SUMMARY: Prostate cancer is the most common cancer in American men with the exclusion of skin cancer, and 1 in 8 men will be diagnosed with prostate cancer during their lifetime. It is estimated that in the United States, about 299,010 new cases of prostate cancer will be diagnosed in 2024 and 35,250 men will die of the disease.
PSA (Prostate Specific Antigen) is one of the most widely used prostate cancer biomarkers, and the widespread use of PSA testing in the recent years has resulted in a dramatic increase in the diagnosis and treatment of prostate cancer. The management of clinically localized prostate cancer that is detected based on PSA levels remains controversial, and management strategies for these patients have included Surgery, Radiotherapy or Active Monitoring. However, it has been proposed that given the indolent nature of prostate cancer in general, majority of the patients do not benefit from treatment intervention and many patients die of competing causes. PSA test CANNOT distinguish between aggressive and benign cancer. As a result, many men have to undergo unnecessary follow-ups with a biopsy of the prostate. Further, treatment intervention can result in adverse effects on sexual, urinary, or bowel function. PSA test is also difficult to interpret, and PSA elevation can be associated with several non-malignant conditions such as older age, infection, inflammation and Benign Prostatic Hypertrophy. The U.S. Preventive Services Task Force (USPSTF) has recommended that population screening for prostate cancer with PSA should not be adopted as a public health policy, because the risks appeared to outweigh benefits, from detecting and treating PSA-detected prostate cancer.
Stockholm3 is a blood test that combines 5 protein biomarkers, 101 genetic markers, and clinical data with an advanced algorithm, in order to detect almost 100% of aggressive prostate cancers at an early stage. The Stockholm3 test has been validated in over 75, 000 men and has been used in health systems in Sweden, Norway, Finland, Germany, Switzerland, UK and Turkey, and results have been published in international peer-reviewed journals. Evidence suggests that Stockholm3 is more effective at predicting risk than PSA testing alone, for men aged 45-74 with PSA of at least 1.5ng/ml. Several studies have shown that the application of this test can reduce the number of biopsies by 32%, without compromising the diagnostic capacity of intermediate grade prostate cancers (Gleason 7 or higher), in comparison with the use of the PSA value 3 ng/ mL as cut-off value for biopsy recommendation. However, none of the validation studies included ethnically diverse population.
SEPTA is a prospective trial conducted to validate Stockholm3 in an ethnically diverse population, for prostate cancer risk stratification, and determine whether it could achieve noninferior sensitivity and superior specificity in this diverse population. This trial included men who were referred for prostate biopsy at North American sites from 2019 to 2023. Study participants had no previous diagnosis of prostate cancer. This study also used bio-banked specimens from 2008 to 2020. The cohort comprised 912 enrolled men and 1,217 with bio-banked blood. The median age was 63 years, 46% were White, 24% Black, 16% Asian and 14% were Hispanic.
This trial had 2 prespecified Primary goals: 1) Demonstrate noninferiority of the test in detecting Clinically Significant Prostate Cancer (defined as Gleason Grade group 2 or more), compared to PSA testing. 2) Prove superior specificity of the test versus PSA testing, thereby reducing the number of biopsies in men with benign or Gleason Grade group 1 biopsies. A Secondary goal was to evaluate Stockholm3 and PSA across ethnic subgroups. The study assessed Stockholm3 performance using prespecified thresholds and compared it to PSA across different ethnic subgroups. Statistical analysis plans were established before data analysis.
It was noted that the median PSA and Stockholm3 values among the participants were 6.1 ng/mL and 17, respectively. A total of 16% underwent MRI-targeted biopsies, and 20% had a prior benign biopsy. On biopsy, 29% were diagnosed with Clinically Significant Prostate Cancer, 14% with Gleason Grade group 1 cancer, and 57% with benign findings. The detection rate for Clinically Significant Prostate Cancer varied across ethnic groups: African American/Black (37%), White/Caucasian (28%), Hispanic/Latino (29%), and Asian (21%).
Overall, Stockholm3 value 15 or higher demonstrated noninferiority to a PSA value of 4 ng/mL or higher and nearly three times superior specificity. These results were consistent across ethnic subgroups. The researchers noted that using a Stockholm3 value of 15 or higher would have reduced benign and Gleason Grade group 1 biopsies by 45% overall and between 42-52% across ethnic subgroups, compared to PSA of 4 ng/ml or higher.
The study concluded that in an ethnically diverse population, Stockholm3 could significantly reduce unnecessary biopsies and diagnoses of low-grade tumors, while maintaining similar sensitivity to PSA, for detecting Clinically Significant Prostate Cancer. The results suggest that
Stockholm3 could improve risk stratification and reduce harms associated with prostate cancer screening in diverse populations.
Stockholm3 validation in a multi-ethnic cohort for prostate cancer (SEPTA) detection: A multicentered, prospective trial. Vigneswaran HT, Eklund M, Discacciati A, et al. J Clin Oncol 42, 2024 (suppl 4; abstr 262). DOI 10.1200/JCO.2024.42.4_suppl.262. Abstract#262.
