Next-Generation Sequencing (NGS) for Colon Cancer: Who Should Get Tested?

Next-generation sequencing (NGS) is a super advanced tool that has changed how we study genes. It’s like a modern toolbox used by scientists to quickly and affordably read the instructions of an organism’s DNA or RNA. This has helped researchers read a lot of genetic information fast, like reading a whole book, so they can understand entire sets of genes, find differences in genes, and study how genes work in a really big way.

NGS has various names, which can be a bit puzzling. NGS is the same as next-generation testing, comprehensive genomic profiling, broad molecular profiling or high-throughput sequencing. It is also commonly referred to as molecular testing.

NGS isn’t a particular test for a specific type of cancer. Instead, it’s a group of tests or technique that searches for all the genetic changes in a tumor’s genes. “Molecular testing is the process of analyzing the biological molecules such as DNA and RNA and other biological molecules,” Dr. Aman Opneja, Medical Oncologist at Duke Cancer Center Gastrointestinal Clinic and Duke Cancer Center Raleigh, told SurvivorNet. “We can use those testing results to gain insights into the cancer genetics, which can help us make some important treatment decisions and also help us in prognostication.”

What is DNA?

Imagine that DNA is like a recipe book for living things. Just like a recipe book contains instructions for cooking delicious meals, DNA contains instructions for building and running every living thing on Earth.

DNA stands for “deoxyribonucleic acid.” It’s a special code made up of four different “letters” A, T, C, and G:

  • Adenine (A),
  • Thymine (T)
  • Cytosine (C)
  • Guanine (G)

These letters are like the alphabet of life. They form long chains, just like sentences in a book. These chains are bundled up inside tiny structures called cells, which are like the kitchen of a living thing.

Every living creature, whether it’s a plant, an animal, or a person, has its own unique recipe book (DNA). This recipe book tells the cells how to do everything: from making your hair a certain color to helping your body fight off illnesses.

Reading DNA

Were you aware that your DNA can actually be read?

We recognize that DNA holds a treasure trove of details that shape our identities. However, in order to truly grasp this information, we must first learn the skill of reading it.

Genes are like different chapters within the DNA “book,” collectively serving as a set of instructions that direct our cells, much like the codes that guide a computer’s actions. For a long time, we lacked the means to decode these genetic instructions.

It wasn’t until the 1970s that a groundbreaking technology called DNA sequencing was invented, allowing us to read the DNA code. This breakthrough enabled scientists to interpret, comprehend, and compare genetic data, significantly advancing our understanding of biology.

Today, sequencing technologies are pivotal in various fields, ranging from healthcare to agriculture. Interestingly, DNA sequencing played a vital role during the COVID-19 pandemic, aiding us in analyzing the coronavirus and swiftly developing vaccines.

NGS and Cancer

Cancer has always been a puzzle for doctors because each type varies, and even the same kind can act differently in different people. The mistakes in DNA that cause cancer can be like unique clues, which DNA sequencing can uncover. Nowadays, scientists are using NGS to examine the special DNA code of each patient’s cancer and find these unique clues. This helps doctors make treatments that are just right for each person.

For instance, two patients with the same cancer might not respond the same way to a certain medicine. It might work for one but not for the other. NGS can spot tiny changes in their DNA codes, helping doctors understand how to create treatments tailored to each person’s unique genes. This special kind of treatment is called personalized medicine.

For patients fighting against cancer, the goal of NGS is to identify the exact mutations present in their tumor. The next step is to match these mutations with treatments that are already approved or under investigation in clinical trials.

The core idea is that by tailoring therapies to match particular genetic changes, it’s possible to improve both the survival rate and the overall well-being of certain cancer patients.

Who benefits the most?

Molecular testing can be performed for all colon cancer patients.

“Molecular profiling is an important testing for all stages of cancer. In early stage colon cancer, it can have more predictive value where it can help predict utility of chemotherapy for cancer patients,” adds Dr. Opneja.

“It can also help us identify genetic syndromes, which is … more important in our younger patients with colon cancer. In advanced stages of colon cancer, it can help us understand tumor biology and also help us select the best treatment option and look for clinical trials.”

How is NGS performed?

Dr. Opneja explains that the test can be conducted via the cancer tissue that’s obtained during biopsy or surgery.

“Another way to do the testing, is it can be done via blood, where the test can pick up the cancer DNA in the blood and analyze it for the gene changes,” adds Dr Opneja. This is known as Liquid Biopsy.

What is a liquid biopsy?

A liquid biopsy is a blood test that detects cancer cells or DNA that are circulating in the blood, called “circulating tumor DNA” or “ctDNA.” Similar to how normal cells in our body die and get replaced, cancer cells also go through this process. As these cancer cells die, they break apart and are set free from the tumor into the bloodstream.

“Circulating tumor DNA is the newer technology in which we can try to find the DNA of the cancer in the blood,”  adds Dr. Opneja.

A liquid biopsy finds tiny bits of DNA from cancer cells in the bloodstream. This kind of biopsy is not the same as other types, like when doctors take small pieces of tissue using needles to figure out what type of cancer someone has. With a needle biopsy, a doctor takes a small piece of a tumor, and a specialist looks at it under a microscope to check for cancer mutations.

But a liquid biopsy is easier; doctors just take a little bit of blood, like when you get a blood test. Then they send the blood to a lab to see if there are any cancer clues in it.

“If you go to a clinic and have your regular scans, it still takes a while for the cancer to show up on a scan. And sometimes there might be a small spot on a scan which may be indeterminate. The circulating tumor DNA can actually help pick up the DNA that’s the fragment of the cancer in the blood — and help us catch the cancer early, which can lead to more interventions. But those are in the clinical trials right now,” explains Dr. Opneja.

Questions to Ask Your Doctor

  • How aggressively should my cancer treatment be?
  • Am I eligible to receive targeted therapy? Am I more, or less, likely to respond to this treatment?
  • Do I have any genetic mutation that would change the course of my treatment?
  • How long does it take to get my NGS testing results?
  • Do you need both the tissue sample and blood samples for NGS testing?
  • Is there a clinical trial that would be relevant for me?

Learn more about SurvivorNet’s rigorous medical review process.

Dr. Rodrigo C. Leão Edelmuth is a board certified digestive surgeon at Hospital Israelita Albert Einstein in São Paulo, Brazil. He holds his General Surgery and Digestive Surgery degree from São Paulo University Medical School. He underwent a postgraduate course on Surgical Leadership at Harvard Medical School and he is also a visiting fellow in the Department of Surgery at Weill Cornell Medicine in New York.   Read More

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