Photo by Taryn Elliott

A cancer diagnosis can feel like a storm, tossing families into a whirlwind of emotions and uncertainties. But amidst the choppy waters, there’s a glimmer of hope: remission. It’s a word that brings immense relief, a chance to rebuild and reclaim normalcy. Yet, for many families, remission comes with a new term – Minimal Residual Disease (MRD).

What is MRD?

MRD is like tiny boats still bobbing in the ocean after the storm has passed. These are a small number of cancer cells, too few to be detected by traditional tests like scans, that are still there post-treatment. To break it down further, “Minimal” denotes a tiny number of cells, typically defined as less than 1 in 10,000 to 1 in 10,000,000 healthy cells, depending on the cancer type and detection method. “Residual” refers to cancer cells remaining after initial treatment despite complete remission (no apparent disease by conventional methods). MRD detection and interpretation depend on the specific cancer, the type of test used, the treatment received, and individual patient factors. Pediatric cancers, while thankfully less common than adult cancers, often respond well to initial treatment. However, MRD detection adds a crucial layer of understanding. Even if a child appears cancer-free, the presence of MRD can significantly increase the risk of relapse, which is why detection is critical. It’s like finding a single enemy pirate sneaking through the supposedly liberated waters – a sign that the threat is not truly gone.

Which Cancers are Impacted?

While MRD testing is becoming increasingly important, its use varies across different cancers. Here’s a breakdown:

Blood Cancers: The main types of cancer where MRD testing is routinely used due to their presence in the bloodstream, making detection easier. Leukemia, lymphoma, and myeloma often show high rates of detectable MRD. For example, in acute lymphoblastic leukemia (ALL), over 90% of patients achieve MRD negativity after initial treatment, a positive sign!

Solid Tumors:  While research is ongoing, MRD testing for solid tumors like breast or lung cancer is still in its early stages. The challenge lies in developing sensitive enough tests and figuring out what level of MRD actually matters for these cancers.

Detecting MRD

Unlike traditional tests that look for bulk tumors, MRD detection relies on sophisticated techniques like:

• Flow cytometry: This technique uses fluorescent antibodies to target specific markers on the surface of cancer cells. The cells are then passed through a laser beam, and their fluorescence is measured. This allows researchers to count and characterize the cancer cells in a sample, such as bone marrow or blood.
• Polymerase chain reaction (PCR): This molecular technique amplifies specific DNA sequences associated with cancer cells. Even if only a handful of cancer cells are present, PCR can make their DNA detectable. Different types of PCR exist for MRD detection, such as:

• • Quantitative PCR (qPCR): Measures the exact number of cancer cells present.
  • Reverse transcription-quantitative PCR (RT-qPCR): Used for cancers of blood origin, where it detects and amplifies RNA specific to cancer cells.
  • Next-generation sequencing (NGS): This powerful technique can sequence the entire genome of cancer cells, allowing for the identification of genetic mutations specific to the cancer. NGS is particularly useful for identifying rare mutations in a small number of cancer cells. 

It’s important to note that MRD testing is still evolving, and new, more sensitive techniques are constantly being developed. The choice of which test to use should be made in consultation with a healthcare professional specializing in the specific type of cancer.

MRD is important for a child’s treatment plan

Knowing a child’s MRD status empowers doctors to make informed decisions about their care: 

• 

  Photo by Pavel Danilyuk

  Monitoring for relapse: Regular MRD testing acts as an early warning system, potentially catching relapses before they cause symptoms. This allows for quicker intervention and potentially better outcomes.
• Guiding treatment: Depending on the MRD results, doctors might adjust the treatment plan. For example, if MRD is still present after initial therapy, additional treatment might be recommended to eliminate those hidden enemies.
• Personalized care: MRD testing is a step towards personalized medicine, tailoring treatment to the specific cancer and its behavior in each child. This can lead to more effective therapies with fewer side effects.

Challenges and future directions:

While MRD testing is a powerful tool, it’s still evolving. Challenges include:

• Limited sensitivity: Some tests might miss very low levels of MRD.
• Standardization: Different labs and tests might produce varying results, making comparisons difficult.
• Solid tumors: Detecting MRD in solid tumors is trickier than in blood cancers. 

However, research is ongoing, and scientists are constantly improving MRD detection and interpretation. The future holds promise for even more personalized and effective cancer treatment for children. Remember, finding MRD doesn’t necessarily mean a child will relapse, and a negative test doesn’t guarantee a cure. It’s a complex picture, and open communication with your child’s doctor and healthcare team is critical. MRD is just one piece of the puzzle and doctors consider various factors when making treatment decisions.

Understanding MRD is a crucial step towards conquering childhood cancer. By equipping yourself with knowledge and you can give your child the best chance at a bright and healthy future. 

References and Additional Resources:

• The Leukemia & Lymphoma Society: https://www.lls.org/booklet/minimalmeasurable-residual-disease-mrd
• MD Anderson Cancer Center: https://www.mdanderson.org/cancerwise/what-is-minimal-residual-disease–mrd–multiple-myeloma-lymphoma-leukemia-patients.h00-159383523.html
• National Cancer Institute: https://www.cancer.gov/
• Cleveland Clinic: https://my.clevelandclinic.org/health/diagnostics/22086-flow-cytometry
• Cancer Support Community: https://www.cancersupportcommunity.org/measurable-residual-disease
• Enzo Life Sciences: https://www.enzolifesciences.com/science-center/technotes/2017/march/what-are-the-differences-between-pcr-rt-pcr-qpcr-and-rt-qpcr?/
• St. Jude: https://www.stjude.org/treatment/disease/solid-tumors/what-is-solid-tumor.html

Facing your child’s cancer journey can feel overwhelming. But you don’t have to go through it alone. Here to Serve is a national nonprofit that provides practical and emotional support to families like yours. From financial assistance to meal coordination and family updates, we are here to lift a weight off your shoulders so you can focus on what matters most – your child. Click here to connect with Here to Serve and learn how we can help.

About the Author: Sameera Rangwala, M.S., M.P.H.

With over 15 years of experience in the biotechnology industry and a passion for science education, Sameera Rangwala is a life science educator who actively engages with the cancer community through her informative blog posts and words of encouragement.

All content in this blog is for informational and educational purposes only. Always consult a medical provider in your particular area of need before making significant changes in your medical decisions or lifestyle.