Gwen Nichols

MD, Chief Medical Officer of the Leukemia & Lymphoma Society

“We need consistent [MRD] tests, reproducible tests, and ones that the regulators will be able to look at and feel confident that the test is done properly so that the results are really meaningful.”

A peer exchange roundtable discussion about the sensitivity and reproducibility of MRD testing methods.

The amount of disease that is measurable depends on the testing method chosen.1-4 Important criteria to consider include assay sensitivity, specificity, and standardization, as well as patient impact.3

SENSITIVITY5-7:

the ability to detect residual disease even at low levels

  • This is usually expressed as a ratio of cancer cells detected among the cells in a sample (eg, 1 cancer cell in 1,000 or 10,000 total cells assessed)
  • Patients who are MRD negative at deeper levels of sensitivity have been shown to have improved clinical outcomes

SPECIFICITY8:

the ability of a test to report accurate and reliable results and to minimize false determinations

  • An assay must accurately differentiate between healthy and malignant cells
  • An assay should be robust enough to detect changes in cancer cell markers that can occur as a result of newer treatments such as antibody-targeted therapy

STANDARDIZATION9:

the reproducibility of assay results, regardless of the timing, location, or operator of the testing method

  • Assay standardization is critical when test results may be used to inform clinical decisions
  • Standardization can be assessed in a variety of ways. Regulatory pathways such as FDA clearance and CLIA certification provide verification of whether assays have been standardized

PATIENT IMPACT11:

the physical and financial experience patients can expect from testing

  • One important consideration is the amount and type of specimen needed for testing, as well as the criteria for sample quality and how easy or difficult the required sample may be to obtain
  • Testing costs and insurance coverage also are important, as is the availability of patient support
  • Tests should provide clear results that can be shared with patients to guide discussions
Therapeutic
advances
MRD
technology
1980
Bone marrow transplant
Targeted therapies
Immuno-oncology agents
CAR-T therapies
2020

Microscopy18,19

As the earliest approach to quantitative disease burden assessment, this technique enabled pathologists to visually evaluate and count cells using a microscope.

  • Cellular assessment with limited sensitivity that can range from 1 cancer cell in 20 cells assessed to 1 cancer cell in 100 cells assessed
  • Still utilized as an upfront diagnostic tool, but less commonly used post treatment due to limitations in sensitivity and precision
  • May not detect subclinical disease burden, which is known to be predictive of recurrence even in the absence of symptoms

Flow Cytometry1,5,16,18,19-23

New in the 1980s, this cellular assessment looks at cell-surface markers that can change throughout the course of disease.

  • Cellular assessment with modest sensitivity that, by conventional flow, can range from 5 cancer cells in 1,000 assessed to 1 cancer cell in 10,000 assessed, when 1,000,000 cells are tested; sensitivity levels with next-generation flow can range from 1 cancer cell in 10,000 assessed to 1 cancer cell in 100,000 assessed, when 1,000,000 cells are tested
  • Relatively rapid results (from 1 day)
  • Historically difficult to standardize, but recent efforts have been made to improve standardization
  • Fresh samples required
  • Results may be confounded by current immunotherapies that can alter expression of antigens

ASO-PCR18-20,24-26

Also developed in the 1980s, this molecular assessment method identifies and counts gene rearrangements using patient-specific primers.

  • Molecular assessment with high sensitivity that can range from 5 cancer cells in 100,000 cells assessed to 1 cancer cell in 1,000,000 assessed, when 1,000,000 cells are tested
  • Time-consuming (turnaround is typically 4 to 5 weeks)
  • Difficult to standardize due to being patient specific
  • Samples can be fresh or stored

Next-Generation Sequencing (NGS) MRD1,5,18,19,27-29

A molecular assessment method that began in the late 1990s, NGS can identify and count specific malignant cells.

  • Molecular assessment with high sensitivity of 1 cancer cell in 1,000,000 cells assessed, when 1,000,000 cells are tested
  • Relatively quick turnaround (typically 1 week)
  • Easily reproduced within and between patients (standardized)
  • Samples can be fresh or stored
  • Limited in-hospital availability, but available commercially as a send-out test

Prominent physicians emphasize the importance of MRD testing and its evolving role in hematologic cancer treatment, from prognosis to clinical decision-making.

In selecting an MRD assay, consider factors such as sensitivity, specificity, standardization, sample input volume, and turnaround time.3

References:
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