Perbandingan Ekspresi Imunohistokimia (IHK) Sebelum dan Sesudah Kemoterapi pada Pasien Kanker Payudara di RSUP H Adam Malik Medan

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