Early National Dissemination of Abiraterone and Enzalutamide for Advanced Prostate Cancer in Medicare Part D

Patterns of Care for Medicare Beneficiaries With Metastatic Prostate Cancer

INTRODUCTION

Therapeutic options for men with metastatic prostate cancer have increased in the past decade. We studied recent treatment patterns for men with metastatic prostate cancer and how treatment patterns have changed over time.

METHODS

Using the Surveillance, Epidemiology, and End Results‒Medicare database, we identified fee-for-service Medicare beneficiaries who either were diagnosed with metastatic prostate cancer or developed metastases following diagnosis, as indicated by the presence of claims with diagnoses codes for metastatic disease, between 2007 and 2017. We evaluated treatment patterns using claims.

RESULTS

We identified 29,800 men with metastatic disease, of whom 4721 (18.8%) had metastatic disease at their initial diagnosis. The mean age was 77 years, and 77.9% of patients were non-Hispanic White. The proportion receiving antineoplastic agents within 3 years of the index date increased over time (from 9.7% in 2007 to 25.9% in 2017; P < .001). Opioid use within 3 years of prostate cancer diagnosis was stable during 2007 to 2013 (around 73%) but decreased through 2017 to 65.5% (P < .001). Patients diagnosed during 2015 to 2017 had longer median survival (32.6 months) compared to those diagnosed during 2007 to 2010 (26.6 months; P < .001).

CONCLUSIONS

Most metastatic prostate cancer patients do not receive life-prolonging antineoplastic therapies. Improved adoption of effective cancer therapies when appropriate may increase length and quality of survival among metastatic prostate cancer patients.

In-office dispensing of oral targeted agents by urology practices in men with advanced prostate cancer

BACKGROUND

Management of men with advanced prostate cancer has evolved to include urologists, made possible by oral targeted agents (eg, abiraterone or enzalutamide) that can be dispensed directly to patients in the office. We sought to investigate whether this increasingly common model improves access to these agents, especially for Black men who are historically undertreated.

METHODS

We used 20% national Medicare data to perform a retrospective cohort study of men with advanced prostate cancer from 2011 through 2019, managed by urology practices with and without in-office dispensing. Using a difference-in-difference framework, generalized estimating equations were used to measure the effect of in-office dispensing on prescriptions for abiraterone and/or enzalutamide, adjusting for differences between patients, including race.

RESULTS

New prescription fills for oral targeted agents increased after the adoption of in-office dispensing (+4.4%, 95% confidence interval [CI] = 3.4% to 5.4%) relative to that for men managed by practices without dispensing (+2.4%, 95% CI = 1.4% to 3.4%). The increase in the postintervention period (difference-in-difference estimate) was 2% higher (95% CI = 0.6% to 3.4%) for men managed by practices adopting dispensing relative to men managed by practices without dispensing. The effect was strongest for practices adopting dispensing in 2015 (difference-in-difference estimate: +4.2%, 95% CI = 2.3% to 6.2%). The effect of dispensing adoption did not differ by race.

CONCLUSION

Adoption of in-office dispensing by urology practices increased prescription fills for oral targeted agents in men with advanced prostate cancer. This model of delivery may improve access to this important class of medications.

Comparison of out-of-pocket costs and adherence between the two arms of the prospective, randomized abiraterone food effect trial

PURPOSE

Abiraterone acetate, prescribed for metastatic prostate cancer, has enhanced absorption with food. This effect was exploited in a randomized trial which showed noninferiority of PSA decline for 250 mg abiraterone with a low-fat meal (LOW) compared to 1,000 mg abiraterone fasting (STD). Drug was obtained via patient insurance. Patient out-of-pocket costs and adherence were surveyed.

METHODS

Trial participants were randomized to STD or LOW, and surveys of adherence and out-of-pocket costs were administered at baseline and just before coming off study (follow-up).

RESULTS

Out-of-pocket costs were available from 20 of 36 STD and 21 of 36 LOW patients. Median out-of-pocket costs for a month of drug were $0 (LOW) and $5 (STD); mean costs were $43.61 (LOW) and $393.83 (STD). The two groups did not differ significantly (p = 0.421). Maximum out-of-pocket cost was $1,000 (LOW) and $4,000 (STD). Monthly out-of-pocket costs > $500 were found in 1 LOW and 5 STD patients. For adherence, only 11 STD and 19 LOW patients had questionnaires completed at both baseline and follow-up. STD adherence was 98.18% at baseline and 91.69% at follow-up, differing significantly (p = 0.0078). LOW adherence was 96.52% at baseline and 97.86% at follow-up, not differing significantly (p = 0.3511). Adherence did not correlate with demographics. At follow-up, increasing adherence correlated significantly with decreasing dose (p = 0.013; rho =  - 0.458).

CONCLUSIONS

Out-of-pocket costs did not differ significantly in this limited analysis. Adherence was significantly different in STD as the trial progressed, which was not found in LOW.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01543776; registered March 5, 2012.

Outcomes Among African American and Non-Hispanic White Men With Metastatic Castration-Resistant Prostate Cancer With First-Line Abiraterone

IMPORTANCE

Prospective evidence suggests abiraterone is associated with superior progression-free survival for African American men compared with non-Hispanic White men with metastatic castration-resistant prostate cancer (mCRPC).

OBJECTIVE

To investigate differences in outcomes with first-line abiraterone therapy between African American and non-Hispanic White men with mCRPC in a national real-world cohort.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study used a nationwide electronic health record-derived database of 3808 men receiving first-line therapy for mCRPC between January 1, 2012, and December 31, 2018. Data analysis was performed between January 1, 2020, and June 1, 2021. Median follow-up was 13 months (IQR, 7-22 months). Propensity score-based inverse probability of treatment weighting was applied to reduce imbalance in measured confounders between patients receiving first-line abiraterone vs other first-line therapies. Deidentified patient data originated from a geographically diverse set of approximately 280 cancer clinics (approximately 800 sites of care) throughout the United States. Participants had newly diagnosed mCRPC and were receiving first-line systemic therapy during the study period.

EXPOSURES

Receipt of abiraterone for first-line therapy.

MAIN OUTCOMES AND MEASURES

Overall survival from start of first-line treatment. Stratified analyses investigated overall survival within each race group, with first-line enzalutamide as the comparator.

RESULTS

Among 3808 patients with mCRPC, there were 2615 non-Hispanic White men (68.7%; mean [SD] age at diagnosis, 74 [8] years) and 404 African American men (10.6%; mean [SD] age at diagnosis, 69 [9] years), and 1729 patients (45.4%) in the cohort received first-line abiraterone. Among patients receiving first-line abiraterone, African American men had higher median overall survival than non-Hispanic White men (23 months [IQR, 10-37 months] vs 17 months [IQR, 9-32 months], respectively; inverse probability of treatment weighting hazard ratio, 0.76; 95% CI, 0.60-0.98). A race-by-treatment interaction existed for first-line abiraterone vs first-line enzalutamide (hazard ratio for abiraterone vs enzalutamide: non-Hispanic White men, 1.21 [95% CI, 1.06-1.38]; African American men, 1.05 [95% CI, 0.74-1.50]; interaction P = .02). There was no overall survival difference between first-line abiraterone and first-line enzalutamide among African American patients (24 vs 24 months, respectively; inverse probability of treatment weighting hazard ratio, 1.05; 95% CI, 0.74-1.50). First-line abiraterone was associated with decreased median overall survival relative to first-line enzalutamide among non-Hispanic White patients (17 months [IQR, 9-32 months] vs 20 months [IQR, 10-36 months], respectively; inverse probability of treatment weighting hazard ratio, 1.21; 95% CI, 1.06-1.38).

CONCLUSIONS AND RELEVANCE

In this cohort study of patients who received first-line systemic therapy for mCRPC, African American men who received abiraterone had improved overall survival compared with non-Hispanic White men. Future prospective studies should assess drivers of differential abiraterone outcomes in mCRPC between African American and non-Hispanic White men, including differences in genetic factors and socioeconomic status, to inform treatment strategies.

Adoption of Abiraterone and Enzalutamide by Urologists

OBJECTIVE

To investigate the adoption of abiraterone and enzalutamide by urologists. Abiraterone and enzalutamide are oral therapies approved for the treatment of metastatic castration-resistant prostate cancer, a disease most commonly treated by medical oncologists.

METHODS

Using the Medicare Part D Public Use Files from 2013 to 2016, we identified total abiraterone and enzalutamide prescriptions 2013-2016 and urologists who prescribed moderate to high volumes of these drugs. We then characterized the urologist practices of those urologists according to practice context (eg, single-specialty group) using data from the Centers for Medicare and Medicaid Services, and the geographic distribution of those providers.

RESULTS

We found abiraterone prescriptions increased from 71,423 in 2013 to a peak of 100,371 in 2015 and enzalutamide prescriptions continued to increase from 29,572 in 2013 to 100,980 in 2016. Prescriptions by urologists increased between 2013 and 2016 while prescriptions by other specialties plateaued. The number of moderate-high prescribing urologists increased from 98 (abiraterone) and 22 (enzalutamide) in 2013, to 301 (abiraterone) and 671 (enzalutamide) by 2016 with 1063 unique urologists prescribing moderate-high volumes of either drug between 2013 and 2016. Among urologists who prescribe androgen deprivation therapy, 5% were moderate-high prescribers of abiraterone and 12% of enzalutamide in 2016. The majority of moderate-high prescribing urologists were in single-specialty groups (70%).

CONCLUSION

Urologists are increasingly prescribing oral therapies for metastatic castration-resistant prostate cancer. Understanding the distribution of urologists specializing in castration-resistant prostate cancer therapeutics will help guide future interventions to optimize the care for this important patient population.

Prospective International Randomized Phase II Study of Low-Dose Abiraterone With Food Versus Standard Dose Abiraterone In Castration-Resistant Prostate Cancer

Purpose Abiraterone acetate (AA) is a standard of care for metastatic castration-resistant prostate cancer (CRPC). Despite a large food effect, AA was administered under fasting conditions in its pivotal trials. We sought to test the hypothesis that low-dose AA (LOW; 250 mg with a low-fat meal) would have comparable activity to standard AA (STD; 1,000 mg fasting) in patients with CRPC. Patients and Methods Patients (n = 72) with progressive CRPC from seven institutions in the United States and Singapore were randomly assigned to STD or LOW. Both arms received prednisone 5 mg twice daily. Prostate-specific antigen (PSA) was assessed monthly, and testosterone/dehydroepiandrosterone sulfate were assessed every 12 weeks with disease burden radiographic assessments. Plasma was collected for drug concentrations. Log change in PSA, as a pharmacodynamic biomarker for efficacy, was the primary end point, using a noninferiority design. Progression-free survival (PFS), PSA response (≥ 50% reduction), change in androgen levels, and pharmacokinetics were secondary end points. Results Thirty-six patients were accrued to both arms. At 12 weeks, there was a greater effect on PSA in the LOW arm (mean log change, -1.59) compared with STD (-1.19), and noninferiority of LOW was established according to predefined criteria. The PSA response rate was 58% in LOW and 50% in STD, and the median PFS was approximately 9 months in both groups. Androgen levels decreased similarly in both arms. Although there was no difference in PSA response or PFS, abiraterone concentrations were higher in STD. Conclusion Low-dose AA (with low-fat breakfast) is noninferior to standard dosing with respect to PSA metrics. Given the pharmacoeconomic implications, these data warrant consideration by prescribers, payers, and patients. Additional studies are indicated to assess the long-term efficacy of this approach.

Temporal and geographic variation in the systemic treatment of advanced prostate cancer

BACKGROUND

Several systemic treatments have been shown to increase survival for patients with metastatic castration-resistant prostate cancer. This study sought to characterize variation in use of the six "focus drugs" (docetaxel, abiraterone, enzalutamide, sipuleucel-T, radium-223, and cabazitaxel) that have been approved by the Food and Drug Administration for the treatment of metastatic castration-resistant prostate cancer during the years 2010-2015. We hypothesized that the use of these treatments would vary over time and by region of the country.

METHODS

We used Clinformatics DataMart™ Database (OptumInsight, Eden Prairie, MN), a de-identified claims database from a national insurance provider. Our sample included patients with prostate cancer who received any of the six drugs. We describe changes in usage patterns over time and geographic region of the United States via detailed descriptive statistics. We explore both patterns of first line therapy and sequence of treatments in our database.

RESULTS

Our final analysis included 4275 patients with a mean age of 74 years. Docetaxel was the most commonly used first-line therapy in 2010 (97%), 2011 (66%), and 2012 (49%). Abiraterone was the most commonly used first-line therapy in 2013 (56%), 2014 (46%), and 2015 (34%). Approximately 14% of our study cohort received ≥3 of the 6 drugs throughout their disease course. There was marked geographic variation in use of each of the drugs.

CONCLUSION

Variation in treatment patterns were found with respect to both time and geographic location. Prescription rates of abiraterone outpaced docetaxel as the most commonly prescribed drug after 2013 when it became widely available. However, some regions of the country still lagged behind and prescribed less than would be expected.