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Castle Biosciences Presents Data Demonstrating the DecisionDx-Melanoma Test Improved AJCC-Based Risk Prediction for Melanoma Recurrence and Metastasis

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Test demonstrated high technical reliability in over 17,000 clinical
orders

Castle Biosciences, Inc., the skin cancer diagnostics company providing
molecular diagnostics to improve cancer treatment decisions, today
announced the presentation of new data showing that the DecisionDx®-Melanoma
test improved risk prediction beyond that using American Joint Committee
on Cancer (AJCC) based staging. The study was presented at the DERM2018
NP/PA CME Conference held in Las Vegas, Nevada.

The study assessed the impact on risk assessment for patients with Stage
I-III melanoma when including results from the DecisionDx-Melanoma test
along with population-based AJCC staging in a 690-patient cohort. The
DecisionDx-Melanoma test uses tumor biology to provide an individual
risk assessment for patients with melanoma. Results from this analysis
showed that the addition of the test result to clinicopathologic AJCC
staging significantly improved risk stratification. Technical
reliability in over 17,000 clinical test orders was also assessed, and
showed 98.3% reporting success for samples with adequate tumor content.

Study Findings:

  • Multivariate analysis demonstrated that the Class 2B result was an
    independent predictor of melanoma-specific survival (MSS) with a
    greater hazard ratio than using AJCC staging alone to determine risk.
  • Results from this multicenter study in 690 patients with Stage I-III
    melanoma show that the addition of DecisionDx-Melanoma testing can
    significantly improve risk prediction based on AJCC 8th edition
    staging alone, and can better inform patient management
    decision-making.
  • Using AJCC staging alone, patients with Stage I melanoma have an
    estimated 98% MSS 5 years following diagnosis. However, patients in
    the Stage I melanoma group who had a Class 2B (highest risk)
    DecisionDx-Melanoma test result had an 89.5% 5-year survival, similar
    to risk estimates for Stage IIB disease.
  • For patients with Stage II melanoma, the DecisionDx-Melanoma test was
    able to further stratify patients from the AJCC-based 90% 5-year MSS
    into a low-risk (Class 1A) group with an MSS of greater than 99%
    (similar to Stage IA) and a Class 2B group with an MSS of 84.7%
    (similar to Stage IIB/C).
  • Using AJCC estimates alone, patients with Stage III melanoma have an
    MSS of 77% at 5 years. Use of the DecisionDx-Melanoma test enabled
    further stratification into a lower-risk Class 1A group with an MSS of
    94.8% (similar to low-risk Stage IIA) and higher-risk Class 2B group
    with an MSS of 61.2% (similar to Stage IIIC).

"Accurate risk assessment is important for clinical decision-making.
These results show that use of the DecisionDx-Melanoma test can further
inform clinicopathologic staging and help guide patient management
choices," said Federico A. Monzon, M.D., FCAP, Chief Medical Officer at
Castle Biosciences. "Incorporating DecisionDx-Melanoma test results can
drive improvements in follow-up and surveillance planning as well as
sentinel lymph node biopsy discussions."

Study Details:

  • Data from archival cutaneous melanoma tumor samples from 18 U.S.
    centers (n=690, Stage I-III) from previously reported cohorts were
    employed. Stage I-II cases were restaged according to AJCC 8th edition
    criteria. Importantly, the 5-year MSS rates for Stages I, II and III
    in this cohort were similar (within ±1%) to those reported for the
    AJCC 8th edition cohort.
  • Class 1A and 2B-predicted MSS outcomes for each stage were compared to
    5-year MSS rates associated with AJCC 8th edition stage groups.
    Patients were assigned a binary risk group, with Stage I-IIA
    considered low risk and Stage IIB-III high risk, based on National
    Comprehensive Cancer Network (NCCN) guidelines for surveillance and
    follow up.
  • Technical success was determined for 17,102 clinical
    DecisionDx-Melanoma orders received between July 2016 and April 2018,
    of which 96.3% had sufficient tumor content to perform the test. The
    DecisionDx-Melanoma test achieved a 98.3% technical success rate for
    samples with sufficient tumor content.

About DecisionDx-Melanoma

The DecisionDx-Melanoma test uses tumor biology to predict individual
risk of melanoma recurrence and sentinel lymph node positivity
independent of traditional factors. Using tissue from the primary
melanoma, the test measures the expression of 31 genes. The test has
been validated in three multi-center studies that have included 690
patients and have demonstrated consistent results. Performance has also
been confirmed in four prospective studies including 702 patients. The
consistent high performance and accuracy demonstrated in these studies,
which combined have included over 1,300 patients, provides confidence in
disease management plans that incorporate DecisionDx-Melanoma test
results.

Prediction of the likelihood of sentinel lymph node positivity has also
been validated in two prospective multicenter studies that included over
1,400 patients. Impact on patient management plans for one of every two
patients tested has been demonstrated in multi-center and single-center
studies. More information about the test and disease can be found at www.SkinMelanoma.com.

About Castle Biosciences

Castle Biosciences is a molecular diagnostics company dedicated to
helping patients and their physicians make the best possible decisions
about their treatment and follow up care based on the individual
molecular signature of their tumor. The Company currently offers tests
for patients with cutaneous melanoma (DecisionDx®-Melanoma,
DecisionDx®-CMSeq; www.SkinMelanoma.com)
and uveal melanoma (DecisionDx®-UM, DecisionDx®-PRAME
and DecisionDx®-UMSeq; www.MyUvealMelanoma.com),
with development programs in other underserved cancers. Castle
Biosciences is based in Friendswood, Texas (Houston), and has laboratory
operations in Phoenix, Arizona. More information can be found at www.CastleBiosciences.com.

DecisionDx-Melanoma, DecisionDx-CMSeq, DecisionDx-UM,
DecisionDx-PRAME and DecisionDx-UMSeq are the trademarks of
Castle Biosciences, Inc. Any other trademarks are the property of their
respective owners.

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