Blood test identifies cancer patients who need chemo and those who don’t

When reporting good news in cancer research, there is usually a caveat that the promising breakthrough will need another five to 10 years of trials to advance to a clinical setting.

Not this time.

A blood test identifying which patients with stage II colon cancer need chemotherapy and which do not will be available later this year.

And that’s just the beginning.

The researchers from the Walter and Eliza Hall Institute (WEHI) in Melbourne and the Johns Hopkins Kimmel Cancer Center in the US are already conducting three new randomized trials to determine the efficacy of the blood test in patients with colorectal and pancreatic cancer.

Future trials are planned for patients in other stages of colon cancer and patients with ovarian cancer.

Blood test identifies cancer patients who need chemo and those who don't

What is stage II colon cancer?

Stage II colon cancer has ” grown through the colon wall, but has not spread to the lymph nodes or other organs.”

Nearly 4,000 Australians are diagnosed with it every year.

According to WEHI, “Most patients with stage II colon cancer are cured after surgery to remove cancer from the colon; cancer will recur in about 20 percent of patients.”

Standard practice is to offer chemotherapy to all patients with stage II colon cancer “despite the majority not needing it”.

The blood test changes all that.

The researchers say, “it could save thousands of colon cancer patients unnecessary chemotherapy.”

The trial also has the potential to accelerate the development of promising new treatment options.

What is the test?

After colon cancer surgery, the goal of giving chemotherapy to a patient is to kill small cancer cells that have traveled from the gut through the bloodstream to infect another organ, such as the liver.

Initially, these cancer cells, the so-called micrometastases, are too small to be identified by scans in the early stages of the tumor.

Eventually, these “invisible” cancer cells will grow large enough to be identified in a CT scan. But your doctor doesn’t want it to get that far.

Therefore, the patient undergoes chemotherapy in case these micrometastases are involved.

As these cells circulate, they release what is known as circulating tumor DNA (ctDNA) into the bloodstream — genetic material secreted by tumors.

The new blood test works by detecting ctDNA, which indicates that the cancer is spreading, helping researchers (and oncologists) determine which patients should receive chemotherapy.

The researchers found that when a patient’s blood test does not reveal ctDNA after colon surgery, “the risk of micrometastases is very low, and chemotherapy can be avoided because there are no more tumor fragments to kill.”

Associate Professor Jeanne Tie, a clinical scientist at WEHI and a medical oncologist at the Peter MacCallum Cancer Center, said:

“Our trial has convincingly demonstrated how the ctDNA blood test can be used to direct postoperative therapy in stage II colon cancer and significantly reduce the number of patients treated with chemotherapy without influencing the risk of cancer relapse.”

She said the ctDNA blood test could save about 600 Australians and more than 100,000 people worldwide “from unnecessary yearly chemo treatments”.

More than 450 patients and more than 20 hospitals across Australia were involved in the world’s first clinical trial, which started in 2015.

The research is published in The New England Journal of Medicine.

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