Evaluation of Tissue-Based and Serum-Based Tumor Markers in Breast Cancer Patients at the University of Ilorin Teaching Hospital

Abstract

Tissue-based immunohistochemical markers oestrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) remain the standard for molecular characterisation of breast cancer, but their acquisition is invasive, costly, and often inaccessible in resource-constrained settings. Circulating serum tumour markers offer a less invasive alternative, but their correlation with tissue-based receptor status in Nigerian breast cancer patients remains poorly characterised. This cross-sectional study evaluated and correlated tissue-based (ER, PR, HER2) and serum-based (carcinoembryonic antigen [CEA], cancer antigen 15-3 [CA15-3], and cancer antigen 27-29 [CA27-29]) tumour markers among 30 histologically confirmed breast cancer patients attending the University of Ilorin Teaching Hospital. Serum CEA, CA15-3, and CA27-29 were measured by enzyme-linked immunosorbent assay, and ER, PR, and HER2 status were determined by immunohistochemistry on archived tumour tissues. The ER, PR, and HER2 positivity were observed in 63.3%, 36.7%, and 23.3% of participants, respectively; Luminal A was the most frequent inferred molecular subtype (26.7%), followed by triple-negative disease (23.3%). Median CEA, CA15-3, and CA27-29 concentrations were 2.9 ng/mL, 62.7 U/mL, and 111.0 U/mL, respectively. CEA correlated positively with CA15-3 (ρ=0.614, p=0.001) and CA15-3 with CA27-29 (ρ=0.561, p=0.002), but none of the three markers differed significantly by ER, PR, or HER2 status (all p>0.05), and exploratory ROC analysis showed no statistically significant discrimination of ER status (AUC 0.59–0.73, all p>0.05). Serum CEA, CA15-3, and CA27-29 correlate with one another but do not reliably reflect tissue-based receptor status in this cohort, and cannot substitute for immunohistochemistry in receptor classification.