# Breast cancer in northern Peru: molecular subtypes and HER2 low

## TL;DR

This study analyzed breast cancer subtypes in northern Peru and found that luminal B is the most common, with a notable HER2 low subgroup.

## Contribution

Identified the HER2 low subgroup in breast cancer patients in northern Peru and highlighted the shift in subtype prevalence.

## Key findings

- Luminal B subtype was most prevalent (45.6%) in northern Peruvian breast cancer patients.
- HER2 low was identified in 25.1% of patients previously classified as HER2 negative.
- The study emphasizes the need for targeted therapies for HER2 low patients in health policies.

## Abstract

This study aimed to understand the immunohistochemical profile of breast cancer and to identify the HER2 low subgroup in the northern macro-region of Peru. A cross-sectional study was conducted in 1176 patients from the Regional Institute of Neoplastic Diseases Northern Peru, from January 2016 to December 2023. We analyzed the data (age, histological type, grade and complementary results), with frequencies and percentages. The profile corresponded to: luminal B (45.6%); luminal A (24.7%); triple negative (18.2%); and HER2 positive non luminal (11.5%). In addition, 215 patients presented HER2 low (25.1% of those previously considered negative). This study provides evidence that the subtyping of breast cancer has changed, being luminal B the most frequent. It is essential to involve health policies to acquire targeted therapies considering HER2 low patients.

El objetivo del estudio fue conocer el perfil inmunohistoquímico del cáncer de mama e identificar el subgrupo HER2 low en la macrorregión norte del Perú. Se realizó un estudio transversal con una muestra de 1176 pacientes atendidos en el Instituto Regional de Enfermedades Neoplásicas Norte del Perú desde enero de 2016 a diciembre de 2023. Los datos recolectados (edad, tipo histológico, grado y resultados complementarios), se analizaron con frecuencias y porcentajes. El perfil correspondió a: luminal B (45,6%); luminal A (24,7%); triple negativo (18,2%); y HER2 positivo no luminal (11,5%). Además, HER2 low fueron 215 pacientes (25,1% de los considerados previamente negativos). Este estudio proporciona evidencia que la subtipificación de cáncer de mama ha cambiado, siendo luminal B más frecuente, y es esencial involucrar a políticas de salud para adquirir terapias dirigidas considerando a pacientes HER2 low.