European Journal of Cardiovascular Medicine

Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer-related deaths among women globally, accounting for 11.7% of all new cancer cases and 6.9% of cancer deaths worldwide as of 2020¹. The disease's heterogeneity necessitates a comprehensive approach to diagnosis and treatment planning. Beyond traditional histopathological parameters, biochemical markers have emerged as crucial components for early detection, prognosis, and therapeutic decisions².

Among the biochemical indicators, CA 15-3 and Carcinoembryonic Antigen (CEA) are routinely used serum markers. Elevated levels of CA 15-3 correlate with tumor burden and are often associated with advanced disease stages and metastasis³. Similarly, CEA has been used as a prognostic indicator, especially in tracking disease recurrence⁴. These markers provide non-invasive insights into tumor progression and patient prognosis.

Hormone receptor status plays a pivotal role in defining therapeutic strategies. Estrogen Receptor (ER) and Progesterone Receptor (PR) positivity are commonly associated with a favorable prognosis and responsiveness to hormonal therapies⁵. In contrast, Human Epidermal Growth Factor Receptor 2 (HER2) amplification denotes a more aggressive tumor phenotype and a poor prognosis but also offers a target for monoclonal antibody-based treatments⁶.

Histologically, breast carcinomas are predominantly ductal or lobular. Tumor grading and staging, based on histopathological examination, are crucial for assessing the aggressiveness and extent of disease. Correlating these findings with biochemical indicators can enhance prognostic precision⁷.

Several studies have attempted to delineate the relationship between biochemical markers and tumor histology. For instance, higher CA 15-3 levels have been linked with ductal carcinomas and poor differentiation⁸. Similarly, HER2 overexpression is predominantly found in high-grade invasive ductal carcinomas⁹. Understanding these relationships can help tailor more effective, individualized treatment strategies.

This study aims to investigate the correlation between key biochemical markers (CA 15-3, CEA, ER, PR, HER2) and histological parameters like tumor grade, type, stage, and lymph node involvement. By elucidating these associations, we aim to contribute to the growing body of evidence supporting the integration of biochemical markers into routine breast cancer evaluation.

This hospital-based observational study was conducted in the Department of Pathology and Oncology at a tertiary care institution over a period of 18 months. A total of 150 female patients aged between 30 to 70 years, who were histologically diagnosed with breast carcinoma, were included after obtaining written informed consent.

Inclusion Criteria:

• Female patients aged 30–70 years.
• Histologically confirmed breast carcinoma.
• Patients who had not received prior chemotherapy, radiotherapy, or hormonal therapy.
• Willingness to provide informed consent.

Exclusion Criteria:

• Patients with a history of other malignancies.
• Patients on neoadjuvant therapy.
• Pregnant or lactating women.
• Patients with incomplete clinical or laboratory data.

Clinical Assessment and Sampling:
Detailed clinical evaluation, imaging studies, and staging (TNM classification) were performed. Blood samples were collected before surgery or biopsy. Serum levels of CA 15-3 and CEA were measured using enzyme-linked immunosorbent assay (ELISA). Tumor tissues were subjected to immunohistochemistry (IHC) for estrogen receptor (ER), progesterone receptor (PR), and HER2 status.

Histopathological Evaluation:
Tissue specimens were fixed in 10% formalin and processed for paraffin embedding. Hematoxylin and eosin (H&E) stained sections were examined to determine tumor type, grade (according to the Nottingham grading system), and lymph node involvement.

Biochemical Marker Analysis:
CA 15-3 and CEA levels were categorized as elevated or normal based on manufacturer-provided reference ranges. ER, PR, and HER2 status were scored using the Allred system and ASCO/CAP guidelines.

Statistical Analysis:
Statistical analysis was carried out using SPSS version 22. Chi-square test and ANOVA were applied to assess correlations between biochemical markers and histological variables. A p-value <0.05 was considered statistically significant.

Table 1: Distribution of Patients by Tumor Grade

In table 1, the cohort has predominantly intermediate (Grade II, 46.7%) and high-grade (Grade III, 33.3%) tumors. Low-grade (Grade I) tumors are less common (20%). There's a strong inverse relationship between tumor grade and hormone receptor (ER/PR) positivity. Grade I: Highly hormone receptor positive (83.3% = 25/30). Grade II: Moderately hormone receptor positive (71.4% = 50/70). Grade III: Predominantly hormone receptor negative (60.0% = 30/50 ER/PR negative).

Table 2: Serum CA 15-3 Levels vs. Tumor Stage

In table 2, Stage I: Low elevation rate (20% = 5/25). Stage II: Moderate elevation rate (40% = 20/50). Stage III: High elevation rate (66.7% = 30/45). Stage IV: Very high elevation rate (83.3% = 25/30).

Table 3: CEA Levels and Lymph Node Involvement

In table 3, A normal CEA is strongly associated with the absence of lymph node involvement (88.9% NPV = 80/90 patients with normal CEA were node negative).

Table 4: HER2 Expression by Histological Type

In table 4, HER2 positivity is significantly more common in Ductal Carcinoma (45% = 45/100) compared to Lobular Carcinoma (10% = 5/50).

Table 5: Hormone Receptor (ER/PR) Status and Tumor Grade

Table 6: Combined Biomarker Profile and Patient Prognosis

In table 6, Best Prognosis: The ER+/PR+/HER2- (Luminal A-like) profile shows the most favorable prognosis, with 80% (40/50) having a good prognosis and only 20% (10/50) having a poor prognosis. Worst Prognosis: The ER-/PR-/HER2+ (HER2-enriched non-Luminal) profile shows the poorest prognosis, with 87.5% (35/40) having a poor prognosis and only 12.5% (5/40) having a good prognosis. Intermediate/Mixed Prognosis: The group comprising ER+/PR-/HER2+ or others (which likely includes Luminal B-like and possibly Triple Negative subtypes) shows an unfavorable trend, with 83.3% (50/60) having a poor prognosis.

This study highlights the utility of biochemical markers in predicting the histological behavior of breast carcinoma. Elevated serum levels of CA 15-3 and CEA were significantly associated with higher tumor stages and lymph node metastasis. These findings are consistent with those of Molina et al., who emphasized the prognostic value of CA 15-3 in monitoring disease progression and recurrence. ¹¹ The current study reaffirms that CA 15-3 reflects tumor burden and may serve as a surrogate marker for disease aggressiveness.

CEA, another non-specific tumor marker, showed a strong association with lymph node involvement in our study population. These results are in agreement with prior studies by Duffy et al., which demonstrated CEA as an independent prognostic marker in advanced breast cancer. ¹² While its sensitivity is lower compared to CA 15-3, its specificity increases when used in combination with other markers.

HER2 overexpression was found predominantly in patients with ductal carcinoma, echoing the findings of Slamon et al., who reported that HER2 amplification correlates with poor clinical outcomes and high histological grade. ¹³ This further supports the integration of HER2 testing in routine practice to identify candidates for targeted therapy like trastuzumab.

ER and PR positivity showed a reverse trend with tumor grade. Lower-grade tumors were significantly associated with ER and PR positivity, aligning with the findings of Allred et al., who correlated hormone receptor expression with better prognosis and response to endocrine therapy. ¹⁴ This emphasizes the need for routine hormone receptor assessment in all breast cancer cases.

The combined biomarker profiles further illuminated prognostic groupings. Triple positive (ER+/PR+/HER2−) patients exhibited favorable outcomes, whereas triple negative and HER2-enriched subtypes were linked to poorer prognosis, corroborating with the molecular classification by Perou et al. ¹⁵ This reinforces the concept of intrinsic subtypes and their clinical significance.

Notably, the study also adds to the limited regional data on biochemical-histological correlations in breast cancer, offering a valuable contribution to the Indian cancer research context. Although the sample size was modest, the robust methodology and significant associations observed underscore the reliability of the findings.

This study reinforces the diagnostic and prognostic relevance of key biochemical markers in breast cancer. Elevated CA 15-3 and CEA levels were closely linked with higher tumor grade, lymph node involvement, and advanced clinical stages, indicating their potential as markers for tumor burden and disease progression. HER2 overexpression was significantly associated with aggressive histological types, especially ductal carcinoma, while ER and PR positivity correlated with favorable histological features, such as low-grade and early-stage tumors.

The integration of these biochemical indicators with histopathological evaluation provides a more comprehensive understanding of tumor biology. This dual approach allows for more accurate stratification of patients and facilitates tailored therapeutic decisions, particularly the selection of hormone therapy or HER2-targeted agents. These findings support the routine assessment of biochemical markers, especially in resource-limited settings where molecular profiling may not be feasible.

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