Discordance in biomarker expression between primary breast cancers and loco-regional recurrences: a comprehensive analysis of 112 cases

Introduction

Breast cancer, characterized by diverse morphological, biological, and clinical subtypes, poses a significant challenge in terms of treatment response (1). Biomarkers such as estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2) play a crucial role in guiding therapeutic decisions for both primary and recurrent breast cancer, influencing choices related to chemotherapy, targeted therapy, or endocrine therapy (2).

Existing evidence suggests that biomarkers like ER, PR, HER2, and Ki-67 may exhibit varied expression patterns in primary and recurrent breast cancers, attributed to clonal heterogeneity and altered receptor expression following treatment (3,4). While treatment guidelines for primary breast cancer are grounded in biomarker expression, uncertainties persist regarding the characteristics and clinical relevance of these biomarkers in recurrent breast cancer (5-9). An unmet need exists to assess biomarker expression in recurrent breast cancers, compare them to primary tumors, and discern the impact of biomarker conversion on systemic therapy choices and prognosis.

The primary aim of this study was to investigate discordance in the status of specific biomarkers between primary breast cancers and loco-regional recurrences, alongside exploring the clinical and pathological characteristics of patients affected by this discordance. We present this article in accordance with the REMARK reporting checklist (available at https://gs.amegroups.com/article/view/10.21037/gs-24-364/rc).

Methods

This retrospective study involved a comprehensive chart review of de-identified patient data. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The ethical committee at Peking Union Medical College Hospital exempted the study from full Institutional Review Board (IRB) review (No. S-K1612) and because of the retrospective nature of this study, the need for informed consent was waived. The research complied with ethical guidelines.

Patients

A total of 112 patients diagnosed with primary breast cancer, presenting with loco-regional recurrence between July 2005 and March 2018 at Peking Union Medical College Hospital, were included in this study. Inclusion criteria were: (I) age ≥18 years; (II) pathological diagnosis of primary breast cancer; and (III) pathological diagnosis of loco-regional recurrence of breast cancer. Exclusion criteria were: (I) male gender or (II) pathological diagnosis of distant metastasis.

Diagnostic approaches

Pathology served as the gold standard for breast cancer diagnosis, categorized according to the World Health Organization (WHO) Classification of Tumors of the Breast (10). Expression levels of hormone receptors (ER, PR) and Ki-67 were evaluated, and HER2 status was assessed by immunohistochemistry (IHC). Tumors with HER2 IHC 3+ were considered positive, IHC 1+ or 0 as negative, and IHC 2+ tumors underwent HER2 gene amplification testing. The Ki-67 proliferation index was determined with a cut-off value of 14%. Tumor subtypes were classified as luminal A, luminal B, HER2 overexpression, and basal-like according to the 13th St Gallen International Breast Cancer Conference [2013] Expert Panel (11).

Data collection

A retrospective review of the patient’s medical records included primary and recurrent tumor characteristics, surgical procedures, history of systemic therapy, presence and medical care of recurrence, disease-free survival (DFS), and overall survival (OS).

Statistical analyses

Statistical analyses were conducted using SPSS v20.0. Fisher’s exact test and the t-test were employed to compare pathological and clinical characteristics of primary and recurrent tumors. A significance level of P<0.05 was considered statistically significant.

Results

Patient characteristics and follow-up

A retrospective review of 8,676 patients diagnosed with primary breast cancer between July 2005 and August 2018 at Peking Union Medical College Hospital identified 143 patients with a pathological diagnosis of recurrent or metastatic breast cancer. After excluding 31 patients with distant metastasis, the final analysis included 112 patients with loco-regional recurrence of breast cancer. The median follow-up duration was 48.3 months (range, 9.1–210.8 months). Subsequently, seven patients died, with causes attributed to subsequent distant metastasis (n=5), cerebrovascular accident (n=1), and radiation pneumonitis (n=1).

The clinical characteristics of the included patients are summarized in Table 1. The mean age at the diagnosis of primary breast cancer was 48.7 years (range, 23–88 years). Primary tumors had a median maximum diameter of 1.6 cm (range, 0.2–12 cm). Treatment for primary breast cancer involves various approaches, including mastectomy with axillary lymph node (LN) dissection, lumpectomy with axillary LN dissection, mastectomy with sentinel LN biopsy, lumpectomy with sentinel LN biopsy, or lumpectomy without axillary LN staging in older patients.

A significant portion of patients (85 out of 112, or 75.9%) underwent chemotherapy for primary breast cancer treatment. Most of them received adjuvant chemotherapy, with initiation occurring 2 to 4 weeks after surgery. Three patients were treated with neoadjuvant chemotherapy. HER2-negative patients were given combinations including doxorubicin/epirubicin plus cyclophosphamide (CTX), docetaxel plus CTX, paclitaxel/docetaxel plus doxorubicin, or docetaxel combined with doxorubicin/epirubicin plus CTX. As for HER2-positive patients, they received regimens involving docetaxel plus CTX plus trastuzumab, as well as doxorubicin plus CTX followed by docetaxel plus trastuzumab or trastuzumab plus pertuzumab. Treatment protocols included doses of doxorubicin/epirubicin (50/75 mg/m²), CTX (500 mg/m²), paclitaxel/docetaxel (175/75 mg/m² q3weeks), trastuzumab (8 mg/kg IV on day 1, then 6 mg/kg q3weeks), and pertuzumab (840 mg for the initial dose, followed by 420 mg q3weeks). Anti-HER2 therapy was administered for 1 year.

Additionally, 45 patients received adjuvant radiotherapy for primary breast cancer. For breast-conserving therapy, whole-breast irradiation was administered through opposed tangential fields, using a regimen of 50 Gy in 2 Gy daily fractions with 6 MV-X rays from a linear accelerator. Patients with invasive disease received a boost of 10 Gy in 5 fractions targeting the tumor bed and 1–2 cm margins. Regional nodal irradiation included the lower portion of the ipsilateral axillary lymph nodes for all cases, and the upper part was included if there were metastases. Following mastectomy, patients received 45–50 Gy at 2 Gy per fraction to the chest wall and supraclavicular fossa. High-risk patients received an electron boost to increase the scar dose to 60–66 Gy.

Moreover, 85 patients (75.9%) underwent endocrine therapy for primary breast cancer, using medications such as tamoxifen (10 mg twice daily or 20 mg once daily), letrozole (2.5 mg daily), anastrozole (1 mg daily), exemestane (25 mg daily), or a goserelin acetate 3.6 mg depot administered subcutaneously every 4 weeks. Most patients completed 5 years of adjuvant endocrine therapy, while those at higher risk of recurrence were treated for 5 to 10 years.

Biomarker expression

ER, PR, HER2, and the Ki-67 index positive status in primary breast cancers and loco-regional recurrences by tissue site are shown in Table 2. There were no significant differences in positive status between primary breast cancers and loco-regional recurrences. There was discordance in the expression of individual biomarkers between primary breast cancers and loco-regional recurrences (Table 3). The discordance rate of ER expression was 9.8% (11/112); the discordance rate of PR expression was 15.2% (17/112); the discordance rate of HER2 expression was 7.6% (8/105); and the discordance rate of the Ki-67 index was 20.6% (21/102).

Patients were treated according to the biomarker status of the loco-regional recurrences with surgery (98.2%, 110/112), radiotherapy (41.1%, 46/112), rescue chemotherapy (61.6%, 69/112), additional endocrine therapy or changes to their original therapy (50.0%, 56/112), or anti-HER2 therapy (10.7%, 12/112). The choice of rescue radiotherapy was individualized, and determined according to the cumulative dose of previous radiotherapy and the location and characteristics of the recurrence. Rescue chemotherapy was selected as a single drug or combination, including oral capecitabine, depending on the clinical characteristics of the recurrence and the patient’s condition. Twelve patients received anti-HER2 treatment.

Discordance in the expression of individual biomarkers between primary breast cancers and loco-regional recurrences varied by breast cancer subtype (Table 4). The discordance rate was highest for luminal A (81.8%) and lowest for TN (9.1%) tumors.

DFS

DFS analysis was conducted, categorizing patients based on the subtype of primary breast cancer or loco-regional recurrence, site of recurrence, and LN status (Figure 1). A notable correlation between DFS and the subtype of primary breast cancer was observed (P=0.002). However, no significant associations were identified between DFS and the subtype of loco-regional recurrence, site of recurrence, or LN status (P>0.05).

Figure 1 Patient prognosis. (A) Relationship between DFS and molecular types of primary breast cancer. (B) Relationship between DFS and molecular types of recurrent breast cancer. (C) Relationship between DFS and different sites of recurrence. (D) Relationship between DFS and lymph node status at operation. HER2+, human epidermal growth factor receptor-2 positive; LRAM, local recurrence after mastectomy; LRAL, local recurrence after lumpectomy; RR, regional recurrence; DFS, disease free survival.

Discussion

Breast cancer, characterized by diverse phenotypic and genetic subtypes, involves the use of biomarkers throughout its management for informed clinical decision-making (12). Notably, the biomarker status of primary and recurrent lesions may differ, necessitating a change in treatment based on these changes (13). Therefore, it is recommended to perform biopsies in patients with recurrent breast cancer (14,15).

The current study revealed discordance in the expression of individual biomarkers between primary breast cancers and loco-regional recurrences, with the discordance rate varying across breast cancer subtypes. Specifically, the discordance rate for ER expression was 9.8%, for PR expression was 15.2%, for HER2 expression was 7.6%, and for the Ki-67 index, it was 20.6% (21/102). The highest discordance rate was observed for luminal A tumors (81.8%), while the lowest was for TN tumors (9.1%).

Earlier studies have reported varying rates of discordance in receptor status between primary breast tumors and recurrent disease, encompassing rates of 10% to 30% for ER expression, 20% to 50% for PR expression, and generally low HER2 discordance between primary tumors and axillary LN or distant metastases (2,6,9,11). Notably, the discordance rates observed in the current study are comparatively lower than those reported previously, particularly for PR, possibly due to the exclusion of patients with distant metastasis in this study.

Guidelines for managing recurrent breast cancer advocate for obtaining the biomarker status of the recurrent tumor. Treatment strategies are personalized, incorporating options such as surgery or radiotherapy. Our recommendation aligns with existing guidelines, emphasizing the importance of biomarker testing in recurrent breast cancers to inform decisions regarding rescue chemotherapy, endocrine therapy, and targeted therapy (9). In this study, corresponding changes were made to the treatment plan of patients based on the immunohistochemistry of loco-regional recurrences, including chemotherapy, radiotherapy, endocrine therapy, and anti-HER2 therapy.

DFS or tumor response often serves as a surrogate endpoint for survival in advanced breast cancer (16,17). In this study, a significant association was observed between DFS and the subtype of primary breast cancer, with the shortest DFS noted in patients with HER2-positive and triple negative (TN) primary breast tumors. Adjuvant systemic therapy for HER2-positive breast cancer typically involves trastuzumab, tyrosine kinase inhibitors, antibody-drug conjugates, and pertuzumab. The findings from this study validate the efficacy of anti-HER2 therapy as adjuvant systemic treatment in HER2-positive breast cancer (18-20). TN breast cancer poses challenges in treatment; however, recent advancements suggest a potential role for immunotherapy (21,22).

Accumulating evidence indicates the acquisition of genomic alterations during cancer development, treatment, and recurrence (23), which may provide valuable insights for clinical decision-making (24-26). Notably, heterogeneous expression of ER, PR, and HER2 can be observed in primary tumors at different anatomical sites and between primary tumors and their corresponding metastatic or recurrent lesions (27,28). Currently, ER, PR and HER2 status are routinely assessed by immunohistochemistry in primary breast cancers as part of standard clinical practice. Exploring alternative approaches may be necessary to further elucidate the spatial and temporal intratumor heterogeneity in primary and recurrent breast cancers (29).

How to distinguish between true tumor recurrence and secondary primary cancer is worth further discussion. It is difficult to distinguish in clinical work, and it is necessary to make a comprehensive judgment based on pathological characteristics, clinical manifestations, and even genetic testing. Generally, recurrence of breast cancer mostly occurs within 6 months after surgery, is located near the surgical incision of the same breast, and the pathological type is the same as the surgically resected lesion. Lowry KP reports that the risk of developing a second primary tumor is associated with the time of recurrence and ER expression (30).

This study represents one of the largest single-center investigations into the discordance in the expression of specific biomarkers between primary breast cancers and loco-regional recurrences and its impact on clinical practice and prognosis. Despite its contributions, several limitations should be acknowledged. Firstly, being a retrospective chart review, the study is susceptible to selection bias. Additionally, as a long-term study, changes in diagnostic criteria and treatment protocols over time may have influenced the outcomes. Factors such as tumor cell metastasis, variations in reagents and antibodies, and diverse experimental conditions might have affected the recorded percentage of positive cells. In addressing these issues, data were reported as originally recorded in patients’ medical records, with some pathological sections re-stained when findings were inconclusive, and patients with missing information were excluded. Lastly, the sample size was restricted due to the necessity of matching findings for pathologically diagnosed primary breast cancer and recurrent tissue.

Conclusions

In conclusion, this is one of the largest single-center studies. The highest discordance rate was observed in luminal A tumors, while the lowest was in triple-negative tumors. DFS was notably shorter in patients with HER2-positive and triple-negative primary breast tumors. Discordance rates in this study were lower than those in previous reports, likely attributed to the exclusion of patients with distant metastasis. The study underscores the importance of biomarker testing in recurrent breast cancers to inform decisions regarding rescue chemotherapy, endocrine therapy, and targeted therapy.

Acknowledgments

We would like to thank Mr. Yongshen Jing who helped us edit the figures.

Funding: None.

Footnote

Reporting Checklist: The authors have completed the REMARK reporting checklist. Available at https://gs.amegroups.com/article/view/10.21037/gs-24-364/rc

Data Sharing Statement: Available at https://gs.amegroups.com/article/view/10.21037/gs-24-364/dss

Peer Review File: Available at https://gs.amegroups.com/article/view/10.21037/gs-24-364/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://gs.amegroups.com/article/view/10.21037/gs-24-364/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The ethical committee of Peking Union Medical College Hospital determined that this study was exempt from full IRB review (No. S-K1612) and granted a waiver of informed consent before the commencement of the study due to the retrospective nature of this study. All methods in our study were carried out under relevant guidelines and regulations.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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