Triple-negative breast cancer is an aggressive form of breast cancer that tends to grow and metastasize more quickly than other breast cancer types. This type of breast cancer does not have hormone sensitivity and does not respond to hormone therapy as a result. Every year, approximately 2,000 to 3,000 women are diagnosed with triple-negative breast cancer.
Nearly all patients with triple-negative breast cancer receive chemotherapy to prevent metastases. But chemotherapy leads to many side effects and can negatively affect fertility and overall health later in life.
One particular patient group responds very well to the treatment. The tumors of these patients, who face an excellent prognosis, contain a high immune cell count. These cells enter the tumor through the bloodstream to destroy cancer cells. They are also known as tumor-infiltrating lymphocytes: TILs.
Physician researcher Veerle Geurts: “Prior research showed that TILs have a strong prognostic value in patients with early-stage breast cancer, but this data is mainly based on patients treated with chemotherapy, and patients with stage I are not always included in these studies. Patients with stage I TNBC already have a good prognosis, and prior research showed that not all patients benefit from treatment with chemotherapy. We aimed to study whether TILs have prognostic value in patients with stage I triple-negative breast cancer and could help to identify patients with an excellent prognosis without chemotherapy. Some patients face such a positive prognosis that the cons outweigh the pros.”
Using a database from the Dutch Cancer Registry (IKNL), the researchers identified 4,511 patients who had been diagnosed with triple-negative breast cancer between 2005 and 2015 in the Netherlands. Geurts: “Then we requested tissue blocks from all patients who did not receive chemotherapy. The tissue blocks can be used to make a H&E stained slide, on which TILs can be scored by a trained pathologist. We were able to determine TIL-scores for 1041 patients.”
The results: women with a high TIL percentage (30% or more) have a 96% ten-year survival rate, compared to 87% of patients with fewer immune cells without treatment with chemotherapy. Geurts: in patients with a tumor between 1 and 2 cm, known as pT1c-tumors, we observed an even stronger effect; those who had 75% or more immune cells had a breast cancer-specific survival of 98.3 % without chemotherapy.
Medical oncologist and researcher Marleen Kok: “Currently many patients with triple-negative breast cancer receive the standard treatment involving 5 months of chemotherapy with three or four types of chemotherapy drugs. For patients with a high TIL count, this is immense overtreatment.” That’s why a clinical trial will start soon to investigate whether patients with a high TIL count can safely forgo chemotherapy without worsening the prognosis, and whether this improves quality of life.
“It’s interesting that the first report suggests that a high TIL count is associated with a better prognosis in breast cancer patients was released over 100 years ago by physicians from the Mayo Clinic in America”, says Roberto Salgado, M.D., co-president of the International Immuno-Oncology Biomarker Working Group and fellow study leader. “It took worldwide efforts and another century to research this biomarker again and come closer to clinical application.”