Current molecular biomarker tests that risk stratify individuals with
cutaneous squamous cell carcinoma (cSCC) are non-covered by this contractor.

**Clinical Background**



Cutaneous squamous cell carcinoma (cSCC) is an epidermal keratinocyte-derived
malignancy that is the second most common skin cancer.1,2 Incidence is
increasing and varies with latitude in the United States, with higher
incidence in areas of greater sun exposure.3 Each year, over 700,000 new cases
are diagnosed, 5600 to 12,600 patients develop nodal metastasis, and there are
4000-8800 deaths.2,4-7 Incidence is highest in non-Hispanic white populations,
greater in males compared to females, and increases with age for a mean age at
diagnosis of approximately 71 years.3 Ultraviolet (UV) radiation due to
cumulative and chronic sun exposure is the most important environmental risk
factor, occurring more frequently in those with less pigmented skin types.8-10
In individuals with highly pigmented skin, cSCC is more frequently found on
non-sun exposed areas and is often associated with chronic inflammation,
chronic wounds, or scarring.4-7 cSCC of this etiology is more difficult to
treat and exhibits a higher recurrence risk.11-13



The overall prognosis is favorable with a 5-year survival of approximately
98%.2,8,14 While most tumors are easily cured with surgical excision, a subset
result in recurrence, metastasis, and disease-specific death.14,15 The risk of
nodal metastasis ranges from 1.2-5.8% in cohort and tumor registry studies and
risk of death is approximately 2%.14,16,17 In a cohort of patients treated
with Mohs micrographic surgery (MMS), the rate of local recurrence was 2.5%,
metastatic disease 1.9% and of disease-specific death 0.57%,18 underscoring
the importance of adequate surgical treatment.



**Approaches to Risk-Stratification and Staging**



Significant effort has been placed on identifying tumors likely to result in
poor outcomes (high-risk cSCC) through development of risk stratification or
staging systems that lead to a more individualized, risk-based treatment
approach and follow-up schedule.19-25 However, this has not been defined
consistently and currently available approaches have limited positive
predictive value (PPV).14,16,26 The most utilized staging systems and
guidelines include the National Comprehensive Cancer Network (NCCN)
Guidelines, the American Joint Committee on Cancer 8th Edition (AJCC 8)
staging system for Head and Neck Tumors, and the Brigham and Women's Hospital
staging system (BWH).16,27 Each will be discussed in brief.



As of 2021, the NCCN guidelines risk stratify cutaneous squamous cell cancer
into low, high and very high-risk groups based on outcomes.8 The high-risk
group is at increased risk of local recurrence and the very high-risk group is
at increased risk of both local recurrence and metastasis.8 This
stratification was validated by a large retrospective dual-center cohort,
comparing outcomes of each group in patients treated with MMS or wide local
excision (WLE). The cohort included 12,684 primary tumors from 8727 patients,
which were subsequently stratified by NCCN guidelines into low, high, and very
high-risk groups.28



Patients with NCCN very high-risk cSCC tumors experienced worse outcomes
compared to patients with high-risk and low risk tumors in terms of local
recurrence (LR) (11.2% vs 2.0% and 0.7%, p< 0.001), nodal metastasis (NM)
(8.9% vs 0.7% and 0.1%, p< 0.001), in transit metastasis (ITM) (4.1% vs 0.3%
and 0.0%, p< 0.001), distant metastasis (DM) (5.4% vs 0.3% and 0.0%, p<
0.001), disease specific death (DSD) (10.2% vs 0.7% and 0.3%, p< 0.001), and
any poor outcome (17.7% vs 1.8% and 0.3%, P< 0.001).28 The study also
demonstrated that MMS results in better local recurrence and distant
metastasis outcomes compared to WLE after adjusting for NCCN risk groups, age
and sex.28



The AJCC 8 came into clinical use in January 2018 with an updated four T stage
(T1-T4) cSCC tumor classification for cases located on the head and neck; it
was validated by multiple studies.16,26,29,30 Tumors are considered high-risk
when staged as T3 or T4, and most high-risk tumors are staged as T3 due to
relative rarity of T4 cases.31 More recently, in order to further reduce the
prognostic heterogeneity of AJCC 8, the Salamanca refinement of the T3
classification was proposed, with significant difference in outcomes across
three groups within T3.32 The BWH staging system was developed in 2013 to
provide superior prognostic value compared to an earlier version of AJCC
Staging (AJCC 7).26,32,33 In AJCC7, higher tumor classes (T3 and T4) required
the rare finding of bone invasion, and thus most poor outcomes occurred in
stage T2.26,34 BWH staging consists of four T stages (T1, T2a, T2b, and T3)
and categorizes tumors by number of observed high-risk features.26,35



AJCC 8 and BWH classification systems have been validated in studies conducted
at single-center academic institutions26,30,33 and in population-based
studies.16,29 In 2002, the American Joint Committee on Cancer defined the
objectives of cancer staging systems such that they should aim to classify
patients into groups that differ according to outcome (distinctiveness), have
similar outcome within each group (homogeneity), and worsening outcome with
increasing stage (monotonousness).1,19,29,36 Harrell's concordance index
(c-index or c-statistic) is often calculated and represents the probability
that a patient who will develop metastasis will be assigned a higher risk
score of this event by the model/staging system compared with a patient who
will remain event free. The c-index is equal to the area under the receiver
operating characteristic curve for binary outcomes in logistic regression
models.1,29 Additionally, the sensitivity and specificity of high tumor
classes (such as AJCC 8 T3/T4 and BWH T2b/T3) to predict poor outcomes, as
well as PPV and negative predictive value (NPV) are of importance in assessing
the prognostic value of each staging system.26



Ruiz et al26 compared the performance of AJCC 8 and BWH tumor classification
systems with respect to distinctiveness, homogeneity, monotonicity, and
c-statistic in a single-center academic cohort. The two classification systems
showed similar homogeneity (proportion of poor outcomes occurring in low tumor
classes) and monotonicity (proportion of poor outcomes occurring in high tumor
classes). High tumor classes AJCC8 T3/T4 and BWH T2b/T3 accounted for 18% and
9% of total cSCC cases, respectively, as well as 71% and 70% metastases, and
85% and 92% of deaths. AJCC8 T2 and T3 represented 23% of total cases, with
statistically indistinguishable outcomes.26 Sensitivity, Specificity, PPV, and
NPV of AJCC8 and BHW higher stages to detect NM/DSD were as follows:
Sensitivity: 0.73 vs 0.78, Specificity: 0.93 vs 0.85, PPV: 0.30 vs 0.17, NPV:
0.99 vs 0.99.26 C-statistic for LR demonstrated similar discriminative ability
by BWH and AJCC8 for LR with a BWH c-statistic of 0.86 (95% CI, 0.79-0.92) and
an AJCC8 c-statistic of 0.81 (95% CI, 0.73-0.88) (p = .09). BWH showed
superior discriminative ability for NM and DSD with a BWH c-statistic for NM
of 0.91 (95% confidence interval (CI), 0.85-0.96) vs an AJCC8 c-statistic of
0.84 (95% CI, 0.76-0.91) (p = .01). For DSD, the BWH c-statistic was 0.97 (95%
CI, 0.94-0.99) and the AJCC8 c-statistic was 0.91; (95% CI, 0.88-0.94) (p=
.005).26



AJCC8 and BWH stratification performance was recently evaluated in a
population-based nested case control study examining 887 metastatic cSCC cases
and 887 non-metastatic controls, factoring in the Salamanca T3 sub-
classification.29 The highest specificity was demonstrated for BWH, being
92.8% (95% (CI 90.8-94.3%), with a PPV of 13.2 (95% CI 10.6-16.2), NPV of 99.0
(95% CI 98.9-99.1) and c-index of 0.84 (95% CI 0.82-0.86). AJCC8 specificity
was 80.5 (95% CI 77.7-83.1), PPV was 6.8 (95% CI 6.0-7.7), NPV was 99.2 (95%
CI 99.2-99.3) and c-index was 0.78 (95% CI 0.76-0.80). The AJCC8 T3 Salamanca
refinement did not show any improvement in AJCC8 T3 cSCC staging, although the
number of T3 tumors was small with 37 eligible cases and 37 controls.29 Of
note, the odds ratio (OR) for metastasis for ACJJ8 T2 was 3.9 (95% CI 2.6-5.8)
and for T3, the OR was 11.6 (95% CI 8.3-16.0). The odds ratio for metastasis
of BWH T2a was 6.8 (95% CI 4.6-10.1) and for T2b it was 33.3 (95% CI
20.8-53.2), demonstrating significantly higher odds of metastasis with
increased stage.29 These data also suggest that AJCC8 tends to upstage low-
risk disease, whereas BWH is superior in identification of low risk
patients.37



**Surveillance and Treatment Intensity are Influenced by Risk-Stratification
Group**



The American Academy of Dermatology currently recommends tumor stratification
of localized cSCC using NCCN guidelines to provide practical clinical guidance
for management and follow up and demonstrates preference for BWH in terms of
the most accurate prognostication tool in localized cSCC.38 Current NCCN
management guidelines for local cSCC recommend MMS or other forms of
peripheral and deep en face margin assessment (PDEMA) for very high-risk
tumors, with consideration of adjuvant radiation therapy (RT) in cases with
poor prognostic features. Suggested follow up frequency and intensity vary
according to risk group. Patients with very high-risk cSCC that are recurrent
or have multiple risk factors that place them in the very high-risk group
warrant consideration of sentinel lymph node biopsy (SLNB) prior to PDEMA. At
this time, studies assessing the role of SLNB in cSCC have been heterogeneous
and small and while there may be prognostic value8,39-49 it is not evident
that SLNB with subsequent completion lymph node dissection or adjuvant
radiation therapy result in improved patient outcomes.8,40,42,44



A recent survey of 156 physicians aimed to assess how physicians across fields
of dermatology and other cancer specialists from head and neck
surgery/surgical oncology, radiation oncology, and medical oncology define
high-risk cSCC and approach patient management.27 Results revealed that most
dermatologists (89%) and other cancer specialists (93%) apply staging criteria
to cSCC, with dermatologists more often staging only high-risk tumors and
other cancer specialists preferring to stage all tumors. 71% of the surveyed
dermatologists used the BWH staging system along or in conjunction with AJCC8,
whereas 71% of other cancer specialists used only AJCC8. A contributing factor
to this preference is that BWH staging has been developed by dermatologists,
published in dermatology journals, and discussed at dermatology conferences.
There was consensus that AJCC T3 and BWH T2b or higher constitute a high
enough risk threshold to merit increased management intensity, including
radiologic imaging, SLNB, adjuvant radiation therapy, and increased follow up;
as such, they would also fall into the 'very high-risk' NCCN category. This is
aligned with Clinical Practice Guidelines from the American Society for
Radiation Oncology that provide a strong recommendation for postoperative
radiation therapy (PORT) in patients with T3 and T4 tumors and for patients
with desmoplastic or infiltrative tumors in the setting of chronic
immunosuppression.50 Of note, this survey did not query participating
physicians regarding use of NCCN guidelines for clinical management, although
it did assess risk perception of various clinicopathologic factors. The
recently added "very high- risk" category in NCCN guidelines represents an
effort at unification of management across staging systems and
clinicopathologic risk factors.27



**Predictive Biomarkers and Gene Expression Profiling**



Tumor biomarkers have been used to improve risk prognostication and clinical
decision-making in other cancer types51 and several are in development to
improve risk stratification of cSCC with the goal of bolstering the
information provided by the various staging systems. The AJCC8 and BWH staging
systems both stand to benefit from a stronger c-index and from improved PPV,
as lower PPV may lead to over-treatment and unduly intense follow up.51 Oh et
al15 constructed a nomogram using protein markers, Axin2 and p53, and clinical
variables such as tumor size, organ transplantation history, poor
differentiation, and invasion into subcutaneous fat to estimate individualized
risk for recurrence in a retrospective study with 145 cSCC patients, to reveal
a c-index of 0.809. Additional investigational biomarkers demonstrating
association with poor outcomes in patients with cSCC include PD-L1,52-55
inositol polyphosphate 5-phosphatase (INPP5a),56,57 p300,58 telomerase reverse
transcriptase (TERT) promoter mutations,59 CD133,60 long non-coding RNAs,61
and epidermal growth factor receptor (EGFR) overexpression.62,63 Further
studies are required to determine clinical validity and utility.



**DecisionDx-SCC (40-GEP)**



Castle Biosciences devised the DecisionDx-SCC (40-GEP) test which harnesses
changes in gene expression of 34 metastasis-associated genes and 6 control
genes to identify patients with high-risk of metastasis.35,64-66 The 40-GEP is
intended to be used in patients with localized, invasive and the presence of
one or more risk factors (i.e., high-risk) to guide treatment plans within
established management pathways. Risk factors that confer eligibility for
testing include: Tumors  2cm anywhere on the body, tumors located on head,
neck, hands, feet, pretibial, genitalia, tumors with poorly defined borders,
rapidly growing tumors, neurological symptoms in tumor region, tumor at site
of prior radiation therapy or chronic inflammation, immunosuppression,
perineural invasion of large or small caliber nerves, poorly differentiated
histology, deep invasion and aggressive histologic subtypes, aligning with
NCCN high-risk and very high-risk categories. The test is **not** intended to
be used in patients with localized low-risk cSCC, cSCC with the presence of
lymphovascular invasion; OR bone invasion; OR all four of the following risk
factors: diameter of at least 2 cm, AND poorly differentiated, AND perineural
invasion of at least 0.1 mm, AND invasion beyond the subcutaneous fat, cSCC
that has evidence of regional or distant metastasis, or on locally recurrent
cSCC. As a result, these criteria exclude patients who are in the NCCN low
risk category and many tumors that are staged as AJCC8 T1 and BWH T1. The
exclusion criteria also exclude tumors staged as BWH T3 and AJCC8 T4 (and
possibly some AJCC8 T3 tumors with minor bone invasion). However, it is
important to note that some patients (for example patients who are
immunosuppressed) may be classified as "high-risk" according to NCCN criteria
(making them eligible for 40-GEP testing) though they have a stage T1 tumor by
AJCC8 or BWH. In all, patients whose risk is either too low or too high to
benefit from the 40-GEP are excluded from testing. Thereby, the intended use
is focused on improving risk stratification within BWH T2a/2b and AJCC8 stages
T2/T3, allowing for testing of some T1 patients who have other 'high-risk'
factors.



The 40-GEP stratifies patients with one or more risk factors into a low
metastatic risk (Class 1), moderate metastatic risk (Class 2A) or high
metastatic risk (Class 2B) groups. The test was developed using a discovery
and development cohort consisting of 202 archival cSCC cases for gene
selection and further validated using archival tissue from a separate cohort
of 321 high-risk primary cSCC patients with known 3-year outcomes and an
overall metastatic rate of 16.2%.35 cSCC tissue and clinical data were
obtained from 23 independent centers and enrollment targeted patients with at
least one high-risk feature as defined by NCCN guidelines, or AJCC or BWH
stage greater than T1, either at the patient or tumor level.35 The 40-GEP
signature demonstrated statistically significant capability of stratifying
metastatic risk with different 3-year metastatic rates observed for patients
with Class 1 (n=203; 8.9%), Class 2A (n=93; 20.4%) and Class 2B (n=25; 60.0%)
results.35 The 40-GEP signature maintained predictive value when analyzed in
bivariable models with AJCC and BWH staging. Of note, AJCC and BWH also
maintained statistical significance in their respective bivariable models with
the 40-GEP. A multivariate Cox regression analysis was conducted for 295
patients with clinical features captured prior to definitive surgery including
male sex, tumor diameter assessed as a continuous variable per unit increase,
immune deficient status, location on head and neck and GEP Class 2A or 2B, to
reveal statistical significance for tumor diameter, head, and neck location,
as well as 40-GEP Class 2A or 2B (p<0.05). In a separate multivariate Cox
regression analysis with histopathological features captured after definitive
surgery for 321 cases, statistical significance was achieved for tumor
thickness >6mm, poor histological grade, invasion into fat, and a Class 2B
result. Of note, a Class 2A result was not statistically significant in this
model that included histopathological features only. Clarks Level IV/V and
perineural invasion were not significant predictors of metastasis on
univariate analysis and were not included in the multivariate model.35



It is important to note that 168 cases were missing clinicopathologic data
(mostly tumor thickness) and were staged with assumption of null values for
missing data which may have resulted in under-staging by BWH and AJCC,
inserting an element of bias.35 Post hoc sensitivity analyses showed
robustness of the primary bivariable analyses in spite of possible under-
staging. All specimens underwent central pathology review and restaging
according to contemporary staging criteria with medical records reviewed for
additional high-risk features. However, cases excised via Mohs had no tissue
available for review other than the shave biopsy, therefore there is
possibility for underreporting of high-stage features and resultant under-
staging.35 This is reflected in the higher percentage of metastasis occurring
in low T stages than previously reported in the literature and lower
sensitivities of AJCC and BWH staging than reported for other cohorts (39% and
25% vs 78% and 73%, respectively).26,35 Accuracy metrics for risk prediction
are found in Table 1 below, adapted from Wysong et al.35 The PPV of a Class 2B
result was 60%, whereas the PPV of any Class 2 result was similar to AJCC8 and
BWH high stage/low stage categories.



**Table 1. Accuracy of risk prediction of the 40-GEP and risk assessment
methods (n=321)**

Metric | 40-GEP (Class 2B vs 1/2A) | 40-GEP (Class 2 vs 1) | AJCC8 (T3/T4 vs
T1/T2) | BWH (T2b/T3 vs T1/T2a) | NCCN (high vs low)  
---|---|---|---|---|---  
Sensitivity, % | 28.8 | 65.4 | 38.5 | 25 | 96.2  
Specificity, % | 96.3 | 68.8 | 84.8 | 91.1 | 7.1  
PPV, % | 60 | 28.8 | 32.8 | 35.1 | 16.7  
NPV, % | 87.5 | 91.1 | 87.7 | 86.3 | 90.5  
  
     

Ibrahim et al subsequently reported on data from expansion of the previous
cohort to 420 patients with high-risk factors, 63 of whom developed regional
and/or distant metastases.65 The median time to metastasis was 0.9 years.65 Of
the 420 cases, 212 were classified as Class 1 with a metastatic rate of 6.6%,
185 were classified as Class 2A with a metastatic rate of 20.0%, and 23 were
classified as Class 2B with a metastatic risk of 52.2%. When stratified by
NCCN high-risk vs very high-risk criteria, Class 1 was associated with a 4.1%
metastatic rate in the high-risk cohort vs 11.9% in the very high-risk cohort;
Class 2 was associated with a 15.7% metastatic rate in the high-risk vs 25.3%
in the very high-risk cohort, and Class 2B was associated with a 37.5%
metastatic rate in the high-risk vs 60% in the very high-risk cohort. The
overall metastatic rate in the NCCN high-risk cohort was 9.8% vs 23.0% for the
very high-risk cohort.65 In multivariate Cox regression analysis with
clinicopathologic risk factors that included 40-GEP results along with poor
differentiation, perineural invasion, deep invasion, and tumor diameter, the
40-GEP was statistically significant along with poor differentiation and deep
invasion. 40-GEP results were also significant in bivariable analysis along
with either NCCN risk group, BWH, and AJCC 8 stage, which also remained
significant contributors to each respective bivariable model. Sensitivity of
the 40-GEP 2B vs 1/2A result was 19%, specificity 96.9%, PPV was 52.2% and NPV
was 87.2%, all of which are similar to that reported in Wysong et al.35,65



Arron et al64 evaluated a subset (n=278, 66%) of this cohort from patients
with cSCC of the head and neck with an overall metastatic rate of 19.4%. 126
of these patients had Class 1 results (metastatic rate: 8.7%), 134 had Class
2A results (metastatic rate: 24.6%), and 18 had Class 2B results (metastatic
rate: 55.6%). In this subset of patients, the PPV of a 40-GEP Class 2B result
was 55.6% compared to 37.0% for high stage AJCC8 and 40.0% for high stage BWH,
and the difference between the three was not statistically significant. As in
the larger cohort, the 40-GEP remained significant in bivariable analyses with
AJCC8 and BWH criteria, which were also significant contributors to each
respective model. In multivariate analysis with clinicopathologic risk
factors, the HR of Class 2A result was 2.28 (95% CI 1.08-4.81) and the HR of a
Class 2B result was 4.05 (95% CI 1.34-12.26). Clinicopathologic factors
significant along with 40-GEP results in a multivariate Cox regression
analysis included tumor diameter, poor differentiation, deep invasion, and
male sex.64 Sensitivity, specificity, PPV, and NPV of a 2B vs 1/2A result were
similar to that reported in Wysong et al and Ibrahim et al.35,65



The potential clinical utility of the 40-GEP lies in its incorporation into
existing risk-assessment frameworks in order to improve prognostic value and
facilitate individualized risk assessment, treatment, and follow up. Farberg
et al aimed to refine risk-directed patient management using the 40-GEP along
with NCCN guidelines and T stage criteria by examining 300 patients who met
NCCN high-risk criteria from the validation cohort presented in Wysong et
al.67 Of note, this work was performed prior to introduction of the NCCN very
high-risk category in 2021, and thereby only includes the former
categorization of "high-risk." As a result, this is not reflective of the most
up-to-date classification.



The proposed algorithm, which is not currently part of clinical guidelines,
starts with NCCN high-risk cSCC patients who subsequently undergo 40-GEP
testing and staging by BWH/AJCC8 with the following proposed management
strategy67:



**Table 2: Proposed Risk-Aligned Management Plans within the NCCN Guidelines
Framework**



(adapted from 67):

**Low intensity** | **Moderate intensity** | **High Intensity**  
---|---|---  
40-GEP Class 1 & BWH T1-T2a (8.1% metastatic rate) |

  * 40-GEP Class 1 & BWH T2b-T3 (18.8% metastatic rate)
  * 40-GEP Class 2A & BWH T1-T2a (17.8% metastatic rate)
  * 40-GEP Class 2A & BWH T2b-T3 (35.7% metastatic rate)

|

  * 40-GEP Class 2B & BWH T1-T2a (58.5% metastatic rate)
  * 40-GEP Class 2B & BWH T2b-T3 (71.4% metastatic rate)

  
**Management** | **Management** | **Management**  
Minimal clinical follow up every 6-12 months for 2 years, then annually |
Moderate clinical follow up every 3-6 months for 3-5 years, then annually |
Increased clinical follow up every 3 months for 2 years, then every 6 months
for 3 years, then annually  
Nodal assessment by palpation only | Nodal assessment by palpation with
consideration for imaging, nodal biopsy, and/or nodal dissection when
warranted | Nodal assessment by palpation with recommended imaging, nodal
biopsy, and/or neck dissection when warranted  
Avoidance of adjuvant radiation, chemotherapy, and immunotherapy |
Consideration of adjuvant radiation, chemotherapy and/or immunotherapy |
Recommendation of adjuvant radiation, chemotherapy, immunotherapy, and/or
clinical trials  
  
  

Current NCCN Guidelines have not incorporated use of the 40-GEP and recommend
follow up for high-risk patients to occur every 3-6 months for two years, then
6-12 months for 3 years, then annually for life. This includes complete skin
and regional lymph node exam and imaging can be considered if clinical exam is
insufficient for following the disease. Adjuvant radiation and systemic
therapy would not be recommended, unless the patient has positive post-
surgical margins and further surgery is not feasible.8 NCCN recommendations
for very high-risk patients include follow up every 3-6 months for 2 years,
then every 6 months for 3 years, then every 6-12 months for life, along with
imaging if clinical exam is insufficient for following disease. SNLB is
recommended for very high-risk patients who have multiple risk factors placing
them in the very high-risk group with a normal exam of the draining nodal
basin. Systemic therapy with or without radiation therapy is recommended in
cases of positive margins after MMS or other PDEMA, residual disease after
definitive therapy, and for non-surgical candidates. Adjuvant radiation
therapy is recommended for cases with positive-post surgical margins if
further surgery is not feasible and with negative margins in the setting of
extensive perineural, large, or named nerve involvement or other poor
prognostic features.8



Arron et al68 convened an expert panel of Mohs surgeons, surgical oncologists,
and radiation oncologists from academic medical centers and community
practices and discussed rationales and scenarios where the 40-GEP test result
may have clinical utility. The panel stated that the 40-GEP should not be used
as surrogate for standard of care treatment but as an additional data point
when determining individualized management plans for high-risk patients.68
Possible uses of the GEP are explored in relation to nodal evaluation,
adjuvant radiation therapy, and follow-up frequency as presented in Table 3
(adapted from 68).



**Table 3. GEP Test Results That May Impact Decisions on Follow-up and
Surveillance Intensity During the First Two Years after Diagnosis (Adapted
from Arron et al 68).**

**Decision Point** | **Staging** | **GEP Test Result**  
---|---|---  
Clinical follow-up | <20% metastatic risk | Class 1  
Clinical follow up + Nodal ultrasound/CT scan 1X/year |  20% to <50%
metastatic risk |

Class 2A

Class 2B  
  
Clinical follow up + Nodal ultrasound/CT scan 2X/year | >50% metastatic risk |
Class 2B  
  
  

To further illustrate potential clinical utility, Au et al69 described two
retrospective analyses of NCCN very high-risk cases, one with a Class 1 result
and the other with Class 2B result. Case 1 was a 65-year-old male with history
of renal and liver transplantation and a 1.3 cm poorly differentiated cSCC on
his left temple (BWH T2a and AJCC8 T1, NCCN very high-risk). He underwent MMS
with possible residual disease. The patient declined further treatment and was
disease free at 4 years. He was retrospectively found to have a 40-GEP Class 1
result. Patient 2 was a 69-year-old male with history of liver transplant and
1.5 cm poorly differentiated cSCC on his left temple (BWH T2a, AJCC8 T1, NCCN
very high-risk) with subsequent clearing following MMS. The patient developed
metastatic cSCC within three months of MMS and was retrospectively found to
have a 40-GEP Class 2B result. Au et al69 state that Case 1 highlighted a
biologically less aggressive tumor that did not recur despite incomplete
surgical clearance whereas Case 2 highlighted a more aggressive tumor in spite
of clear surgical margins with MMS. The authors state that adjuvant treatment
may have been appropriate for Case 2 earlier in the disease course.69



The potential clinical impact of the 40-GEP has been assessed through
presentation of clinical vignettes and clinician surveys at conferences
showing that clinicians would alter their decisions to perform a SLNB and
recommendations for adjuvant radiation therapy and chemotherapy/immunotherapy
given 40-GEP results.70,71 However, outcomes data from prospective studies
with documented specific changes in management are lacking at this time.



Saleeby et al72 report on preliminary results from the prospective Clinical
Utility and Health Outcomes Study (UTILISE), which aimed to demonstrate
patterns of test utilization, distribution of results across clinicopathologic
variables, and impact on clinician recommendations for management in Medicare-
eligible high-risk patients. The study was conducted at 5 clinical sites and
involved 11 unique clinicians (8 dermatologists and 3 dermatology-based
physician assistants). The study consisted of two sequential phases, the Lead-
in Phase and Clinical Utility Phase. During the Lead-in Phase, clinicians
recorded a treatment plan assessment before receiving 40-GEP results for at
least five patients. After completion of treatment plan assessment for five
patients, clinicians were able to enroll new patients into the clinical
utility phase. The Lead-in Phase included a second (post-test) treatment
assessment completed after 40-GEP results receipt.72



At time of publication, the Lead-in Phase consisted of 31 patients, with 81%
having two or more risk factors. 68% (n=21) received a Class 1 result, 25%
(n=~8) received a Class 2A result, and 6% (n=1-2) received a Class 2B result,
with a median follow up of 41.7 weeks. At time of analysis, one patient with a
Class 2A result experienced regional metastasis. The Clinical Utility Cohort
included 59 patients, 60.3% of whom had more than one risk factor. This cohort
was comprised of 88% Class 1 (n=52) results, and 12% Class 2A results. There
were no Class 2B results and no cases of metastasis with a median follow up of
22.5 weeks. The impact on clinician perception of metastatic risk is depicted
in Table 4 adapted from Saleeby et al and the impact of the 40-GEP on
intensity of management is depicted in Table 5.72 The majority of queried
clinicians reported reassurance in the management plan they developed prior to
use of the 40-GEP and 24% stated that they made changes based on GEP results.
The precise changes to management outside of the broad categories "low,
moderate, high intensity" management were not published. Clinical patient
outcomes are not available at time of publication, with the exception of the
one Class 2A patient who developed metastasis. Therefore, it is not possible
to ascertain the effect of the 40-GEP informed change in patient management on
patient outcomes at this time.



**Table 4. 40-GEP Impact on Clinician Perception of Metastatic Risk**



**Clinician Perception of Risk: What is the patient 's risk of developing
nodal or distant metastasis?**  
---  
**40-GEP Class 1** | **40-GEP Class 2A**  
**Pre-GEP** | **Post-GEP** | **N** | **% of Class 1** | **Pre-GEP** | **Post-
GEP** | **N** | **% of Class 2A**  
<5% | <5% | 37 | 72.5% | <5% | 10-30% | 3 | 42.8%  
5-10% | <5% | 12 | 23.5% | 5-10% | 5-10% | 2 | 28.6%  
5-10% | 5-10% | 1 | 2.0% | 5-10% | 10-30% | 2 | 28.6%  
10-30% | <5% | 1 | 2.0% |   |   |   |  
  


**Table 5. 40-GEP Impact on Intensity of Management**



**Intensity of Management: What is the overall management recommendation for
this patient?**  
---  
**40-GEP Class 1** | **40-GEP Class 2A**  
**Pre-GEP** | **Post-GEP** | **N** | **% of Class 1** | **Pre-GEP** | **Post-
GEP** | **N** | **% of Class 2A**  
Low | Low | 36 | 70.6% | Low | Low | 1 | 14.3%  
Low | Moderate | 1 | 2.0% | Low | Moderate | 3 | 42.8%  
Moderate | Low | 8 | 15.7% | Moderate | Moderate | 1 | 14.3%  
Moderate | Moderate | 6 | 11.8% | Moderate | High | 1 | 14.3%  
  |   |   |   | High | High | 1 | 14.3%  
  




Hooper et al73 reviewed 2455 samples submitted during the first year of
clinical testing (August 31, 202-August 31, 2021) and found that 68.8%
(n=1687) had a Class 1 result, 28.3% (n=696) had a Class 2A result, and 2.9%
(n=72) had a Class 2B result. The majority of Class 1 results were identified
in samples with 1-2 risk factors, confirmative of a low-risk of metastasis.
Class 2A and 2B results were more likely to be found in samples from patients
with a greater number of risk factors when compared with Class 1,
demonstrating consistency with the increased risk associated with Class 2A and
2B results.73

While the 40-GEP is capable of metastatic risk stratification, it is unclear
how GEP-results can be consistently or accurately interpreted in the context
of baseline clinicopathologic risk as part of a comprehensive risk assessment
to change patient management. Along these lines, the literature presented to
date suggests, but does not adopt, a consistent and recommended patient
management strategy with regard to follow-up frequency, nodal assessment, and
adjuvant therapy for Class 1, 2A, and 2B tumors according to which outcomes
could be measured. Most patients receive a Class 1 or 2A result while Class 2B
results are rare; therefore, it is important to clearly define the difference
in management of patients with a Class 1 vs 2A result and the net benefit. To-
date, this has not been done. It is also important to examine the impact of
changes in patient management as a result on the 40-GEP on clinical outcomes
from larger real-world trials (rather than anecdotal case reports), as
misclassification can cause patient harm. Finally, test performance has not
convincingly demonstrated superiority to currently available staging tools and
clinicopathologic factors in the intended use population. The main concerns
are further outlined below.

The Class 2B result is rare and occurs more often (though not exclusively) in
patients with two or more risk factors, who would already likely be classified
as higher risk by existing tools. The relative rarity of the Class 2B result
is depicted in the Ibrahim et al65 validation cohort of 420 patients wherein
only 23 patients received a Class 2B result (12 metastatic), 18 of whom had 2
or more risk factors. Interestingly, when cSCC cases are stratified by NCCN
criteria into high-risk and very high-risk populations, the metastatic rate
associated with a Class 2B result was 37.5% in the NCCN high-risk cohort vs
60.0% in the very high-risk cohort,65 perhaps reflective of the overall
difference in prevalence of metastasis in both cohorts and underscoring the
importance of additional clinicopathologic risk factors. In Hooper et al's
examination of 2455 clinical samples from a year of clinical testing with the
40-GEP, only 2.9% received a Class 2B result.73 The majority of Class 1
results were identified in samples with 1-2 risk factors, confirmative of a
low-risk of metastasis. Class 2A and 2B results were more likely to be found
in samples from patients with a greater number of risk factors when compared
with Class 1.73

In the most recent prospective Clinical Utility and Health Outcomes Study
(UTILISE) conducted in 90 Medicare-eligible patients evaluated prospectively,
73 received a Class 1 result and 17 received a Class 2 result (Class 2A +2B)
(of which 1-2 were class 2B), demonstrating that a class 2B result is indeed
very rare in the community setting.72 11 clinicians (8 board certified
dermatologists and 3 physician assistants) who participated in the study were
queried about their perception of risk, demonstrating mostly reassurance in
their current treatment plan with a Class 1 result and some increase in
perceived risk with a class 2A result.72 24% of these 11 clinicians reported
that they made management changes based on 40-GEP results. It would be prudent
to examine in greater detail the patients for whom the 40-GEP led to a change
in management, the specific change in management, and the subsequent impact on
outcomes when compared to the currently recommended approach provided by
Society Guidelines (such as NCCN).

Since a Class 2B result is rare, the clinical utility and PPV of a Class 2A
(which is more likely) or Class 2 result should be examined. In the 40-GEP
validation by Ibrahim et al,65 the PPV of any Class 2 result (Class 2A + 2B)
is 23.6%, compared with 33.9% of BWH T2b/T3 and 30.0% of AJCC8 (T3/T4). In a
cohort restricted to the head and neck, the PPV of any Class 2 result is
28.3%, compared with 37.0% for AJCC8 and 40.0% of BWH T2b/T3.64 Thus, the PPV
of any Class 2 result is comparable to that of existing staging criteria. In
bivariable models that include the 40-GEP along with either BWH or AJCC8
staging criteria, the HR of a Class 2A result is comparable to that of BWH T
stage T2b/T3 or AJCC8 T3/T4.65 The majority of patients tested with the 40-GEP
receive a Class 1 or 2A result, which is comparable in terms of predictive
value to existing staging criteria. It would be prudent to further explore the
patients with Class 2B results who were not identified as very high-risk
according to all available staging criteria and risk factor analysis, but for
whom a Class 2B result would enable them to benefit from more intense
management. This data is not available aside from a handful of clinical
anecdotes.

While it has been shown that clinicians are willing to adopt the 40-GEP and to
potentially act on the results,69-71 it is not clear what the recommended
management changes should be and there is no outcomes data to support changes
in management. Also, some de-escalations of care may not be warranted based on
the risk scores provided in patient clinical reports as the metastatic risk
associated with a Class 1 and Class 2A result depends on other
clinicopathological variables. For example, sample patient reports state that
the metastatic rate for patients with 1 risk factor is Class 1 (6.6%), Class
2A (20.0%), Class 2B (52.2%) and for patients with 2 or more risk factors, the
metastatic rate is: Class 1 (9.0%), Class 2A (25.0%), Class 2B (50.0%), based
on data from Ibrahim et al.65 Farberg et al,67 showed that individuals with
AJCC8 stage T3/T4 have a 16.7% rate of metastasis with a Class 1 result and
BWH T2b/T3 Stage has 18.8% risk of metastasis with a Class 1 result. A Class
2A result carries a 34.8% metastatic rate in patients with ACJJ8 stage T3/T4
and 35.7% in those with BWH stage T2b/T3. This variability in metastatic rate
with a Class 1 result as a function of other clinicopathologic factors
underscores their importance and makes de-escalation of management intensity
challenging based on 40-GEP results, highlighting the importance of the
complete clinical picture beyond the absolute number of risk factors presented
in patient reports. Farberg et al67 attempted to integrate GEP results within
the NCCN guidelines framework, along with BWH and/or AJCC8 staging, however
this was not clearly defined nor consistently implemented in clinical
practice, with a lack of outcomes data. Accordingly, it is concerning that in
the UTILISE study presented by Saleeby et al,72 the majority of clinicians had
a perception that a Class I result conferred <5% risk of metastasis (Table 4),
which is not congruent with the above data, especially given that most of the
patients in the UTILISE study had more than 1 risk factor. As a result, there
is a risk that some patients may be under-treated as a result of the 40-GEP.

In addition, the currently available published literature does not describe
test performance in a patient population with the exclusion criteria proposed
by the test manufacturer - namely excluding patients with cSCC with the
presence of lymphovascular invasion; OR bone invasion; OR all four of the
following risk factors: diameter of at least 2 cm, AND poorly differentiated,
AND perineural invasion of at least 0.1 mm, AND invasion beyond the
subcutaneous fat, cSCC that has evidence of regional or distant metastasis, or
on locally recurrent cSCC. While these features are rare, they are likely
responsible for a portion of the very high-risk cases and PPV and NPV vary
with prevalence of metastasis. Also, while the presented literature compares
the 40-GEP to BWH and AJCC8 staging on sensitivity, specificity, positive and
negative predictive value, it does not examine distinctiveness, homogeneity,
and monotonicity, and c-index of the 40-GEP to better assess its overall
performance.

There are several limitations of the multivariate analysis performed in Wysong
et al and Ibrahim et al.35,65 These include treatment of tumor diameter as a
continuous variable when it may not show a linear relationship with outcome.74
Tumor size greater than 2 cm but less than 4 cm is considered a high-risk
feature according to NCCN criteria and upstages tumors from T1 to T2 in AJCC8,
whereas tumors greater than 4 cm are considered very high-risk, and upstage
AJCC8 stage from T2 to T3.8,75 Also, perineural invasion was considered
positive in the analysis regardless of nerve caliber, whereas nerves measuring
0.1 mm or more are an NCCN very high-risk feature as are tumor cells within
the nerve sheath of a nerve lying deeper than the dermis.8 Additional risk
factors that characterize a patient as high-risk and eligible for testing with
the 40-GEP were not included in the model but may have clinical predictive
value. These include tumor location on the head, neck, hands, feet, pretibial,
and anogenital region, site of prior radiation therapy or chronic inflammatory
process, rapidly growing tumors, presence of neurologic symptoms, and
aggressive histologic features such as acantholytic/adenoid, adenosquamous, or
metaplastic tumors as well as desmoplasia, which although rare, is associated
with a 10-fold greater risk of local recurrence and a 6-fold increased risk of
metastasis compared to tumors without this feature.76 Additional
considerations include the clinical utility of this test for patients with
tumors with positive surgical margins after excision and in patients with
multiple tumors.77 Finally, there are differences in metastatic risk as a
function of surgical approach, such that it would be prudent to explore the
40-GEP's PPV for tumors treated with MMS vs WLE. A more complete analysis that
includes all of the high-risk factors that confer test eligibility would
provide greater clarity of the predictive capability of the 40-GEP along with
possible additive value. The significance of other clinicopathologic factors
along with 40-GEP in the multivariate model presented in Ibrahim et al65
underscores their collective importance and perhaps the 40-GEP may have
increased predictive value and offer a more personalized assessment of risk as
a nomogram.

In addition, local recurrence contributes significantly to disease-specific
death78-80 and the 40-GEP proposes changes in management and follow-up
frequency based on the risk of metastasis. It would be prudent to examine
performance of the 40-GEP with disease specific death as an endpoint aside
from metastasis-free survival to determine the overall impact on patient
outcomes. Finally, the clinical utility and test performance of the 40-GEP has
been reported in a population that is 73.3% male and 99.3% Caucasian,65 which
is representative of the majority of patients with cSCC. Nevertheless, this
represents a potential evidence gap, as representation of test performance
characteristics should be inclusive of and addressed in patients of color, who
have been shown to have a higher metastatic rate compared to Caucasians.81-84

The published literature to date does not outline a consistent and clear
management strategy for patients with Class 1, Class 2A, and Class 2B results
with respect to frequency of follow up, SNLB, and adjuvant therapy within the
existing framework of clinical guidelines and staging. While management
strategies have been proposed,67,68 it is imperative to clearly define changes
in patient management given 40-GEP results and to measure clinical outcomes
based on those changes. Ideally, there should be evidence of improved risk
stratification without detriment to patient outcomes. Patient
misclassification and under-treatment as a result of a false negative result
could cause significant harm and needs to be addressed.

In conclusion, although there is apparent need and clinical utility for
molecular markers to improve risk stratification of patients with cSCC, the
current evaluated tests at the time of drafting this policy have not yet
demonstrated definitive value above the combination of available clinical,
pathological, and staging criteria in accurate risk stratification. Therefore,
clinical validity and clinical utility have not yet been established for
molecular tests that offer risk stratification for cSCC. This contractor will
continue to monitor the evidence and may modify coverage based on new
information in the pertinent literature and society recommendations.