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How Mohs surgeons utilize prognostic testing for high-risk cutaneous squamous cell carcinoma (SCC): a clinical impact study

› JJS, SJK, ALF, AP, BR are employees and shareholders of Castle Biosciences, Inc.
› STA is a consultant for Castle Biosciences, Inc.

Sarah T. Arron, MD, PhD1; Alison L. Fitzgerald, PhD2; Jennifer J. Siegel, PhD2; Anesh Prasai, PhD2; Briana Rackley, PhD2; Sarah J. Kurley, PhD2; Brent Moody, MD3
1Peninsula Dermatology, Burlingame, CA, USA; 2Castle Biosciences, Inc., Friendswood, TX, USA; 3Skin Cancer Surgery Center, Nashville, TN 

For more information: skurley@castlebiosciences.com

›97% of Mohs surgeons in this study are familiar with or use the 40-
GEP test for high-risk SCC patients.

›Study results determined that clinicopathologic risk factors most likely
to cause metastasis are also ones that would prompt usage of the
personalized molecular information provided by the 40-GEP.

›40-GEP results guide Mohs surgeons to make risk-aligned
management plans and increase their confidence in these decisions.

›Overall, the 40-GEP can focus treatment options in the most risk-
appropriate manner, allowing for an optimization of healthcare
resources and improved patient outcomes.

Conclusions
› An anonymous survey was distributed to current American College of Mohs Surgery

(ACMS) members. The study consisted of demographic questions, familiarity with and use
of NCCN guidelines, AJCC-8 staging, BWH staging, and the 40-GEP.

› Participants (n=39) were provided with background on the validation of the 40-GEP test,
then evaluated the use of risk factors for the assessment of SCC patients within their
practice and which were concerning enough to warrant the use of the 40-GEP.

› Participants were presented with a high-risk SCC patient vignette and asked for their risk
assessment and treatment approaches pre- and post-40-GEP results.

Presented at Fall Clinical Dermatology Conference, October 20-23, 2022, Las Vegas NV

Disclosures

› As Mohs surgeons are a clinical specialty likely to see high-risk SCC patients
frequently, a clinical impact study was performed to determine how patient
management decisions are impacted by their use of the 40-GEP test.

Figure 1. Performance of the 40-GEP to Stratify Patients by 
Risk of Regional or Distant Metastasis from SCC

Synopsis

Objective

Methods

Results

References

› Of the 1.8 million annually diagnosed SCC cases, more than 95% are cured by surgery;
however, an average of 5% progress to metastasis, with up to 2.1% dying from the disease.1-3

› A SCC patient’s likelihood for poor outcomes governs management decisions regarding a
multitude of treatment modalities.

› The 40-gene expression profile (40-GEP) test has been validated to stratify primary SCC
patients having one or more clinicopathologic risk factors into three biological risk groups
(Low = Class 1; Moderate = Class 2A; High = Class 2B) based on risk for regional, nodal, or
distant metastasis (Figure 1). 4,5

› Clinical validity studies have shown an improvement to risk stratification of high-risk SCC
patients when compared to staging systems. 4,5

› When 40-GEP test results are incorporated into a clinician’s initial risk assessment, clinical
utility studies have demonstrated the ability of the test to personalize patient management
plans in a risk-aligned manner. 5-9

› Demographics of the n=39 Mohs surgeons who participated in the study are shown in
Table 1. The distribution of study participants usage of National Comprehensive Cancer
Network (NCCN) guidelines and staging systems for risk assessment, along with their
familiarity with GEP testing for SCC are shown in Figure 2.

Results

Table 1. Demographics of study participants  

Little or no

Low

Somewhat

Confident

Very

Baseline

Class 1

Class 2A

Class 2BC
o

n
fid

e
n

ce
 le

ve
l

0%

20%

40%

60%

80%

100%

Follow-up

Baseline (Pre-GEP)
Class 1
Class 2A
Class 2B

C
lin

ic
ia

ns
 R

es
po

ns
e

5-12x per year3-4x per year1-2x per year

Follow-up

1-2x per year 3-4x per year 5-12x per year

C
lin

ic
ia

n
 r

e
sp

o
n

se

0%

20%

40%

60%

80%

100%

Adjuvant Radiation Therapy

Baseline(Pre-GEP)
Class 1
Class 2A
Class 2B

C
lin

ic
ia

ns
 R

es
po

ns
e

Recommen
d

Conside
r

Avoid

C
lin

ic
ia

n
 r

e
sp

o
n

se

Adjuvant Radiation Therapy

Avoid Consider Recommend

0%

20%

40%

60%

80%

100%

Nodal Imaging

Baseline(Pre-GEP)
Class 1
Class 2A
Class 2B

C
lin

ic
ia

ns
 R

es
po

ns
e

Recommen
d

Conside
r

Avoid

Nodal Imaging

Avoid Consider Recommend

C
lin

ic
ia

n
 r

e
sp

o
n

se

0%

20%

40%

60%

80%

100%

C
lin

ic
ia

ns
 R

es
po

ns
e

Class 1
Class 2A
Class 2B

Baseline
(Pre-GEP)

Low intensity Moderate intensity High intensity

Overall Management Intensity

C
lin

ic
ia

n
 r

e
sp

o
n

se

Low intensity Moderate intensity High intensity

Management intensity 

Figure 2. Summary of study participants preferred methods 
of risk assessment and familiarity with GEP 

Years in practice (%)

1-10 years 46

11-20 years 38

21-30 years 8

>30 years 8

Table 2. Utilization of the 40-GEP by study participants 
aligns with NCCN very and high-risk factors

* Indicates NCCN defined very high-risk factor

› Table 2 displays the highest-ranking risk factors (on a scale of 1-5) most likely to cause metastasis
as decided on by study participants. Factors that participants rank as most concerning are also
the factors they feel would most likely benefit from the prognostic information provided by the
40-GEP.

› Study participants were presented with a high-risk SCC patient vignette (Figure 3). Responses to
treatment modalities demonstrated increases in elevation of management when Class results
indicated an increased risk of metastasis.

› Overall confidence in decision making increased when integrating 40-GEP test results (Figure 4)

Institution (%)

Academic center 33

Multi-specialty group 25

Other private practice 36

Hospital based 5

other 0

Institution (%)

Academic center 33

Multi-specialty group 25

Other private practice 36

Hospital based 5

other 0

Following NCCN guidelines

Always

Often

Sometimes

Rarely

Never

Staging System used

AJCC8*

BWH**

Both

I assess patients with
risk factors only

Familiarity with GEP testing for SCC

Not familiar

Somewhat familiar

Very familiar

I have used a GEP test for SCC

Patient Vignette
› 68-year-old male
› 2.6 diameter lesion on

left temple
› Biopsy confirmed SCC
› Infiltrating subtype
› Poor differentiation

Figure 3. Risk aligned treatment decision are made when 40-GEP 
test results are integrated into patient management

Figure 4. Confidence in patient management decisions increased 
with use of 40-GEP * American Joint Committee on Cancer Staging Manual, 8th edition; **Brigham and Women’s Hospital staging system

1. Rogers et al. JAMA Derm. 2015 4. Wysong, et al. J Am Acad Dermatol. 2021 7. Litchman, et al. CMRO. 2020
2. skincancer.org, Skin Cancer Foundation 5. Ibrahim, et al. Future Oncol. 2021 8. Arron, et al. J Drugs Dermatol. 2022
3. Schmults et al. JAMA Derm 2013 6. Teplitz, et al. J Drugs Dermatol. 2019 9. Hooper, et al. Cancer Invest. 2022

Baseline (pre-GEP) Class 1 Class 2A Class 2B

42% of Mohs surgeons
reported increased confidence
in management decisions with
40-GEP testing

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