New data coming from a retrospective analysis, recently published on JAMA, demonstrate that tumor-infiltrating lymphocyte (TIL) abundance in breast cancer tissue is a prognostic factor for cancer recurrence and death in patients with early-stage triple-negative breast cancer TNBC.

The study is a pooled analysis of individual patient-level data from 13 participating centers, including 1966 patients diagnosed with TNBC between 1979 and 2017, with a follow-up until 2021, who received treatment with surgery with or without radiotherapy but no adjuvant or neoadjuvant chemotherapy. 21% of patients had a TIL level of 50% or more, 66% had a TIL level of less than 30%; the median TIL level was 15%. Five-year distant recurrence-free survival for stage I TNBC was 94%) for patients with a TIL level of 50% or more, compared with 78% for those with a TIL level of less than 30%; 5-year overall survival was 95%  for patients with a TIL level of 50% or more, compared with 82% for those with a TIL level of less than 30%. At a median follow-up of 18 years, and after adjusting for age, tumor size, nodal status, histological grade, and receipt of radiotherapy, each 10% higher TIL increment was associated independently with improved invasive disease-free survival. As authors conclude, «In patients with early-stage TNBC who did not undergo adjuvant or neoadjuvant chemotherapy, breast cancer tissue with a higher abundance of TIL levels was associated with significantly better survival. These results suggest that breast tissue TIL abundance is a prognostic factor for patients with early stage TNBC».