# Clinicopathological and Genomic Identification of Breast Cancers with No Impact on Mortality

## TL;DR

This study identifies breast cancer subgroups with low metastasis risk based on tumor characteristics and genomic subtypes, suggesting treatment de-escalation.

## Contribution

The study introduces a method to identify low-risk breast cancer subgroups using tumor size, palpability, and PAM50 subtypes.

## Key findings

- Non-palpable, luminal tumors <1 cm diagnosed via screening show no metastases.
- Luminal A and B tumors <1 cm have 20-year metastasis-free survival rates of 100%.
- PAM50 subtypes and tumor size help identify patients with negligible long-term mortality risk.

## Abstract

There are patients with breast cancer which will never metastasize. Tumor palpability is a prognostic variable for lower risk of developing metastases. PAM50 intrinsic subtypes were independently prognostic for long-term survival. In our study, patients with non-palpable, luminal tumors, <1 cm, diagnosed on breast screening, never develop metastases. De-escalation of treatment should be considered.

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.