort study of patients from 63 urology practices across the U.S. provides additional insight into the real-world use of apalutamide for the treatment of nmCRPC.

This study evaluated serum prostate-specific antigen (PSA) levels – an early indicator of treatment response, and adherence to therapy in 193 men with nmCRPC who initiated apalutamide in a clinic with in-office dispensing capabilities (Specialty Networks).4 Importantly, this real-world study also assessed these measures in Black men, a population commonly under-represented in cancer clinical trials.5

Understanding how medications perform in real-world populations is important information for treating- physicians, since patient populations and treatment protocols in clinical trials may not always reflect real-world findings. For example, registrational clinical trials require that patients take their medication according to the trial schedule, and this medication adherence is closely monitored, while in the real-world, variation in adherence to therapy may occur. Likewise, clinical trial populations may not reflect the patient heterogeneity observed in real-world medical practice. While the SPARTAN trial population consisted of 6% Black patients - a percentage under-representing the proportion of Black males in the U.S. population6 - furthermore, there has been scientific debate as to whether the natural course of prostate cancer progression differs in Black and non-Black men, either because of biochemical determinants of disease or because of other factors such as social determinants of health.5

This is the first study to assess the real-world treatment response to apalutamide in Black patients with nmCRPC. Before initiating apalutamide, mean PSA levels were 7 ng/mL in the entire study cohort; however, mean baseline PSA levels of Black patients (10.5 ng/mL) were observed to be higher than in the non-Black patients (5.6 ng/mL). Despite higher levels of PSA in black patients prior to initiating apalutamide, baseline PSA doubling times were similar in Black and non-Black patients (10.1–10.8 months) before initiating apalutamide. Patients in the study were treated with apalutamide for approximately 12 months on average.4 In this study, the definition of PSA response was similar to that used in SPARTAN, and importantly, the proportion of the overall population achieving a PSA response in this real-world group of patients (86%) was similar to the proportion achieving a PSA response in SPARTAN (90%).3 After initiation of apalutamide, 93.1 % of Black patients and 85.9% of non-Black patients achieved at least a 50% decline in PSA from their pre-apalutamide PSA test value at baseline.4


This study also found that rates of adherence to taking apalutamide (medication possession ratio) was similar between Black (90.1%) and non-Black patients (94.5%) over the follow-up period. A higher proportion of Black patients (78.9%) was observed to refill their medication as prescribed and without a refill gap greater than 90 days compared to non-Black patients (65.7%).4

According to Janssen Oncology President Tyrone Brewer, “Real-world analyses such as this demonstrate Janssen’s commitment to prostate cancer, and a patient-centered mission to better serve all patients and eliminate health disparities, especially in those at greatest risk.”

Written by: Neal Shore, MD, FACS, Chief Medical Officer of Surgical Oncology and Urology at GenesisCare US; Director, Carolina Urologic Research Center, Myrtle Beach, SC

References:

  1. Saad et al. “The 2015 CUA-CUOG Guidelines for the management of castration-resistant prostate cancer (CRPC).” Canadian Urological Association journal = Journal de l'Association des urologues du Canada vol. 9,3-4 (2015): 90-6. doi:10.5489/cuaj.2526. Accessed April 2022.
  2. American Cancer Society. Key Statistics for Prostate Cancer. https://www.cancer.org/cancer/prostate-cancer/about/key-statistics.html. Accessed April 2022.
  3. ERLEADA® U.S. Prescribing Information. Accessed April 2022.
  4. Lowentritt et al. Real-World Effectiveness and Treatment Adherence of Apalutamide in Non-Metastatic Castration-Resistant Prostate Cancer Patients. Urology. 2022 Mar 19: S0090-4295(22)00245-X. doi: 10.1016/j.urology.2022.02.024. Accessed April 2022.
  5. American Cancer Society. Cancer Facts & Figures for African American/Black People 2022-2024. Available at: https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/cancer-facts-and-figures-for-african-americans/2022-2024-cff-aa.pdf. Accessed April 2022
  6. United Sates Census Bureau. Quick Facts. Available at:  https://www.census.gov/quickfacts/fact/table/US/PST045221. Accessed April 2022.

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