Clearing the way to better outcomes

A New Assay. A Better Answer for Brain Metastases.

CNSide is a recent advancement in cancer diagnostic testing that answers critical questions about brain metastases not reliably addressed by current technology:

Is There Tumor?

The CNSide assay detects and quantifies tumor cells in cerebrospinal fluid in patients with carcinomas with suspected brain metastases.

Is There Treatment?

The CNSide assay can identify actionable targets for treatment.

Is There Trend?

The CNSide assay can monitor tumor cell count, response to therapy, and disease progression.


Learn how the innovative CNSide assay is helping patients in these clinical webinars.

The CNSide assay provides significant advancement over CSF cytology and imaging for diagnosing and monitoring brain metastases.

The CNSide assay is a novel combination of cell-based and cell-free assays utilizing proprietary technology.

  • The CNSide assay is quantitative, while cytology and imaging are qualitative
  • The CNSide assay is more sensitive and can detect a higher percentage of tumor cells than cytology1
  • The CNSide assay detected tumor cells in approximately 80% of cases with suspected disease in one study compared with approximately 50% of cases examined by CSF cytology1

When you need an answer to your questions involving brain metastases, there is no substitute for the CNSide assay.

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Case Study

Brain Metastases Requires Real-World Answers

To meet the challenge of diagnosing and treating brain metastases, the CNSide assay can determine the answers to the following questions:

  • Is there tumor?

  • Is there treatment?

  • Is there trend?

  • 41-year-old female patient with a history of breast cancer presented with neurological symptoms—headache, double vision, and seizures
  • Imaging suggested signs of brain metastases
  • CSF cytology was indeterminate
  • Oncologist ordered the CNSide assay
CNSide Assay Results
  • >25,000 CSF tumor cells detected
  • Biomarker analysis positive for HER2
Decision Impact
  • Patient started on intrathecal trastuzumab
  • Repeated testing demonstrated a significant and sustained decrease in CSF tumor cell count

Approximately 50% of brain metastases have actionable mutations not detected in the primary tumor2


The CNSide assay provided identification of CSF tumor cells indicating brain metastases while an actionable biomarker gave the physician and patient confidence in the next step. The tumor responded to treatment and the patient resumed an active life.

CNSide Answered the Questions of Brain Metastases:

Is there tumor? YES

Is there treatment? YES

Is there trend? YES

Now there’s a better way to know.


For the information you need to diagnose and treat brain metastases, trust the insight that only comes from CNSide.

When to Use CNSide

To detect, count, and characterize tumor cells in cerebrospinal fluid (CSF). CNSide supplements current clinical methods of evaluation for the diagnosis and treatment monitoring of patients with suspected metastatic tumor involving the central nervous system.

Why Use CNSide

To confirm tumor involvement in the CSF, find actionable biomarkers and monitor treatment response.

How to Use CNSide

Send 8 mL of cerebrospinal fluid to Biocept.

CNSide Collection Tube Specifications

  • Tube Volume: 8.0 mL nominal liquid capacity
  • Tube Type: Plastic
  • Shelf Life: 18 months
  • Storage Temperature: 18°C – 25°C
  • Shipping Temperature: 15°C – 30°C
  • Specimen Stability: CSF-TCs: Up to 4 days

CNSide Collection Tube Specifications

The CNSide assay is not an FDA cleared or approved assay. It is a Biocept lab developed test and its performance characteristics were determined in Biocept’s CLIA-certified, CAP-accredited laboratory.


  1. Berz et al, Poster, IASLC, 2020
  2. Suh JH, Kotecha R et al., Nat Rev Clin Oncol 2020.