The IsoPSA test will be considered medically reasonable and necessary when
all the following are met:

Testing of men 50 years of age and older who have a **confirmed*** moderately
elevated PSA (greater than 4 and  25 ng/mL)

**AND**

No other relative contraindication for prostate biopsy including:

      * Less than a 10-year life expectancy

*PSA elevation should be verified after a few weeks under standardized conditions (e.g., no ejaculation, manipulations, and urinary tract infections) in the same laboratory or other CLIA approved laboratory before considering a biopsy.

**_Background_**

Screening modalities for prostate cancer(PCA) include digital rectal exam
(DRE) and prostate-specific antigen (PSA) test at a frequency of every twelve
months for men ages fifty and over in effort to detect increased risk for
adenocarcinoma of prostate.1 PSA is a reliable immunocytochemical marker for
adenocarcinoma of the prostate. However, screening and early treatment of
prostate cancer have come under scrutiny due to concerns for over diagnosis of
low-risk cancers.2 Guidelines have been updated due to studies to refine the
use of PSA, which remains the primary screening test.1-3 Investigations into
adjunctive testing may provide opportunities to avoid biopsies and reduce
overdiagnosis.2

IsoPSA is a blood-based single parameter, structure-based assay for improved
detection of high-grade prostate cancer. The test partitions isoforms of
prostate-specific antigen with an aqueous two-phase reagent.4 The test aims to
improve specificity by testing specific changes in PSA that arise specifically
in cancer cells and would not be affected by conditions such as prostate
hyperplasia, inflammation, or age that reduce the specificity of the standard
PSA assays.4



**_Evidence Review_**

Klein et al.4 2017 was an industry-sponsored multi-centered prospective study
that included 261 men scheduled for prostate biopsy due to rising PSA level or
suspicious digital rectal exam. The study was conducted at five different
academic and community centers within the United States over 15 months. The
primary study endpoint was the presence or absence of cancer and cancer grade
as detected by ultrasound or MRI fusion biopsy. Exclusion criteria included
serum PSA<2 ng/ml; recent (<72 hours) prostate manipulation, including DRE;
recent (<2 weeks) urinary tract infection and/or prostatitis; recent (<30
days) prostate surgery, urinary catheterization, prostate infarction, or
endoscopic evaluation; and other urinary tract malignancy. Out of 434 samples
collected, 173 were excluded. Reasons for exclusion included prolonged storage
greater than ninety days, canceled biopsies, the breach of sample collection
protocol, shipping delays, or not meeting study protocol.

The research aimed to assess two clinical performance objectives: the
discriminatory power between malignant and non-malignant prostate conditions
and between high-grade and low-grade cancers versus benign pathology. This
population had an overall prevalence of 53% for prostate cancer, with 33.7% of
cancers considered high-grade. They utilized receiver operating characteristic
analysis to determine the discriminatory power measurement. In this
preliminary analysis, they utilized decision curve analysis to access the
clinical utility of the models by comparing the two extremes, no biopsy to
biopsy for all (current patient cohort), and comparison against the modified
prostate cancer prevention trial risk calculator 2.0. They reported results
were: "for cancer versus no cancer endpoint, the area under the curve (AUC)
was 0.79 (95% CI 0.73-0.84) for IsoPSA versus 0.61 (95% CI 0.54-0.67) for
total PSA (p < 0.001). For high-grade cancer versus low-grade cancer/benign
histology, the AUC was 0.81 (95% CI 0.74-0.86) for IsoPSA versus 0.69 (95% CI
0.61-0.75) for total PSA (p < 0.005)". Using the pre-selected cutoff to
recommend a biopsy, they reported a 48% reduction in false-positive biopsies
with IsoPSA. Utilizing a cutoff selected to identify men at low risk of high-
risk disease, they reported a 45% reduction in the false-positive rate. They
acknowledged that the test was not yet validated. The authors conclude that
IsoPSA outperformed PSA in predicting prostate cancer risk.

The authors acknowledge that clinical and demographic parameters including
age, race, and prostate volume could impact the clinical performance of the
IsoPSA test was not evaluated in this study which focused on the test's
clinical performance. They also acknowledge weaknesses in the study, including
lack of central or standardized pathology review of the biopsies, a lack of
distinction between primary and repeat biopsies, and variability in the use of
MRI for decisions on the need for in the technique used in biopsies.
Additional weakness includes the study design was a prospective trial without
controls. This was not designed or powered for superiority, although the
authors suggest the test outperformed standard PSA test. Age, race, prostate
volume, presence of benign prostatic hypertrophy (BPH) was not evaluated but
could impact results. Various pathological labs and methods for biopsy may
have some variability that was not controlled, introducing a risk of bias.

Stovsky et al. 20195 was **** an industry-sponsored multi-centered prospective
validation study. Two hundred seventy-one men scheduled for prostate biopsy
due to rising PSA or suspicious DRE over a ten-month period from seven
academic and community centers were included. Biopsies were performed under
ultrasound or MRI guidance. Exclusion criteria included: serum PSA less than 2
ng/ml; recent (less than 72 hours) prostate manipulation, including digital
rectal examination; recent (less than two weeks) urinary tract infection
and/or prostatitis; recent (less than 30 days) prostate surgery, urinary
catheterization, prostate infarction or endoscopic evaluation; and any other
urinary tract malignancy. Three hundred five samples were collected with
thirty-four exclusions, including nine due to prolonged storage, forwarded
canceled biopsies and fifteen due to PSA <2 (exclusion), and six unrelated,
leaving a final cohort of 271.

The primary endpoint was the clinical performance of the test in
discriminating power of IsoPSA for the presence of high-grade prostate cancer
versus low-grade cancer or benign pathology. Using the data from Klein et al.4
a cutoff value of 17% was selected as the predicted probability of high-grade
prostate cancer. The authors concluded using a cutoff of 17% yielded 93%
negative predictive value. They calculate that this would reduce unnecessary
prostate biopsies by 43%. Using modeling, they estimate that out of 1000
subjects; the test would miss twenty-two high-grade cancers, of which seven
would have been Gleason sum 4 + 3 or higher. A sub-analysis of the African
American participants showed similar results to the original combined cohort.

Additional analysis on the biopsy technique segregated biopsies done by
ultrasound compared to MRI guidance. They observed significant improvement in
the IsoPSA AUC when the biopsies were performed under MRI guidance. The
number of biopsies done under MRI guidance increased from 4%4 to 41% in this
study.

Strengths of the study include using a new patient cohort, the addition of
sub-analysis for African Americans and based on biopsy type, test run in the
same lab, and pre-specified fixed outcome measurements defined by the
previously published study.

Weaknesses of this study include study design as a prospective trial without a
control group. While the authors state the test had superior performance to
PSA, the trial did not compare the performance of IsoPSA to PSA directly,
which would require an appropriately designed and powered superiority study or
non-inferiority study to demonstrate at least equally accurate. While the
study addressed the test's clinical performance (validity), it did not address
the clinical utility. The lack of standardized biopsy technique and lack of
central pathology review introduces a risk of bias. Age, prostate volume,
presence of BPH were not evaluated but could impact results. The authors
acknowledge a significant increase in MRI guidance for the biopsies, which is
more accurate than the ultrasound guidance and cannot exclude selection bias.

Scovell et al. 20216 conducted a real-world observational study aimed to
assess the impact of the IsoPSA test for prostate cancer risk assessment on
provider patient management decisions. A total of 38 providers enrolled 900
men being evaluated for prostate cancer. The inclusion criteria which were
defined as age _>_ 50 years, total serum prostate specific antigen [PSA] _>_ 4
and <100 ng/ml and no history of prostate cancer and IsoPSA indication for
use. Of the 900 patients enrolled, 734 established the final study cohort.
Providers recorded their intentions to recommend patients for biopsy and/or
magnetic resonance imaging (MRI), informed by all clinical data available at
the time prior to IsoPSA testing. After IsoPSA was obtained, results were
reported above or below an index threshold of 6.0, where an index 6.0 has a
90% negative predictive value for the absence of high-grade cancer (Gleason
grade group 2 or higher) and an index value >6.0 has a 48% positive predictive
value for the presence of high-grade cancer. Upon review of IsoPSA results,
providers confirmed or updated their recommendations for biopsy and MRI.

The primary outcome was to determine the clinical utility of IsoPSA based on
two things. One, provider willingness to use the test (test utilization) and
two, the change in provider behavior as assessed by how IsoPSA influenced
recommendations for biopsy and MRI. Consistency between IsoPSA results and
recommendations for prostate biopsy was also considered. Changes in
recommendations (either for or against) in 60.2% (442/734) for decisions on
prostate biopsy and 6.0% (44/734) for decisions on MRI resulted based on the
utilization of IsoPSA. Results included a 55% (284 vs 638) net reduction in
recommendations for prostate biopsy for men with total PSA _>_ 4 ng/ml who
underwent IsoPSA testing. A 9% reduction in recommendations for MRI was
observed. A correlation was observed between IsoPSA results and provider
recommendations for prostate biopsy, with 87% of patients with an IsoPSA
index above the threshold recommended for biopsy and 92% of patients with an
IsoPSA index below the threshold not recommended for biopsy.

Strengths of this study include a large number of providers representing real-
world clinical practice including a broad range of practice styles, education
and experience. Recruitment of patients ranged across varied practice
settings, and participating providers served as intra-provider and intra-
patient controls for both pre- and post-IsoPSA clinical decision making. A
standardized reporting module was utilized to record the influence of IsoPSA
on management decisions.

Limitations of this study include patient compliance with provider
recommendations for or against biopsy post-IsoPSA were not assessed, a lack
of long-term outcome data, and lack of a control group.

Cost analysis studies were excluded from evidence review.7

Klein et al. 2022 (10) conducted a prospective, multicenter study at eight
academic and community sites between August 2015 and August 2020. IsoPSA was
performed in 888 men _>_ 50 years with total PSA _>_ 4ng/ml scheduled for
prostate biopsy. The primary outcome of this study was to estimate the
performance, sensitivity, specificity, and predictive characteristics of
IsoPSA. Secondary outcomes were to identify the risk of High-Grade prostate
cancer (Gleason Score  7) and any PCa (Gleason Score  6) in men  50 years
of age with a pre-biopsy total PSA 4 ng/ml undergoing diagnostic biopsy and
to determine cancer status when tested per protocol. The secondary outcome was
to compare the diagnostic accuracy of IsoPSA to total PSA and percent free
PSA based on receiver operating characteristic (ROC) analysis. Exploratory
outcomes were to assess the performance of IsoPSA using ROC analysis in
subgroups with total PSA 4 to 10 ng/ml, total PSA > 10 ng/ml, and in relation
to prior biopsy status.

Results included a disease prevalence of 35.6% (High-Grade PCA) and 58.9% (any
PCA). The area under the ROC was 0.783 (High-Grade PCA) and 0.770 (any PCA).
The High-Grade PCA endpoint, AUC was 0.783 (95% CI 0.7520.814) for IsoPSA
vs. 0.672 (95% CI 0.6390.706) for total PSA and 0.724 (95% CI 0.690 0.758)
for percent free PSA (p< 0.001). An estimated 46% (High-Grade PCA) and 42%
(any PCA) of biopsies could be avoided in low-risk patients when utilizing
IsoPSA index cutoffs. Forty percent (354/888) subjects had a prior negative
biopsy. In the group with at least one prior biopsy, IsoPSA yielded a
moderate AUC (0.82), a modest specificity (46%) and a good NPV (95%) for high-
grade PCa on subsequent biopsy in 202 subjects with prior negative biopsies.
These findings suggest IsoPSA accuracy is not influenced by previous negative
biopsy. The study suggests that IsoPSA is unaffected by the use of alpha
blockers or 5-reductase inhibitors. The study data suggests that biopsy
should be performed regardless of MRI findings for an IsoPSA index >6 based
on the information that MRI misses 20% of high-grade cancers.

The authors report that IsoPSA maintained statical accuracy across a broad
range of elevated total PSA ranging from 4-100 ng/mL in 888 subjects. 24%
(217/888) of study subjects had a PSA >10 ng/mL. 54 subjects (14.8%) of the
sub-set with PSA >10-25 ng/mL had a negative biopsy while 44 (21.3%) has low
grade PCA and 96 (30.4%) had high-grade PCA. However, only 23 subjects or 2.5%
(23/888) had total PSA values >25 ng/mL with 20 of those predictably having
high grade PCA (Gleason >7). Specificity (SP) and NPV (negative predictive
value) decreased modestly in the group with total PSA >10 ng/mL and further
breakdown of the small sub-set with PSA> 25 (n=23) was not reported in the
study.

Strengths of this study include the prospective, multicenter design, the large
sample size, comparison of total and percent free PSA, and use of gold
standard prostate biopsy pathology comparison in all study participates.
Limitations include of this study include lack of standardized biopsy
techniques, decentralized pathology review, failure to account for false
positive IsoPSA or false negative biopsy results, lack of a control group,
lack of long-term follow-up and risk of bias due to funding by laboratory that
produces the test.

Benidir et al. is a single center retrospective review of prospectively
collected data from 2019-2021 following a consecutive cohort of 83 subjects
with elevated IsoPSA levels (>6) and concerning PSA and/or digital rectal
examination who had a prostate biopsy followed by radical prostatectomy (RP)
within the same period. 44 subjects without pre-operative IsoPSA served as
controls. Pre-operative prostate Magnetic Resonance Imaging (MRI) and adverse
histopathologic and MRI features when comparing biopsy to RP histopathology
were included in the analysis. Of the 83 subjects with elevated IsoPSA 82 had
PCa (99%) on final pathology. There were no differences in concordance,
downstaging, and upstaging GG rates from biopsy to RP between the IsoPSA group
and control, however the IsoPSA group had statistically significant elevation
in pre-operative PSA levels compared to the control group (7.8 ng/mL vs 5.2
ng/mL, respectively, P<.001). IsoPSA was not influenced by prostate MRI or
pathological features suggesting IsoPSA is non-selective marker. The authors
conclude elevated IsoPSA (>6) is a diagnostic tool that can detect clinically
significant prostate cancer at the time of biopsy.

Limitations include study design of retrospective review at a single center,
modest sample size for elevated IsoPSA outcomes, comparator group had
significantly lower IsoPSA values and there was a lack of a comparator group
of patients with low IsoPSA values who ended up undergoing biopsy and/or
eventual RP.9

National Comprehensive Cancer Network (NCCN) guidelines recommendations
include consideration for the use of biomarker tests for men with persistent
elevation in PSA between 3 to 10 ng/ml using a validated test (determined in
peer-reviewed, multi-site studies using an independent cohort of patients)
within the prostate cancer early detection algorithms.2,7 The algorithms
breakdown the role of these test by age, risk factors for prostate cancer, and
if the test is used to evaluate for possible initial biopsy versus management
of biopsy results. As of 02/16/2022, they included percent-free PSA, 4Kscore,
PHI, PCA3, ConfirmMDx, MPS, and IsoPSA in the guidelines.9

U.S. Preventive Service Task Force Guidelines updated in 2018 recommend PSA
screening with a "C" recommendation and did not mention adjunctive screening
test.3

The American Urological Association (AUA) states that PSA derivatives and
isoforms and novel urinary markers and biomarkers for screening with the goal
of reducing prostate cancer mortality provide limited evidence to draw
conclusions and should not be used for primary screening. Additionally, the
use of these markers after PSA screening may be considered a secondary test
for informed decisions making regarding the need for prostate biopsy or repeat
biopsies, but "emphasized the lack of evidence that these tests will increase
the ratio of benefit to harm".10





IsoPSA aims to improve the existing standard of care PSA testing for the
detection of high-grade prostate cancer. CGS released a non-coverage LCD draft
in October 2021. Since that time, clinical utility data has been published and
NCCN guidelines have been updated to include IsoPSA. One of the initial
concerns addressed in the draft LCD was while the test offered a 93%
sensitivity, resulting in approximately twenty-two missed cancers in 1000
patients based on the mathematical models, there was uncertainty if this would
provide confidence to providers to be comfortable not performing a biopsy.4,5.
In Scovell et al.6 changes in recommendations were reported in 60.2% for
decisions on prostate biopsy resulting in a 55% net reduction in
recommendations for prostate biopsy demonstrating confidence in this real-
world population to utilize the test in decision making. In addition, this
study provides the clinical utility data that was previously lacking. At the
time of the open meeting in June 2022 the impact of age, prostate volume, and
comorbid conditions as well as use outside of the initial biopsy had not been
investigated. Since the June 2022 meeting additional literature has been
published that addresses the accuracy of IsoPSA in men with BPH and on
5-APIs, prior initial biopsies, and a broader range of PSA levels (10). Based
on this latest information, the restriction for benign disease and prior
negative biopsies was removed. The range of PSA was expanded to allow baseline
PSA levels from 4-25 ng/mL. However, we did not agree with expansion in the
baseline PSA range of 26-100 ng/mL due to poor strength of data to support
this range and concern for lack of long-term data on outcomes for missed
cancers. The NCCN algorithm includes IsoPSA test for use outside the areas
investigated in the IsoPSAstudies, and CGS does not consider the use outside
the population studied applicable. The limited coverage criteria align with
the population studied in the IsoPSA literature.