Luminal breast cancer classification according to proliferative indices: clinicopathological characteristics and short-term survival analysis

Are All Prognostic Stage IB Breast Cancers Equivalent?

Background/Objectives: The 8th edition of the American Joint Committee on Cancer integrates histology and biomarker status with anatomic extent in breast cancer (BC) pathologic prognostic staging (PPS). However, PPS IB includes anatomic locally advanced hormone-receptor-positive/HER2-negative (LA-HR+/HER2-) and early-stage triple-negative BC (ES-TNBC). Previous research shows that increased nodal involvement is a critical predictor of worse prognosis, raising questions about whether biological subtype or anatomic stage has a greater influence on outcomes in these discordant cases. We hypothesized that overall survival (OS) remains worse for LA-HR+/HER2- BC compared to ES-TNBC, despite both being classified as PPS IB. Methods: Using the National Cancer Database, we identified patients with LA-HR+/HER2- BC (pT3N1 or pT1-3N2, grade 1-2) and ES-TNBC (T1N0, grade 2-3) treated between 2004 and 2017. Patients without complete primary tumor stage, biomarker status, grade, TNM staging, or treated with neoadjuvant therapy were excluded. The primary endpoint was OS. Multivariable Cox regression evaluated OS between LA-HR+/HER2- BC and ES-TNBC. Results: Among 45,818 patients (17,359 LA-HR+/HER2- BC and 28,459 ES-TNBC), LA-HR+/HER2- BC had significantly worse 6-year OS (86.1% vs. 90.4%; HR = 1.63; p < 0.0001). Among patients receiving appropriate therapies, patients with LA-HR+/HER2- BC had 35% relatively higher risk of death (HR = 1.35; 1.24-1.48; p < 0.0001). These results highlight that LA-HR+/HER2- breast cancer has worse survival compared to ES-TNBC, despite both being classified as PPS IB and receiving all appropriate treatments. Conclusions: Anatomic disease extent remains an important factor in patients with discordant AS and PPS. Future iterations of PPS should re-classify LA-HR+/HER2- breast cancer from PPS IB to ensure more accurate prognostic and survival information.

Risk of recurrence among patients with HR-positive, HER2-negative, early breast cancer receiving adjuvant endocrine therapy: A systematic review and meta-analysis

BACKGROUND

A systematic review and meta-analysis was conducted to assess breast cancer (BC) outcomes among patients with early-stage hormone receptor positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) BC, receiving adjuvant endocrine therapy.

METHODS

Randomized controlled trials (RCTs) and real-world evidence (RWE) studies were identified using Ovid MEDLINE®, Embase, and Evidence-Based Medicine Reviews. Clinical and methodological similarities including alignment of outcome definitions with standardized definitions for efficacy endpoints criteria were assessed to evaluate feasibility of conducting a meta-analysis. Where feasible, 5-year probabilities of BC recurrence or death were estimated using a Bayesian hierarchical arm-based model.

RESULTS

Of 21 included studies, 8 RCTs and 4 RWE studies reported outcome data of interest. There was heterogeneity in outcome reporting, as well as variation in recurrence risk amongst studies with aligned reporting. Of the 12 studies, 10 were considered for inclusion in a meta-analysis of BC recurrence or death. Only a subgroup analysis of node-positive patients (3 studies; n = 7307) was deemed feasible. The 5-year probability of BC recurrence or death was 17.2% (95% credible interval: 14.6%-20.3%).

CONCLUSION

Although studies reporting recurrence outcomes were limited, there remains a high risk of BC recurrence, especially among node-positive patients. Approximately 1 in 6 women with node-positive HR+/HER2- early-stage BC receiving endocrine therapy experience recurrence or death within 5-years of initiating treatment, suggesting a need for novel treatments for this population.

Extensive Transcriptomic and Genomic Analysis Provides New Insights about Luminal Breast Cancers

Despite constituting approximately two thirds of all breast cancers, the luminal A and B tumours are poorly classified at both clinical and molecular levels. There are contradictory reports on the nature of these subtypes: some define them as intrinsic entities, others as a continuum. With the aim of addressing these uncertainties and identifying molecular signatures of patients at risk, we conducted a comprehensive transcriptomic and genomic analysis of 2,425 luminal breast cancer samples. Our results indicate that the separation between the molecular luminal A and B subtypes—per definition—is not associated with intrinsic characteristics evident in the differentiation between other subtypes. Moreover, t-SNE and MST-kNN clustering approaches based on 10,000 probes, associated with luminal tumour initiation and/or development, revealed the close connections between luminal A and B tumours, with no evidence of a clear boundary between them. Thus, we considered all luminal tumours as a single heterogeneous group for analysis purposes. We first stratified luminal tumours into two distinct groups by their HER2 gene cluster co-expression: HER2-amplified luminal and ordinary-luminal. The former group is associated with distinct transcriptomic and genomic profiles, and poor prognosis; it comprises approximately 8% of all luminal cases. For the remaining ordinary-luminal tumours we further identified the molecular signature correlated with disease outcomes, exhibiting an approximately continuous gene expression range from low to high risk. Thus, we employed four virtual quantiles to segregate the groups of patients. The clinico-pathological characteristics and ratios of genomic aberrations are concordant with the variations in gene expression profiles, hinting at a progressive staging. The comparison with the current separation into luminal A and B subtypes revealed a substantially improved survival stratification. Concluding, we suggest a review of the definition of luminal A and B subtypes. A proposition for a revisited delineation is provided in this study.

Aberrant expression of Arpin in human breast cancer and its clinical significance

Arpin (Arp2/3 complex inhibitor), a novel protein found in 2013, plays a pivotal role in cell motility and migration. However, the precise role of Arpin in cancer is unclear. This study investigated the expression of Arpin in breast cancer and evaluated its correlation with the characteristics of clinical pathology and prognosis of breast cancer patients. Immunohistochemistry (IHC) for Arpin protein was performed on formalin‐fixed, paraffin‐embedded 176 breast cancer tissues and 43 normal breast tissues while qRT‐PCR for Arpin mRNA with 104 paired tumour and paratumoural tissues from breast cancer patients respectively. The association of Arpin expression with clinical pathological features and survival was assessed in a retrospective cohort analysis of patients. The results showed that the expression of Arpin protein in cancer tissues was lower compared to that in normal breast and the expression of Arpin mRNA was also lower in cancer tissues than that in the matched paratumoural tissues. Among the 176 breast cancer patients, the lower expression of Arpin was significantly associated with advanced tumour, nodes and metastasis system stage, and the reduced Arpin expression was strongly associated with axillary lymph node metastasis using univariate and multivariate logistic regression analysis [odds ratio: 3.242; 95% confidence interval (CI): 1.526, 6.888; P < 0.05]. Furthermore, Arpin expression was an independent risk factor for recurrence‐free survival (HR: 0.373; 95% CI: 0.171, 0.813; P < 0.05). As Arpin expression was first examined in human breast cancer tissues with qRT‐PCR and IHC, our results suggest that Arpin downregulation may contribute to the initiation and development of breast cancer metastasis. Therefore, as a potential predictive marker, Arpin deserves future studies.