For decades, doctors have removed people’s colorectal tumors and decided whether their patients needed subsequent chemotherapy by considering several risk factors.
This method was imprecise, and sometimes people who didn’t need chemotherapy got it anyway.
There is now a potential path forward.
New genetic sequencing technology can detect previously undetectable levels of cancer from just a blood draw. If a patient doesn’t have any circulating cancer DNA, they may not need chemo post-surgery, suggested recent research from Australia.
“What we knew is that a lot of those patients were cured with surgery alone. We just didn’t have a way to know which ones had microscopic cancer left in the blood, who needed chemo and who did not,” said Dr. Mohamedtaki Tejani, medical oncologist and director of the Gastrointestinal Oncology program at the AdventHealth Cancer Institute and the AdventHealth Research Institute.
Colorectal cancer is the fourth most common cancer in the United States.
Often, people underwent unnecessary chemotherapy – which uses powerful chemicals to kill cancer cells and costs thousands of dollars even with insurance – after their cancer was completely gone.
During chemotherapy, normal, healthy cells are often killed by the treatment, too, and though they can bounce back, their absence causes symptoms like nausea and vomiting, hair loss, exhaustion and fever.
Infertility, lung disease, other cancers, heart problems, hearing loss, nerve damage, memory issues or early menopause can all pop up years after the treatment ends, according to Mayo Clinic.
Tejani is leading the AdventHealth site of two National Cancer Institute clinical trials of this sequencing technology, named SIGNATERA, developed by the DNA-testing company Natera.
One clinical trial involves patients with stage 3 colon cancer, which is when the disease has spread to surrounding tissue or lymph nodes.
These patients are traditionally prescribed chemotherapy after surgery, even though around 50% of stage 3 colon cancer patients are cured by surgery alone, some estimates say.
The study will randomly give or withhold chemotherapy to stage 3 patients who have tested negative for circulating tumor DNA, then track their outcomes long term, Tejani said.
It began in March 2022 and will conclude around March 2030.
Another clinical trial of stage 2A colon cancer patients has been going on since 2019 and aims to finish up in 2027.
Some researchers have reservations, however.
In a study of Canadian medical professionals released in May, they called this technology’s potential applications a “holy grail” for detecting hereditary cancers. But they also worried about the impact of false-negative tests.
These could motivate patients to delay regular screenings, one medical professional feared.
In the future, Tejani hopes this test can also be used to screen for signs of colon cancer in those who haven’t yet been diagnosed, and for it to extend beyond colon cancer to improve care for other cancers, such as gynecologic or pancreatic cancers.
“I think there’ll be a day where all of us will be tested, and we’ll be able to see whether we’re predisposed in our life to have any particular cancer,” Tejani said.
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