| dc.description.abstract | Introduction: Breast cancer is the most common malignancy among women in
Indonesia, often diagnosed at advanced stages. Immunohistochemistry (IHC)
markers—estrogen receptor (ER), progesterone receptor (PR), HER2, and Ki
67—are critical for molecular subtype classification, treatment planning, and
prognosis. Chemotherapy may alter these biomarkers, warranting comparative
evaluation before and after treatment.
Methods: This retrospective cohort study analyzed 31 breast cancer patients at H.
Adam Malik General Hospital, Medan, who underwent chemotherapy from
January 2023 to January 2025. Data from medical records and paraffin blocks
were used to assess ER, PR, HER2, and Ki-67 expression pre- and post
chemotherapy. Statistical analysis employed Chi-square or Fisher’s exact test.
Results: Mean patient age was 53.68 years; most had invasive ductal carcinoma
(83.9%), grade 3 tumors (48.4%), and stage III disease (90.3%). The most
common chemotherapy regimen was EC + 5FU (29.03%). Post-chemotherapy,
ER decreased in 61.3% of patients, PR in 61.3%, HER2 in 71%, while Ki-67
increased in 77.4% (all p<0.001). Molecular subtype changes were significant
(p=0.031), with triple-negative breast cancer (TNBC) increasing to 61.3% after
therapy.
Discussion: Findings suggest chemotherapy can induce substantial molecular
changes via clonal selection, gene regulation shifts, and microenvironmental
effects. Loss of ER/PR and HER2 may reduce responsiveness to targeted or
hormonal therapies, while Ki-67 elevation indicates possible tumor repopulation.
Conclusion: Significant alterations in IHC profiles and molecular subtypes occur
after chemotherapy in breast cancer patients. Reassessment of biomarkers post
therapy is essential for optimizing subsequent treatment strategies.
Keywords: breast cancer, immunohistochemistry, chemotherapy, ER, PR, HER2,
Ki-67, molecular subtype | en_US |
