# Effect of Neoadjuvant Chemotherapy on Immunohistochemistry in Breast Cancer

## TL;DR

This study shows that neoadjuvant chemotherapy changes breast cancer markers like ER, PR, HER2, and Ki67, which could affect treatment decisions.

## Contribution

The study demonstrates that neoadjuvant chemotherapy can alter receptor statuses and Ki67 levels in breast cancer patients.

## Key findings

- 8.3% of ER-negative patients converted to ER-positive after neoadjuvant chemotherapy.
- Ki67 levels decreased significantly from 51.7% to 26.28% following treatment.
- 16.6% of HER2-negative patients became HER2-positive post-chemotherapy.

## Abstract

Background

Neoadjuvant chemotherapy (NACT) is a key treatment strategy for locally advanced or high-risk early-stage breast cancer. This study aims to evaluate the effects of NACT on estrogen receptor (ER), progesterone receptor (PR), HER2 status, and Ki67 index, which are crucial markers for breast cancer prognosis and treatment decisions.

Methods

A cohort of 62 female breast cancer patients underwent NACT with varied regimens. Baseline and post-treatment data on ER, PR, HER2 status, and Ki67 were collected through immunohistochemistry and sonomammography. Statistical analysis was performed using R software, with Wilcoxon rank-sum and paired t-tests for primary and secondary outcomes, respectively.

Results

Significant changes were observed in receptor statuses post-NACT. Notably, 8.3% of ER-negative patients converted to ER-positive, 14.2% of PR-negative patients became PR-positive, and 16.6% of HER2-negative patients became HER2-positive. Ki67 levels decreased significantly from 51.7% to 26.28% (p < 0.001), indicating reduced tumor proliferation.

Discussion

The shifts in ER, PR, and HER2 status suggest the dynamic nature of breast cancer during chemotherapy, with implications for personalized treatment strategies. The reduction in Ki67 indicates a favorable tumor response, though tumor heterogeneity and treatment resistance remain challenges. These findings underscore the importance of post-treatment molecular profiling to guide therapy decisions and optimize patient outcomes.

Conclusion

NACT significantly alters the molecular profile of breast cancer, including receptor status and Ki67 levels, which can inform personalized treatment strategies. These findings highlight the need for post-NACT reassessment to tailor follow-up therapies and improve long-term patient outcomes.