TOPLINE:
Patients with stage I triple-negative breast cancer (TNBC) who have higher levels of stromal tumor-infiltrating lymphocytes (TILs) demonstrate "excellent" 10-year breast cancer–specific survival without chemotherapy, according to new findings, which suggest that stromal TILs could be a useful biomarker to optimize treatment decisions in this patient population.
METHODOLOGY:
- The absolute benefit of chemotherapy remains unclear among patients with stage I TNBC. High levels of stromal TILs, a promising biomarker, have been linked to better survival in patients with TNBC, but data focused on stage I disease are lacking.
- In the current analysis, researchers identified a cohort of 1041 women (mean age at diagnosis, 64.4 years) from the Netherlands Cancer Registry with stage I TNBC who had an available TIL score and had undergone a lumpectomy or a mastectomy but had not received neoadjuvant or adjuvant chemotherapy.
- Patients' clinical data were matched to their corresponding pathologic data provided by the Dutch Pathology Registry, and a pathologist blinded to outcomes scored stromal TIL levels according to the International Immuno-Oncology Biomarker Working Group guidelines.
- The primary endpoint was breast cancer–specific survival at prespecified stromal TIL cutoffs of 30%, 50%, and 75%. Secondary outcomes included specific survival by pathologic tumor stage and overall survival.
TAKEAWAY:
- Overall, 8.6% of women had a pT1a tumor, 38.7% had a pT1b tumor, and 52.6% had a pT1c tumor. In the cohort, 25.6% of patients had stromal TIL levels of 30% or higher, 19.5% had levels of 50% or higher, and 13.5% had levels of 75% or higher.
- Over a median follow-up of 11.4 years, 335 patients died, 107 (32%) of whom died from breast cancer. Patients with smaller tumors (pT1abNO) had better survival outcomes than those with larger tumors (pT1cNO) — a 10-year breast cancer–specific survival of 92% vs 86%, respectively.
- In the overall cohort, stromal TIL levels of 30% or higher were associated with better breast cancer–specific survival than those with stromal TIL levels below 30% (96% vs 87%; hazard ratio [HR], 0.45). Stromal TIL levels of 50% or greater were also associated with better 10-year breast cancer–specific survival than those with levels below 50% (92% vs 88%; HR, 0.59). A similar pattern was observed for stromal TIL levels and overall survival.
- In patients with pT1c tumors, the 10-year breast cancer–specific survival among those with stromal TIL levels of 30% or higher was 95% vs 83% for levels below the 30% cutoff (HR, 0.24). Similarly, the 10-year breast cancer–specific survival for those in the 50% or higher group was 95% vs 84% for levels below that cutoff (HR, 0.27). The 10-year breast cancer–specific survival improved to 98% among patients with stromal TIL levels of 75% or higher (HR, 0.09).
IN PRACTICE:
The results supported the establishment of "treatment-optimization clinical trials in patients with stage I TNBC, using [stromal] TIL level as an integral biomarker to prospectively confirm the observed excellent survival when neoadjuvant or adjuvant chemotherapy is not administered," the authors wrote. Assessing stromal TILs is also "inexpensive," the authors added.
SOURCE:
The research, conducted by Marleen Kok, MD, PhD, Department of Medical Oncology, the Netherlands Cancer Institute, Amsterdam, and colleagues, was published online last month in JAMA Oncology.
LIMITATIONS:
The authors noted that the study was limited by its observational nature. The patients were drawn from a larger cohort, about half of whom received adjuvant chemotherapy, and the patients who did not receive chemotherapy may have had favorable tumor characteristic. There were also no data on BRCA1 or BRCA2 germline mutation status and recurrences and/or distant metastases. The database did not include data on patient ethnicity because most Dutch patients were White.
DISCLOSURES:
Research at the Netherlands Cancer Institute was supported by institutional grants from the Dutch Cancer Society and the Dutch Ministry of Health, Welfare and Sport. Kok declared financial relationships with several organizations including Gilead and Domain Therapeutics, as well as institutional grants from AstraZeneca, BMS, and Roche. Other authors also declared numerous financial relationships for themselves and their institutions with pharmaceutical companies.