A research team at Gangnam Severance Hospital has found that radiation therapy can significantly increase the effectiveness of chemotherapy for metastatic and recurrent colorectal cancer.

According to the hospital, the most effective treatment for metastatic colorectal cancer is targeted therapy and chemotherapy, which block only a specific gene with a mutation.

However, some patients show a mixed response, developing tolerance in only a few lesions during treatment. While it is common to change the anticancer drug in such cases, there is a limit as the changed drug may have lower efficacy than the original drug and reduce available drugs for the patient.

To provide a solution, the team, led by Professor Jang Ji-seok of the Radiation Oncology Department, conducted a study that showed that precision radiation therapy increases the effectiveness of chemotherapy in patients with small advanced colorectal cancer. Professors Koom Woong-sub and Byun Hwa-kyung at Severance Hospital participated in the study.

During the study, the research team compared and analyzed the maintenance period and survival rate of chemotherapy in 91 patients with small advanced metastatic colorectal cancer who received precision radiation therapy from 2011 to 2020, and the treatment data of 4,157 metastatic colorectal cancer patients who received systemic drug treatment at Yonsei Cancer Center.

The analysis confirmed that the minor progressive patient group who received precision radiation therapy maintained the existing drug treatment for an average of 9.5 months when the hospital suspected that tolerance had developed. Also, 31 patients of the patient group maintained the existing drug for more than one year.

The team stressed that considering that the average duration of chemotherapy for all metastatic colorectal cancer patients is an average of five months, the precision radiation therapy extended the period significantly.

The survival rate of the minor progressive patient group who received precision radiotherapy was also high.

“Until now, even if a large number of lesions respond to drug treatment, it was conventional to discontinue the existing drug treatment and proceed with the new drug treatment for metastatic colorectal cancer patients if a small number of lesions became resistant to the original drug treatment,” Professor Jang said. “If a small number of lesions causing problems are selectively treated with precision radiation therapy, hospitals can maintain the effect of drug treatment without increasing side effects, a new treatment option for metastatic colorectal cancer.”

However, hospitals should avoid its indiscriminate application as minor advanced metastatic cancer accounts for only a small portion of the total, and treatment decisions must be made considering various clinical situations, Jang added.

Clinical Colorectal Cancer has published the results of the research.