Surgical Interest of an Accurate Real-World Prediction of Primary Systemic Therapy Response in HER2 Breast Cancers

Human epidermal growth factor receptor 2 (HER2)-enriched breast cancers (BC) present the highest rates of pathological response to primary systemic therapy (PST), but they are also the ones that tend to be larger at diagnosis, with microcalcifications and, often, with axillary involvement. If we do not have a reliable method to predict the degree of response, we may not be able to transfer the benefits of PST to surgery. The post-PST surgery planning is guided by the findings in the magnetic resonance imaging (MRI), whose predictive capacity, although high, is far from optimal. Thus, it seems interesting to find other variables to improve it. A retrospective observational study including women with HER2 BC treated with PST and further surgery was conducted. Information regarding clinical, radiological, and histopathological variables was gathered from a total of 132 patients included. Radiological complete response (rCR) was achieved in 65.9% of the sample, and pathological complete response (pCR), according to Miller and Payne criteria, in 58.3% of cases. A higher Ki67 value, the absence of Hormonal Receptors expression, and an rCR was significantly related to a pCR finding. This information impacts directly in surgery planning, as it permits adjustment of the breast resection volume.

HER2-targeted therapies - a role beyond breast cancer

HER2 is an established therapeutic target in a large subset of women with breast cancer; a variety of agents including trastuzumab, pertuzumab, lapatinib, neratinib and trastuzumab emtansine (T-DM1) have been approved for the treatment of HER2-positive breast cancer. HER2 is also overexpressed in subsets of patients with other solid tumours. Notably, the addition of trastuzumab to first-line chemotherapy has improved the overall survival of patients with HER2-positive gastric cancer, and has become the standard-of-care treatment for this group of patients. However, trials involving pertuzumab, lapatinib and T-DM1 have failed to provide significant improvements in the outcomes of patients with HER2-positive gastric cancer. HER2-targeted therapies are also being tested in patients with other solid tumours harbouring HER2 overexpression, and/or amplifications or other mutations of the gene encoding HER2 (ERBB2), including biliary tract, colorectal, non-small-cell lung and bladder cancers. The experience with gastric cancer suggests that the successes observed in HER2-positive breast cancer might not be replicated in these other tumour types, owing to differences in the level of HER2 overexpression and other aspects of disease biology. In this Review, we describe the current role of HER2-targeted therapies beyond breast cancer and also highlight the potential of novel HER2-targeted agents that are currently in clinical development.

p95HER2 Methionine 611 Carboxy-Terminal Fragment Is Predictive of Trastuzumab Adjuvant Treatment Benefit in the FinHer Trial

Purpose: Expression of p95HER2 (p95), a truncated form of the HER2 receptor, which lacks the trastuzumab binding site but retains kinase activity, has been reported as a prognostic biomarker for poor outcomes in patients with trastuzumab-treated HER2-positive metastatic breast cancer. The impact of p95 expression on trastuzumab treatment efficacy in early HER2-positive breast cancer is less clear. In the current study, p95 was tested as a predictive marker of trastuzumab treatment benefit in the HER2-positive subset of the FinHer adjuvant phase III trial.Experimental Design: In the FinHer trial, 232 patients with HER2-positive early breast cancer were randomized to receive chemotherapy plus 9 weeks of trastuzumab or no trastuzumab treatment. Quantitative p95 protein expression was measured in formalin-fixed paraffin-embedded samples using the p95 VeraTag assay (Monogram Biosciences), specific for the M611 form of p95. Quantitative HER2 protein expression was measured using the HERmark assay (Monogram Biosciences). Distant disease-free survival (DDFS) was used as the primary outcome measure.Results: In the arm receiving chemotherapy only, increasing log₁₀(p95) correlated with shorter DDFS (HR, 2.0; P = 0.02). In the arm receiving chemotherapy plus trastuzumab (N = 95), increasing log₁₀(p95) was not correlated with a shorter DDFS. In a combined analysis of both treatment arms, high breast tumor p95 content was significantly correlated with trastuzumab treatment benefit in multivariate models (interaction P = 0.01).Conclusions: A high p95HER2/HER2 ratio identified patients with metastatic breast cancer with poor outcomes on trastuzumab-based therapies. Further investigation of the p95HER2/HER2 ratio as a potential prognostic or predictive biomarker for HER2-targeted therapy is warranted. Clin Cancer Res; 24(13); 3046-52. ©2018 AACR.

Mechanisms Behind the Resistance to Trastuzumab in HER2-Amplified Breast Cancer and Strategies to Overcome It

The introduction of trastuzumab therapy markedly improved the poor prognosis associated with HER2-amplified breast cancers. Despite this, the presence of primary and acquired resistance to trastuzumab treatment remains a significant common challenge. The identification of resistance mechanisms and the incorporation of new drugs that achieve a better blockade of HER family receptors signaling have resulted in improved outcomes. The phosphatidylinositol 3′-kinase/protein kinase B/mammalian target of rapamycin pathway, cross-talk with estrogen receptors, immune response, cell cycle control mechanisms, and other tyrosine kinase receptors such as insulin-like growth factor I receptor are potential pathways involved in trastuzumab resistance. Different therapeutic interventions targeting these pathways are currently under evaluation.

Prospective Biomarker Analysis of the Randomized CHER-LOB Study Evaluating the Dual Anti-HER2 Treatment With Trastuzumab and Lapatinib Plus Chemotherapy as Neoadjuvant Therapy for HER2-Positive Breast Cancer

BACKGROUND

The CHER-LOB randomized phase II study showed that the combination of lapatinib and trastuzumab plus chemotherapy increases the pathologic complete remission (pCR) rate compared with chemotherapy plus either trastuzumab or lapatinib. A biomarker program was prospectively planned to identify potential predictors of sensitivity to different treatments and to evaluate treatment effect on tumor biomarkers.

MATERIALS AND METHODS

Overall, 121 breast cancer patients positive for human epidermal growth factor 2 (HER2) were randomly assigned to neoadjuvant chemotherapy plus trastuzumab, lapatinib, or both trastuzumab and lapatinib. Pre- and post-treatment samples were centrally evaluated for HER2, p95-HER2, phosphorylated AKT (pAKT), phosphatase and tensin homolog, Ki67, apoptosis, and PIK3CA mutations. Fresh-frozen tissue samples were collected for genomic analyses.

RESULTS

A mutation in PIK3CA exon 20 or 9 was documented in 20% of cases. Overall, the pCR rates were similar in PIK3CA wild-type and PIK3CA-mutated patients (33.3% vs. 22.7%; p = .323). For patients receiving trastuzumab plus lapatinib, the probability of pCR was higher in PIK3CA wild-type tumors (48.4% vs. 12.5%; p = .06). Ki67, pAKT, and apoptosis measured on the residual disease were significantly reduced from baseline. The degree of Ki67 inhibition was significantly higher in patients receiving the dual anti-HER2 blockade. The integrated analysis of gene expression and copy number data demonstrated that a 50-gene signature specifically predicted the lapatinib-induced pCR.

CONCLUSION

PIK3CA mutations seem to identify patients who are less likely to benefit from dual anti-HER2 inhibition. p95-HER2 and markers of phosphoinositide 3-kinase pathway deregulation are not confirmed as markers of different sensitivity to trastuzumab or lapatinib.

IMPLICATIONS FOR PRACTICE

HER2 is currently the only validated marker to select breast cancer patients for anti-HER2 treatment; however, it is becoming evident that HER2-positive breast cancer is a heterogeneous disease. In addition, more and more new anti-HER2 treatments are becoming available. There is a need to identify markers of sensitivity to different treatments to move in the direction of treatment personalization. This study identified PIK3CA mutations as a potential predictive marker of resistance to dual anti-HER2 treatment that should be further studied in breast cancer.

High HER2 expression correlates with response to the combination of lapatinib and trastuzumab

PURPOSE

Expression of p95HER2 has been associated with resistance to trastuzumab-based therapy in patients with metastatic breast cancer. Conversely, high levels of HER2 have been linked with increased clinical benefit from anti-HER2 therapy. In this work, we aimed to investigate whether the levels of p95HER2 and HER2 can predict response to anti-HER2 therapy in patients with breast cancer.

EXPERIMENTAL DESIGN

We measured p95HER2 and HER2 by VeraTag and HERmark, respectively, in primary tumors of patients enrolled in the neoadjuvant phase III study NeoALTTO and correlated these variables with pathologic complete response (pCR) and progression-free survival (PFS) following lapatinib (L), trastuzumab (T), or the combination of both agents (L+T).

RESULTS

A positive correlation between p95HER2 and HER2 levels was found in the 274 cases (60%) in which quantification of both markers was possible. High levels of these markers were predictive for pCR, especially in the hormone receptor (HR)-positive subset of patients. High HER2 expression was associated with increased pCR rate upon L+T irrespective of the HR status. To examine whether the levels of either p95HER2 or HER2 could predict for PFS in patients treated with lapatinib, trastuzumab or L+T, we fit to the PFS data in Cox models containing log2(p95HER2) or log2(HER2). Both variables correlated with longer PFS.

CONCLUSIONS

Increasing HER2 protein expression correlated with increased benefit of adding lapatinib to trastuzumab. HER2 expression is a stronger predictor of pCR and PFS than p95HER2 for response to lapatinib, trastuzumab and, more significantly, L+T.

Effect of p95HER2/611CTF on the response to trastuzumab and chemotherapy

Human epidermal growth factor receptor 2 (HER2)-positive breast cancers are currently treated with trastuzumab, an anti-HER2 antibody. About 30% of these tumors express a group of HER2 fragments collectively known as p95HER2. Our previous work indicated that p95HER2-positive tumors are resistant to trastuzumab monotherapy. However, recent results showed that tumors expressing the most active of these fragments, p95HER2/611CTF, respond to trastuzumab plus chemotherapy. To clarify this discrepancy, we analyzed the response to chemotherapy of cell lines transfected with p95HER2/611CTF and patient-derived xenografts (n = 7 mice per group) with different levels of the fragment. All statistical tests were two-sided. p95HER2/611CTF-negative and positive tumors showed different responses to various chemotherapeutic agents, which are particularly effective on p95HER2/611CTF-positive cells. Furthermore, chemotherapy sensitizes p95HER2/611CTF-positive patient-derived xenograft tumors to trastuzumab (mean tumor volume, trastuzumab alone: 906 mm(3), 95% confidence interval = 1274 to 538 mm(3); trastuzumab+doxorubicin: 259 mm(3), 95% confidence interval = 387 to 131 mm(3); P < .001). This sensitization may be related to HER2 stabilization induced by chemotherapy in p95HER2/611CTF-positive cells.

Neoadjuvant therapy of early stage human epidermal growth factor receptor 2 positive breast cancer: latest evidence and clinical implications

Neoadjuvant therapy in human epidermal growth factor receptor 2 (HER2)-positive breast cancer is exactly the paradigm of targeted therapy and a suitable setting to develop and test rapidly novel therapies in early stages. Moreover, neoadjuvant approaches provide a significant source of tumour tissue to identify molecular heterogeneity and potential predictive biomarkers of response. The addition of trastuzumab to primary chemotherapy revolutionized the treatment of this tumour subtype, increasing pathological complete response rate (pCR) that, even with its limitations, has also been shown to be an early marker of survival in HER2-positive disease. HER2-positive breast cancer is a biological heterogeneous disease with different characteristics and clinical outcomes. Multiple promising anti-HER2 drugs with nonoverlapping mechanisms of action have recently been developed. Combined administration of two different HER2-targeted agents, that is, trastuzumab with lapatinib or pertuzumab, and primary chemotherapy shows enhanced antitumour activity, with an increase in pCR to values never reached in the past. Moreover, results of recent studies show that the combination of targeted therapy alone (dual HER2 blockade with or without endocrine therapy) also has activity in a substantial percentage of patients, eradicating HER2-positive tumours without chemotherapy and with a favourable toxicity profile. It is still necessary to be able to select the appropriate group of patients who can avoid chemotherapy (approximately 25%), and to establish robust predictive biomarkers of response or resistance to the anti-HER2 approach. Neoadjuvant therapy represents an enormous step forward in HER2-positive breast cancer. The results of the most relevant neoadjuvant studies and latest evidence are described in this review, though new questions have emerged.

Quantitative measurements of tumoral p95HER2 protein expression in metastatic breast cancer patients treated with trastuzumab: independent validation of the p95HER2 clinical cutoff

PURPOSE

P95HER2 (p95) is a truncated form of the HER2, which lacks the trastuzumab-binding site and contains a hyperactive kinase domain. Previously, an optimal clinical cutoff of p95 expression for progression-free survival (PFS) and overall survival (OS) was defined using a quantitative VeraTag assay (Monogram Biosciences) in a training set of trastuzumab-treated metastatic breast cancer (MBC) patients.

EXPERIMENTAL DESIGN

In the current study, the predictive value of the p95 VeraTag assay cutoff established in the training set was retrospectively validated for PFS and OS in an independent series of 240 trastuzumab-treated MBC patients from multiple institutions.

RESULTS

In the subset of 190 tumors assessed as HER2-total (H2T)-positive using the quantitative HERmark assay (Monogram Biosciences), p95 VeraTag values above the predefined cutoff correlated with shorter PFS (HR = 1.43; P = 0.039) and shorter OS (HR = 1.94; P = 0.0055) where both outcomes were stratified by hormone receptor status and tumor grade. High p95 expression correlated with shorter PFS (HR = 2.41; P = 0.0003) and OS (HR = 2.57; P = 0.0025) in the hormone receptor-positive subgroup of patients (N = 78), but not in the hormone receptor-negative group. In contrast with the quantitative p95 VeraTag measurements, p95 immunohistochemical expression using the same antibody was not significantly correlated with outcomes.

CONCLUSIONS

The consistency in the p95 VeraTag cutoff across different cohorts of patients with MBC treated with trastuzumab justifies additional studies using blinded analyses in larger series of patients.

Clinical significance of p95HER2 overexpression, PTEN loss and PI3K expression in p185HER2-positive metastatic breast cancer patients treated with trastuzumab-based therapies

Background:

Overexpression of p185HER2 is an established poor prognostic factor in breast cancer, portending an aggressive course and potential for early metastasis. On the other hand, monoclonal antibody trastuzumab is widely used in the clinic to target this overexpressed oncogene. Unfortunately, ∼30–40% of all patients overexpressing HER2 respond to trastuzumab, warranting further research regarding the structure and additional modulation of the receptor. In this study, we aimed to investigate the response to trastuzumab in terms of the potential roles of several oncogenic pathways (phosphatase and tensin homologue (PTEN) and phosphatidylinositol 3-kinase (PI3K)) and a truncated receptor protein, p95HER2, retrospectively.

Materials and methods:

Paraffin-embedded primary tumour tissues of 100 HER2-positive metastatic breast cancer patients who received trastuzumab with combination cytotoxic chemotherapy were analysed with immunohistochemical method for p95HER2, p85 (PI3K) and PTEN. Relationship between variables were tested via χ², Fischer's exact test and Mann–Whitney U tests, wherever appropriate. Progression-free survival (PFS) and overall survival (OS) periods were calculated with Kaplan–Meier method and survival curves of subgroups were compared with log-rank test.

Results:

Percentage of patients was found to be 33%, 57% and 42% positive for p95 expression, PTEN and PI3K, respectively. p95-expressing tumours had statistically lower response rates for trastuzumab than tumours not expressing p95 (P=0.001). On the contrary, PTEN-expressing tumours had statistically higher response rates for trastuzumab than tumours not expressing PTEN (P=0.012). PI3K expression had no significant effect on trastuzumab response. Median PFS for p95-expressing and not expressing tumours were 8 months (95% CI, 2.5–13.4 months) and 22 months (95% CI, 9.9–34 months), respectively (P=0.0001). Median PFS for PTEN-expressing and not expressing tumours were 15.3 months (95% CI, 12.6–34 months) and 12.1 months (95% CI, 7.9–16.2 months), respectively (P=0.04). Median OS for p95-expressing and not expressing tumours were 24 months (95% CI, 8.3–40.4 months) and 29.1 months (95% CI, 8.6–43.2 months), respectively (P=0.045). Median OS for PTEN-expressing and not expressing tumours were 25.1 months (95% CI, 7.5–40.1 months) and 26.8 months (95% CI, 8.1–42 months), respectively, which was not statistically significant (P=0.5). Level of PI3K expression had no effect on PFS and OS in our patient population. Presence of visceral metastases HR=2.38 ((95% CI, 1.2–4.5), P=0.009), p95 expression HR=2.1 ((95% CI, 1.1–3.7), P=0.03) and response to trastuzumab HR=2.2 ((95% CI, 1.18–4.47), P=0.014) are identified as factors independently affecting PFS. Response to trastuzumab HR=1.7 ((95% CI, 1.14–3.47), P=0.013) was identified as the single parameter influencing survival by Cox regression analysis.

Conclusions:

Presence of p95 predicted a poorer response to trastuzumab treatment, shorter PFS and OS in our HER2-positive metastatic breast cancer cohort. In addition, loss of PTEN predicted a poorer response to trastuzumab treatment and shorter PFS but not OS. We could not find an effect of PI3K expression on the above-mentioned parameters.

Neoadjuvant treatment of HER2 and hormone-receptor positive breast cancer - moving beyond pathological complete response

Pathologic complete response (pCR) was noted to be prognostic in all but hormone receptor-positive (HR) breast cancer cases even when HER2 is overexpressed. Evocative data suggest that HER2-positive breast cancer patients are a heterogeneous population and a subset of HER2-positive and HR-positive tumors biologically behave more like HER2-negative. Identification and targeted monitoring of these patients is crucial to consolidate data aiming to optimize combination treatment with new agents, thereby avoiding overtreatment with chemotherapy. The questions surrounding HER2-positive and HR-positive breast cancer patients treatment as well as the potential direction towards development of surrogate markers alternative to pCR are discussed.

A phase II study of ixabepilone and trastuzumab for metastatic HER2-positive breast cancer

BACKGROUND

A multicenter NCI-sponsored phase II study was conducted to analyze the safety and efficacy of the combination of ixabepilone with trastuzumab in patients with metastatic HER2-positive breast cancer.

PATIENTS AND METHODS

Two cohorts were enrolled: cohort 1 had received no prior chemotherapy or trastuzumab for metastatic disease and cohort 2 had received 1-2 prior trastuzumab-containing regimens for metastatic disease. Patients in both cohorts received ixabepilone 40 mg/m(2) as a 3-h infusion and trastuzumab on day 1 of a 21-day cycle. Tumor biomarkers that may predict response to trastuzumab were explored.

RESULTS

Thirty-nine women entered the study with 15 patients in cohort 1 and 24 patients in cohort 2. Across both cohorts, the overall RR was 44%, with a clinical benefit rate (CR + PR + SD for at least 24 weeks) of 56%. Treatment-related toxic effects included neuropathy (grade ≥2, 56%), leukopenia (grade ≥2, 26%), myalgias (grade ≥2, 21%), neutropenia (grade ≥2, 23%), and anemia (grade ≥2, 18%).

CONCLUSIONS

This represents the first study of the combination of ixabepilone with trastuzumab for the treatment of metastatic HER2-positive breast cancer. These results suggest that the combination has encouraging activity as first and subsequent line therapy for metastatic breast cancer.

A novel proteomics-based clinical diagnostics technology identifies heterogeneity in activated signaling pathways in gastric cancers

Purpose

The aim of this study was to utilize the proteomics-based Collaborative Enzyme Enhanced Reactive (CEER) immunoassay to investigate protein tyrosine phosphorylations as diagnostic markers in gastric cancers (GCs).

Experimental Design

Protein lysates from fresh-frozen 434 advanced stage GCs were analyzed for phosphorylation of HER1, HER2, p95HER2, HER3, cMET, IGF1R and PI3K. The pathway activation patterns were segregated based on the tumor HER2 status. Hierarchical clustering was utilized to determine pathway coactivations in GCs. Prognostic value of pathway activation patterns was determined by correlating disease-free survival times of the various GC subgroups using Kaplan-Meier survival analysis. CEER was also used to determine the presence of tyrosine phosphorylated signaling cascades in circulating tumor cells (CTCs) and ascites tumor cells (ATCs).

Results

Utilizing a novel diagnostics immunoassay, CEER, we demonstrate the presence of p95HER2 and concomitantly activated signaling pathways in GC tumor tissues, CTCs and ATCs isolated from GC patients for the first time. p95HER2 is expressed in ∼77% of HER2(+) GCs. Approximately 54% of GCs have an activated HER1, HER2, HER3, cMET or IGF1R and demonstrate a poorer prognosis than those where these receptor tyrosine kinases (RTKs) are not activated. Hierarchical clustering of RTKs reveals co-clustering of phosphorylated HER1:cMET, HER2:HER3 and IGF1R-PI3K. Coactivation of HER1 with cMET renders GCs with a shorter disease-free survival as compared to only cMET activated GCs.

Conclusions

Our study highlights the utility of a novel companion diagnostics technology, CEER that has strong implications for drug development and therapeutic monitoring. CEER is used to provide an increased understanding of activated signaling pathways in advanced GCs that can significantly improve their clinical management through accurate patient selection for targeted therapeutics.

Evaluation of PTEN loss and PIK3CA mutations and their correlation with efficacy of trastuzumab treatment in HER2-positive metastatic breast cancer: A retrospective study (KBC-SG 1001)

Trastuzumab (T) has contributed to improving the prognosis of human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Although some patients have been unresponsive or resistant to T. Loss of phosphatase and tensin homolog (PTEN) deleted on chromosome 10, PIK3CA mutation and p95HER2 expression have been reported to potentially be responsible for the poor response to T. This is a small-scale pilot study to be followed by a large-scale investigation examining the association between the biomarkers and clinical response. Based on the response to T, patients were divided into 3 groups in terms of progression-free survival (PFS): PFS >8 months (group A, n=15), 3-8 months (group B, n=7) and PFS <3 months (group C, n=11). PTEN protein expression was detected by immunohistochemistry and PIK3CA mutation by direct sequencing. The median age was 61, 60 and 47 years in groups A, B and C, respectively, with statistically significant differences among the groups. No additional patient background factors differed between the groups. A decreased PTEN expression (H score, <100) was observed in 33.3 and 72.7% of patients in groups A and C, respectively. PTEN loss was slightly correlated with poor response to T. PIK3CA mutation frequency in exons 9/20 was 33.3% in group A and 27.3% in group C, with no significant correlation between PIK3CA mutation and clinical response. In this small-scale pilot study, a weak correlation was demonstrated between PTEN loss and poor response to T. This potential correlation is likely to be confirmed in the planned large-scale study, while the association of PIK3CA mutation and p95HER2 expression with poor response to T also requires examination.

Spontaneous and pronase-induced HER2 truncation increases the trastuzumab binding capacity of breast cancer tissues and cell lines

A subgroup of HER2-overexpressing breast tumours co-expresses p95(HER2), a truncated HER2 receptor that retains a functional HER2 kinase domain but lacks the extracellular domain, thus impairing trastuzumab binding. We evaluated p95(HER2) expression in 99 frozen breast carcinoma samples by western blot analysis. The HER2-positive cell line BT474 treated with pervanadate or pronase was used as a positive control for p95(HER2) expression. Immunohistochemistry was performed on parallel formalin-fixed, paraffin-embedded sections of the same case series using antibodies directed against either the intra- or extra-cellular binding domain of HER2. In particular, biotinylated trastuzumab (BiotHER) was used to evaluate the binding capacity of the humanized antibody. To avoid a subjective evaluation of the score values and the percentage of immunostained cells, the slides were scanned and automatically analysed. The number of cases with HER2 overexpression (score 3+) and HER2 gene amplification was higher in the p185(HER2)-positive/p95(HER2)-positive samples than in the p185(HER2)-positive/p95(HER2)-negative group. Automated analysis confirmed a significantly higher percentage of 3+ scored cells in p95(HER2)-positive cases. Conversely, the percentage of 2+ scored cells was higher inp95(HER2)-negative cases. The status of the HER2 extracellular domain was then studied using flow cytometry on BT474 cells after pronase enzymatic digestion using trastuzumab and pertuzumab, while the presence of HER2-HER3 dimers was studied using a proximity-ligation assay. In vitro experiments showed that short-term pronase digestion of BT474 cells produced two HER2 fragments (of 95 and 150 kDa, detectable in tissue specimens as well), increased the binding affinity of trastuzumab, reduced the rate of HER2-HER3 dimers, and did not interfere with pertuzumab-binding capacity. In conclusion, the presence of p95(HER2 as detected by western blot analysis does not compromise the immunohistochemical detection of HER2. Our data suggest that a reduction of the receptor steric hindrance as induced by enzymatic shedding may facilitate the binding capacity of trastuzumab.

Neoadjuvant chemotherapy in breast cancer-insights from the German experience

New insights into neoadjuvant treatment of breast cancer have shown that the prognostic value of pathological complete response has to be rated differently according to subtype. Whereas in triple-negative, HER2-positive (non-luminal) and luminal B (HER2-negative) patients with a pCR after neoadjuvant chemotherapy show a significantly better outcome than patients without a pCR, this prognostic impact cannot be seen in patients with luminal A or luminal B (HER2-positive) tumors. Patients can therefore only avoid an initially high-risk prognosis if they have a pCR of these first mentioned subtypes. For patients with those tumors or with high Ki-67 levels in residual disease, new treatment options have to be found. Contrarily, response-guided chemotherapy, i.e., changing the regimen in case of no early response or intensification in case of early response, showed significant survival advantages only in the latter group. Strategies are currently being developed on how locoregional treatment can be reduced in patients with a pathological complete response. These aim to reduce the extent of surgery or even avoid surgery completely.

Advances in first-line treatment for patients with HER-2+ metastatic breast cancer

BACKGROUND

The prognosis for breast cancer patients overexpressing human epidermal growth factor receptor (HER)-2 has changed with anti-HER-2-targeted therapy. Although anti-HER-2 therapy with trastuzumab and chemotherapy is the standard first-line treatment, the best therapeutic regimen has yet to be defined, and new strategies are evolving.

METHODS

A literature review of well-established and recently published trials, reviews, and ongoing clinical trials addressing first-line treatment for HER-2(+) metastatic breast cancer patients was performed.

RESULTS

Taxanes are the agents most commonly used in combination with trastuzumab, but other chemotherapy drugs, such as anthracyclines, vinorelbine, and gemcitabine and triple-combination therapies including platinum compounds, capecitabine, and taxanes have been studied. The combination of aromatase inhibitors with anti-HER-2 therapies is a new therapeutic option for some patients who coexpress HER-2 and hormone receptors, although its activity observed in randomized clinical trials seems to be inferior to that of chemotherapy plus anti-HER-2 therapies. In addition, new anti-HER-2 therapies have shown activity in HER-2(+) tumors, both alone and in combination with trastuzumab.

CONCLUSIONS

Trastuzumab plus chemotherapy is the current standard of care for the upfront treatment of HER-2(+) breast cancer patients, though other anti-HER-2-targeting agents may appear as new standards in the upcoming years.