Background: Implementing mammogram screening means that clinicians are seeing many breast cancers that will never develop metastases. The purpose of this study was to identify subgroups of breast cancer patients who did not present events related to long-term breast cancer mortality, taking into account diagnosis at breast screening, absence of palpability and axillary involvement, and genomic analysis with PAM50.
Patients and methods: To identify them, a retrospective observational study was carried out selecting patients without any palpable tumor and without axillary involvement, and a genomic analysis was performed with PAM50.
Results: The probability of distant metastasis-free interval (DMFI) of 337 patients was 0.92 (95% CI, 0.90-0.93) at 20 years and 0.96 (95% CI, 0.92-1.00) in 95 patients (28%) with available PAM50 tests. In 22 (23.15%) luminal A tumors and in 9 (9.47%) luminal B tumors smaller than 1 cm, and in HER2 and basal type tumors, there were no metastatic events (20-year DMFI of 1.00).
Conclusion: Patients with nonpalpable breast cancer found at screening with negative nodes are at very low risk. It is possible to identify subgroups without metastatic events by determining the intrinsic subtype and tumor size less than 1 cm. Therefore, de-escalation of treatment should be considered.
Keywords: low-risk breast cancer; metastasis; observational study; screening.