Prognostic impact of reduced HER2 protein expression in post-neoadjuvant therapy resection specimens: A single institution experience and review of the literature

Is switching to T-DM1 still justified in HER2-negative residual breast cancer after neoadjuvant systemic therapy?

The standard of care for HER2-positive and hormone receptor-positive breast cancer patients who receive neoadjuvant chemotherapy (NACT) combined with trastuzumab, with or without pertuzumab, is to continue with adjuvant T-DM1 in cases of an incomplete response according to KATHERINE trial results. However, the optimal management for patients with residual disease with loss of HER2 expression is not widely studied. Loss of HER2 expression after NACT with anti HER2 is a rarer event with questionable value both as a predictive prognostic marker.

Switching to T-DM1 remains justified in patients with HER2-negative residual invasive breast cancer after neoadjuvant therapy

Reductions in HER2-protein IHC intensity and HER2-gene amplification in residual invasive breast cancer following neoadjuvant therapy for HER2-positive breast cancer have been described and are associated with worse outcomes. T-DM1 requires initial binding to HER2 for activity, so concerns have been raised regarding T-DM1 activity when changes are sufficient to classify residual disease as HER2-negative. The KATHERINE trial assessed HER2 status of residual disease from 845 patients with HER2-positive status on pretherapy biopsies, of which 70 were negative on retesting. With 8 years of median follow-up, 7-year IDFS was 60.3 % with trastuzumab compared to 95.2 % with T-DM1, consistent with clinically meaningful benefit from T-DM1 in these 70 patients.

Personalized multifactorial risk assessment in neoadjuvant-treated breast carcinoma

PURPOSE

Due to biological heterogeneity of breast carcinoma, predicting the individual response to neoadjuvant treatment (NAT) is complex. Consequently, there are no comprehensive, generally accepted practices to guide post-treatment follow-up. We present clinical and histopathological criteria to advance the prediction of disease outcome in NA-treated breast cancer.

METHODS

A retrospective consecutive cohort of 257 NA-treated Finnish breast cancer patients with up to 13-year follow-up and the corresponding tissue samples of pre- and post-NAT breast and metastatic specimen were evaluated for prognostic impacts. All relevant clinical and biomarker characteristics potentially correlated with tumor response to NAT, course of disease, or outcome of breast cancer were included in the statistical analyses.

RESULTS

The results highlight the intensified characterization of distinguished prognostic factors and previously overlooked histological features, e.g., mitotic and apoptotic activity. Particularly, decreased PR indicated 3.8-fold (CI 1.9-7.4, p = 0.0001) mortality risk, and a > 10.5-year shorter survival for the majority, > 75% of patients (Q1). Clinically applicable prognostic factors both preceding and following NAT were identified and compiled into heat maps to quantify mortality and recurrence risks. Combinations of risk factors for aggressive disease were exemplified as an interactive tool (bcnatreccalc.utu.fi) to illustrate the spectrum of disease outcomes.

CONCLUSION

The results emphasize the value of comprehensive evaluation of conventional patient and biomarker characteristics, especially concerning re-assessment of biomarkers, risk-adapted surveillance, and personalized treatment strategies. Future personalized NA-treatment strategies might benefit from models combining risk-adapted surveillance data and post-NAT re-assessed biomarkers.

Impact of loss of HER2 positivity following neoadjuvant therapy in HER2-positive breast cancer patients on long-term prognosis: A systematic review and meta-analysis

AIMS

The primary objective was to assess the impact of HER2 loss after neoadjuvant therapy on the long-term prognosis of patients with HER2-positive breast cancer.

METHODS

We extracted relevant studies from PubMed and Cochrane Library and performed systematic review and meta-analysis. The key eligibility criteria for the studies were as follows: included HER2-positive early breast cancer cases undergoing neoadjuvant therapy, available data on HER2 status before and after neoadjuvant therapy, and reported recurrence-related outcomes (disease-free survival/invasive disease-free survival/relapse-free survival) or overall survival.

RESULTS

Of 915 studies that were initially identified, 8 met the eligibility criteria and were included in the meta-analysis for the recurrence-related outcomes (1,917 patients with HER2 loss: 411 [21.4 %] or HER2 retained: 1,506 [78.6 %]); 4 of them reported data on overall survival (606 patients with HER2 loss: 243 [40.1 %] or HER2 retained: 363 [59.9 %]). The average follow-up duration, based on data from five out of eight studies that reported this information, was 51.6 months. HER2 loss was significantly associated with worse recurrence-related outcomes (hazards ratio [HR] 1.85, 95 % confidence interval [CI] 1.31-2.61, p = 0.0005) and worse overall survival (HR 2.37, 95 % CI 1.27-4.41, p = 0.0065). No heterogeneity or publication bias was observed in the meta-analysis.

CONCLUSIONS

This study demonstrated that compared with patients with HER2 retained, those with HER2 loss had significantly higher risk of disease recurrence and worse prognosis. These findings implied the possible use of HER2 loss as a prognostic factor in patients with HER2-positive early breast cancer. Reassessment of HER2 status after neoadjuvant therapy could be valuable in predicting prognosis and may lead to reconsideration of the rational subsequent treatment.

Evolution of HER2 expression between pre-treatment biopsy and residual disease after neoadjuvant therapy for breast cancer

INTRODUCTION

We have previously found that HER2 expression is dynamic, and can change from the primary breast tumor to matched recurrences. With this work, we aimed to assess the dynamics of HER2 during neoadjuvant treatment.(NAT).

METHODS

We reviewed HER2 expression in pre- and post-treatment samples from consecutive patients with early-stage breast cancer that received NAT and underwent surgery at Dana-Farber Brigham Cancer Center between 01/2016-08/2022. The primary outcome was evolution of HER2 expression from pre- to post-NAT specimens in patients with residual disease.

RESULTS

Among 1613 patients receiving NAT, 1080 had residual disease at surgery. A total of 319 patients (29.5%) experienced a change in HER2 expression (HER2 0 vs. HER2-low vs. HER2-positive) from the pre-treatment sample to residual disease, with roughly equal distribution between decreased (50.5%) and increased HER2 expression (49.5%). Similar rates of change in HER2 expression were observed with anthracycline-based (31.8%) or taxane/platinum-based regimens (32.4%). Patients with HER2-0 or HER2-low tumors at diagnosis were likelier to experience a change in HER2 expression post-NAT compared to HER2-positive (32.3% vs. 21.3%, p < 0.001). Changes in HER2 expression post-NAT were prognostic among patients with HER2-positive tumors at diagnosis (3-year recurrence-free survival for change vs. no change: 71.6% vs. 89.6%, p = 0.006) but not among those with HER2-negative tumors at diagnosis (3-year recurrence-free survival for change vs. no change: 79.3% vs. 81.1%, p = 0.31).

CONCLUSIONS

Nearly 30% of patients with early-stage breast cancer showed a change in HER2 expression after NAT. Changes in HER2 expression post-NAT were only prognostic in the setting of HER2-positive tumors becoming HER2-negative at surgery.