MONDAY, June 3, 2024 (HealthDay News) -- There's potential good news for a sizable minority of people battling advanced colon cancer.

Doctors in Britain say that an immunotherapy drug, given before surgery, can help many more patients with a specific genetic profile stay cancer-free long term.

The finding pertains to people with stage 2 or 3 colon tumors with a genetic profile known as MMR deficient/MSI-High.

About 10% to 15% of colon cancers have this profile, said a team led by Dr Kai-Keen Shiu, of the University College London (UCL) Cancer Institute.

Giving patients with advanced MMR deficient/MSI-High colon cancers the immunotherapy drug pembrolizumab (Keytruda) before their surgery kept up to 10 times as many of them cancer-free, compared to if they had not received the drug, the trial found.

“We need to wait to see whether the patients in our trial remain cancer-free over a longer period of time, but initial indications are extremely positive," Shiu said in a university news release. He is a medical oncologist at University College London Health.

The findings were presented Sunday at the annual meeting of the American Society of Clinical Oncology in Chicago. The research was funded by Merck Sharp and Dohme, which make Keytruda.

As Shui's team explained, colon cancer caught early has a relatively good prognosis. But five-year survival falls to 65% for folks whose cancer is already at stage 3, and to just 10% for those with stage 4 disease.

Immunotherapies such as Keytruda have worked against many other types of advanced cancers, so the British group tried the therapy in 32 patients with stage 2 or 3 MMR deficient/MSI-High colon cancers.

Patients received nine weeks of Keytruda prior to surgery that aimed at removing the colon tumor.

The result: More than half of patients pre-treated with Keytruda showed no signs of cancer following their surgery, the researchers reported.

Compare that to prior studies, where just 4% of patients were found to be cancer-free after getting chemotherapy alone before their procedures.

"The median cancer-free period was 9.7 months and ranged from 5.3 to 19 months among individual patients," according to the UCL news release.

“Our results indicate that pembrolizumab is a safe and highly effective treatment to improve outcomes in patients with high-risk bowel [colon] cancers, increasing the chances of curing the disease at an early stage," Shui concluded.

Longer-term follow-up is planned, to see if the benefit lasts over the longer term, the authors said.

“This is a really very exciting new treatment for the 10-15% of patients who have the right genetic makeup. Immunotherapy prior to surgery could well become a ‘game-changer’ for these patients with this type of cancer," added Dr. Mark Saunders, a clinical oncologist at The Christie NHS Foundation Trust in Manchester, U.K.

"Not only is the outcome better, but it saves patients from having more conventional chemotherapy, which often has more side effects," Saunders said.

More information

Find out more about colon cancer at the American Cancer Society.

SOURCE: University College London, news release, June 2, 2024