A new test might allow some women with an aggressive form of breast cancer to skip chemotherapy without harm, researchers say.
Women with early-stage triple-negative breast cancer appear to have better survival rates and a lower risk of recurrence if they carry high levels of cancer-killing immune cells, results show.
Their survival rates remained high even when they didn't receive follow-up chemo after undergoing radiation or surgery to rid themselves of their breast tumor, researchers report April 2 in the Journal of the American Medical Association.
These immune cells, called tumor-infiltrating lymphocytes (TILs), are naturally able to target and attack cancer cells, researchers said.
"The study's findings may inspire future clinical trials to explore whether patients with a favorable prognosis [high TILs] can avoid intensive chemotherapy regimens," said lead researcher Dr. Roberto Leon-Ferre, a breast cancer doctor at the Mayo Clinic Comprehensive Cancer Center.
About 15% of women with breast cancer have triple-negative breast cancer, which does not respond to drugs that target either female hormones or HER2, a protein that promotes cancer growth.
Triple-negative breast cancers are more likely to grow rapidly and spread to other parts of the body, and also are more likely to recur following treatment, researchers said in background notes.
A high level of TILs has long been associated with better outcomes in breast cancer patients, the researchers said in a Mayo Clinic news release.
However, until now no one has thought to examine whether TILs could be used to help doctors better plan a patient's cancer treatment.
"TILs are not currently measured or reported in the routine examination of tissue samples of breast cancer," said co-senior study author Dr. Matthew Goetz, an oncologist at Mayo Clinic Comprehensive Cancer Center.
For the study, researchers collected data on nearly 2,000 patients with early-stage triple-negative breast cancer who received surgery with or without radiation therapy but did not get any chemo. These patients were followed for an average of 18 years.
Five years after surgery, 95% of patients with high TIL levels were still alive, compared to 82% of patients whose tumors had low TIL levels, researchers found.
Further, the recurrence rate for breast cancer was significantly lower among those with high TIL levels, results show.
"The results of this study could lead to a recommendation to include TILs in the pathology reports of early-stage [triple-negative breast cancer] worldwide, as it has the potential to inform clinicians and patients when they discuss treatment options," said co-lead researcher Dr. Roberto Salgado, co-chair of the International Immuno-Oncology Biomarker Working Group.
What's more, it's easy and cheap to look for TILs, the researchers added. A pathologist can check a person's TIL levels by simply examining a breast tumor biopsy under a microscope.
Because triple-negative breast cancers are tougher to treat, most people with early-stage tumors undergo chemotherapy before or after surgery. Many receive multiple chemo drugs, which can cause significant side effects.
Currently, doctors take into account tumor size and whether cancer has spread to the lymph nodes when they decide whether a patient needs chemo, researchers said.
The researchers plan to test in clinical trials whether TILs can be used as a marker to judge the need for chemotherapy.
More information
The American Cancer Society has more on triple-negative breast cancer.
SOURCE: Mayo Clinic, news release, April 2, 2024
