How DNA Sequencing Is Keeping Cancer Patients Alive Longer

By Temma Ehrenfeld @temmaehrenfeld
August 22, 2023
How DNA Sequencing Is Keeping Cancer Patients Alive Longer

Doctors have more information and more choices to fight even fast-growing cancers. Here's what you should know about DNA sequencing to prevent and treat cancer.

Personalized therapy has become the cornerstone of cancer medicine, with many examples of big improvements in diagnosis and therapy.

But more dramatic advances are on the way, as doctors translate information from multiple sources into individual treatment plans, perhaps even using computer algorithms in daily practice.


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Sequencing your genome — your overall DNA — can tell your doctors something about your likelihood of developing a particular kind of cancer.

Science is already helping women with breast cancer. Women who know that certain genes run in their family — and see those genes in tests — should go earlier and more frequently for mammograms. They are generally advised to treat their cancer more aggressively when possible cancer cells show up.

Four well-known risk scoring systems can help women with breast cancer determine choices about chemotherapy and radiation. Such tests and system may be on the horizon for more cancers.

It is also often possible to sequence the genes in a particular tumor, which may give a cancer treatment team essential information.

“It’s a very simple principle,” said Razelle Kurzrock, MD, an oncologist based in Milwaukee, Wis. “You pick the right drugs for each patient based on the tumor profile, not based on a part of the body or based on what type of cancer 100 other people have. It’s all about that patient sitting in front of me.”

As science advances, doctors will have a better understanding of another body system, the code that responds to the world, making genes active or turning them off. That is the science of epigenetics.

For example, oncologists now have a good idea of how genes and events that trigger epigenetic changes may progress step by step to colon cancers. That understanding has led to predictive biomarkers, most notably RAS mutations and new medicine that targets and may neutralize related proteins.

Many tumors evade the immune system’s attempts to stop them. It is essential to know why.

Doctors are also testing important immune cells from individual patients to find the cells most likely to recognize and neutralize a tumor’s genetic defects. The next step is reproduce the winning cells and give the patient a boosted dose of them.

The available tools have multiplied quickly. The Genetic Testing Registry, a branch of the National Institutes of Health, records tests for nearly 19,000 genes relevant to nearly 11,000 illnesses. The total number of tests that have contributed data to the registry is almost 78,000. After growing fast, the numbers have been fairly constant since 2019.

Some cancer centers are using artificial intelligence to analyze the best targets for therapy and options.

In the meantime, newer treatments are keeping some patients alive longer, although not saving them. In a study led by Kurzrock, about half of patients who were closely matched to drugs based on an analysis of their tumors survived for three years, compared to 25 percent who didn’t get the personalized approach.

In an analysis of drugs approved by the U.S. Food and Drug Administration for specific cancers, scientists found similar results. About half the time, the patients died within three years. It was common, however, for the cancer not to progress for about two years.

A great deal depends on what kind of cancer you have, the stage at which it is caught, and whether tell-tale variants show up on your tests.

Skin cancer

DNA sequencing tests have been especially useful for patients with late-stage melanoma, a deadly form of skin cancer that spreads quickly.

As recently as 2000, half of Stage IV patients died within about seven months after diagnosis. Now, among patients treated with two of the newest drugs, half live longer than six years, says Jedd Wolchok, MD, an oncologist at Memorial Sloan Kettering Cancer Center in New York.

About half of patients with a metastatic skin cancer have a mutation called BRAF V600E, which studies suggest may make their cancer spread faster. Even among those patients, the five-year survival rate is now 60 percent.

To improve on that number, scientists are investigating how the gene works, the epigenetic triggers for disease, and the effects of the various drugs available for BRAF-positive patients.

Lung cancer

AI is already playing a role in treating lung cancer, the most common cancer around the world and kills the most people. Estimates suggest, however, that scientists have identified fewer than half of the genes that drive non-small-cell lung cancer (NSCLC), which accounts for about 85 percent of all lung cancers. Without treatment, half of patients with advanced NSCLC live only six months.

A small number of NSCLC tumors, often found in patients who were never smokers, can be linked to an aberration in the epidermal growth factor receptor. Five drugs target that gene and generally are more effective than other kinds of chemotherapy, which can extend survival for only months. Those drugs can control the cancer for months or years, but not forever.

In a test of a drug called erlotinib, the median survival rate was nearly 29 months, meaning half of the people died before then and half lived longer.

For lung cancer patients, it’s still not possible for your doctors to answer the question, “How long do I have?” Some patients beat the odds and live for years, others do not.

As personalized cancer medicine advances, any extra time may give you another chance at treatment.  


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August 22, 2023

Reviewed By:  

Christopher Nystuen, MD, MBA and Janet O'Dell, RN