Introduction: Prostate-specific antigen (PSA) isoforms, including a panel of four kallikrein markers, improve the prediction of high-grade prostate cancer in clinical studies and may potentially mitigate biopsy after prostate cancer screening. We evaluated determinants of real-world use of a commercially available four kallikrein marker panel (4Kscore®), and subsequent use of prostate biopsy among tested patients.
Methods: We queried the linked Surveillance, Epidemiology and End-Results Medicare database to identify a cohort of patients without a diagnosis of prostate cancer at the time of PSA testing in 1/2016-6/2019. Among patients receiving PSA screening, we evaluated clinical and sociodemographic factors associated with subsequent 4Kscore testing using descriptive statistics and multivariable generalized estimating equation models accounting for both sample weighting and repeated PSA testing events within patients. We compared the use of prostate biopsy and prostate cancer detection among 4Kscore tested versus untested patients.
Results:
Results: We identified a weighted sample of 3,892,492 PSA testing events, of which 10,195 were followed by 4Kscore testing (0.26%) within six months. The majority (97%) of 4Kscore tests were associated with an elevated PSA diagnosis. Beneficiaries who received 4Kscore testing were younger compared with those who did not undergo 4Kscore testing (mean 72.4 versus 74.2 years, p<0.001). In multivariable analysis, older age (odds ration [OR] = 0.13, 95% confidence interval [CI]: 0.08-0.21 for age 80+ versus 66-69 years), dual Medicaid eligibility (OR=0.61, 95% CI: 0.41-0.92), residence in higher poverty level zip codes (OR=0.55, 95% CI: 0.40-0.76 for =20% poverty vs <5%), and more comorbidities (OR=0.74, 95% CI: 0.62-0.90 for 1-2 versus 0 comorbidities) were associated with lower odds of 4Kscore testing. Within 6-months of PSA screening, 31% of patients who received 4Kscore testing (31%) underwent a prostate biopsy. This study is limited by absence of PSA values and clinical findings, which may influence the decision for both 4Kscore testing and biopsy.
Conclusions: 4Kscore testing was used in a small proportion of older Americans screened for prostate cancer. In this setting, most patients undergoing 4Kscore testing for an elevated PSA did not undergo a subsequent prostate biopsy.
Source of Funding: William O. Seery Foundation, Patterson Trust Research Award
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