Gene test allows some colon cancer patients to safely skip chemotherapy

By Dennis Thompson
HealthDay Reporter

TUESDAY, June 7, 2022 (HealthDay News) — A blood test could save some colon cancer patients from unnecessary chemotherapy after surgery while ensuring those who would benefit from the treatment get it, researchers report.

The circulating tumor DNA (ctDNA) test looks for tiny amounts of genetic material released by cancer tumors, said co-investigator Dr. Anne Marie Lennon, director of gastroenterology and hepatology at Johns Hopkins University School of Medicine, in Baltimore.

The presence of cancer DNA in the blood is a sign that someone likely needs follow-up chemotherapy, Lennon said.

The test nearly halved the number of people with stage 2 colon cancer who received follow-up chemotherapy after surgery — 15% versus 28% for a control group who received standard cancer care, the researchers found.

At the same time, both groups had essentially the same chance of 2-year recurrence-free survival, 93% for the blood test group and 92% for the group receiving regular care.

“The bottom line is that there was no difference. This is the first study of its kind using ctDNA to guide patients’ therapy,” Lennon said. “This is the first study to show that you can use circulating tumor DNA to truly personalize cancer care.”

According to the American Society of Clinical Oncology, about 151,000 new cases of colon cancer are expected to be diagnosed in the United States by 2022. An estimated 52,580 deaths will follow.

For this clinical trial, researchers recruited 455 patients with operable stage 2 colon cancer in Australia and New Zealand. In stage 2, colon cancer has passed through the lining of the gut, but hasn’t spread to the lymph nodes, Lennon said.

It’s known that about 80% of patients with stage 2 colon cancer will only be cured by surgical removal of their tumor, while 20% will let the cancer come back unless they get follow-up chemo, Lennon said.

In the study, two-thirds of the patients were randomly assigned to have the ctDNA blood test, about four weeks after undergoing surgery. The rest had assessed their need for follow-up chemotherapy in the current fashion, passing judgment after viewing the removed cancer and assessing how it had spread in the colon.

Patients with a positive ctDNA result who underwent chemotherapy after surgery had a three-year recurrence-free survival of 86%, according to the researchers.

The researchers presented this study Saturday at the American Society of Clinical Oncology (ASCO) annual meeting, held in Chicago. The results of the clinical trial were also published in theNew England Journal of Medicine.

This study is likely to change the way stage 2 colon cancer is treated, said ASCO Chief Medical Officer Dr. Julie Graylow.

“If I were a patient, I would definitely want to know what my ctDNA showed,” Gralow said. “And I think this is really pretty solid data, so I think it has a great chance of influencing the standard of care in the US”

The test would spare many people the debilitating effects of chemo, including nausea, vomiting, fatigue and possible nerve damage, Lennon noted.

At the same time, it would increase the chances of high-risk people getting chemo even if doctors would otherwise be hesitant to let them have it.

“Often there is a reluctance to give older people chemotherapy,” Lennon said. “We’ll be able to say, look, if you’re ctDNA positive, we know that your risk of recurrence is very high. Even if you’re older, you have to take the chemotherapy.”

Gralow and Lennon added that this is a trial that could be immediately implemented for patients with colon cancer anywhere in the United States.

While only major cancer centers can perform such a blood test in-house, there are specialized labs to which the blood can be sent for the same analysis, the researchers added.

“They’re doing high volume and doing extremely well, and their cost has come down dramatically,” Lennon said. “It’s something everyone should have access to.”

The next steps will be to take the ctDNA test and see if it can be applied to later stages of colon cancer, as well as other cancers, to help assess who might benefit from chemotherapy, Lennon said.

More information

The US National Cancer Institute has more about colon cancer.

SOURCES: Anne Marie Lennon, MD, PhD, director, gastroenterology and hepatology, Johns Hopkins University School of Medicine, Baltimore; Julie Gralow, MD, medical director, American Society of Clinical Oncology; New England Journal of MedicineJune 4, 2022

Leave a Comment