Individualizing Curative-Intent Therapy in HER2-Positive Early-Stage Breast Cancer

OPINION STATEMENT

Human epidermal growth factor receptor 2-positive (HER2+) breast cancers have been historically considered an aggressive entity with high rates of recurrence and poor survival. However, during the last 20 years, there has been a dramatic change in prognosis due to the incorporation of different anti-HER2 therapies into the neo/adjuvant chemotherapy backbone. Neoadjuvant dual blockade with trastuzumab and pertuzumab has become the standard of care for women with stage II and III HER2+ breast cancer. Trastuzumab emtansine (T-DM1) has been shown to improve outcomes if pathological complete response (pCR) is not achieved, and adjuvant extended therapy with neratinib has increased disease-free survival (DFS) and may have an impact in central nervous system (CNS) recurrences. However, these agents are both toxic for individual patients and costly for the overall healthcare system, and there are still patients that experience recurrence despite therapy improvements. At the same time, it has been shown that some patients with early-stage HER2+ breast cancer can be effectively treated with less intensive systemic therapy, using only taxane and trastuzumab, or that the chemotherapy backbone can be omitted completely. The current challenge is to properly identify which patients can receive a de-intensified regimen and which need new intensification strategies. Tumor size, nodal status, and pCR achievement after neoadjuvant treatment are well-known risk factors that can aid in making clinical decisions, but they do not accurately predict all patient outcomes. Various biomarkers have been proposed to better characterize the clinical and biological heterogeneity of HER2+ breast cancer. Immune infiltration, intrinsic subtype, intratumoral heterogeneity, and dynamic changes during treatment have been described as important prognostic and/or predictive features. The integration of all these factors will be key in the proper identification of the true risk, and individualized treatment strategy, for each patient.

Evolving standards of care and new challenges in the management of HER2-positive breast cancer

The management of human epidermal growth factor receptor (HER2)-positive breast cancer (BC) has rapidly evolved over the last 20 years. Major advances have led to US Food and Drug Administration approval of 7 HER2-targeted therapies for the treatment of early-stage and/or advanced-stage disease. Although oncologic outcomes continue to improve, most patients with advanced HER2-positive BC ultimately die of their disease because of primary or acquired resistance to therapy, and patients with HER2-positive early BC who have residual invasive disease after preoperative systemic therapy are at a higher risk of distant recurrence and death. The concept of treatment de-escalation and escalation is increasingly important to optimally tailor therapy for patients with HER2-positive BC and is a major focus of the current review. Research efforts in this regard are discussed as well as updates regarding the evolving standard of care in the (neo)adjuvant and metastatic settings, including the use of novel combination therapies. The authors also briefly discuss ongoing challenges in the management of HER2-positive BC (eg, intrinsic vs acquired drug resistance, the identification of predictive biomarkers, the integration of imaging techniques to guide clinical practice), and the treatment of HER2-positive brain metastases. Research aimed at superseding these challenges will be imperative to ensure continued progress in the management of HER2-positive BC going forward.

Long-Term Survival Analysis of Adjuvant Chemotherapy with or without Trastuzumab in Patients with T1, Node-Negative HER2-Positive Breast Cancer

PURPOSE

Adjuvant therapy for small, node-negative HER2-positive breast cancer (HER2⁺ BC) is controversial. We aimed to identify the subgroup that would benefit most from adjuvant chemotherapy and trastuzumab.

EXPERIMENTAL DESIGN

We reviewed records of patients with pT1N0M0 HER2⁺ BC treated at our institution from January 1, 1998, through October 31, 2009. We compared three groups: A, no adjuvant chemotherapy; B, adjuvant chemotherapy only; and C, adjuvant chemotherapy with trastuzumab. We evaluated disease-free survival (DFS), overall survival (OS), distant recurrence-free survival (DRFS), and breast cancer-specific survival (BCSS) in each group.

RESULTS

We reviewed 587 consecutive patients with a median follow-up of 123.0 months. The 10-year DFS rate was 81.0%, 65.4%, and 97.3% in groups A, B, and C, respectively (P < 0.001). The restricted mean survival time ratio did not differ between groups A and B [ratio = 0.982; 95% confidence interval (CI), 0.930-1.036; P = 0.498). Cox regression showed that adjuvant chemotherapy with trastuzumab was associated with better DFS compared with no adjuvant chemotherapy [hazard ratio (HR), 0.071; 95% CI, 0.025-0.204; P < 0.001). Larger tumor size was associated with short DFS (HR, 2.384; 95% CI, 1.549-3.056; P < 0.001); improvements in DFS, OS, DRFS, and BCSS were observed with adjuvant chemotherapy plus trastuzumab in patients with tumors ≥0.8-cm diameter. Receiving adjuvant chemotherapy with trastuzumab was not associated with improved DFS, OS, or DRFS for tumors <0.8 cm.

CONCLUSIONS

Adjuvant chemotherapy plus trastuzumab should be recommended for patients with pT1N0M0 HER2⁺ BC ≥0.8 cm in diameter; adjuvant therapy may not be necessary for tumors <0.8 cm.

Current Development of Monoclonal Antibodies in Cancer Therapy

Exploiting the unique specificity of monoclonal antibodies has revolutionized the treatment and diagnosis of haematological and solid organ malignancies; bringing benefit to millions of patients over the past decades. Recent achievements include conjugating antibodies with toxic payloads resulting in superior efficacy and/or reduced toxicity, development of molecular imaging techniques targeting specific antigens for use as predictive and prognostic biomarkers, the development of novel bi- and tri-specific antibodies to enhance therapeutic benefit and abrogate resistance and the success of immunotherapy agents. In this chapter, we review an overview of antibody structure and function relevant to cancer therapy and provide an overview of pivotal clinical trials which have led to regulatory approval of monoclonal antibodies in cancer treatment. We further discuss resistance mechanisms and the unique side effects of each class of antibody and provide an overview of emerging therapeutic agents.

Intratumor lactate levels reflect HER2 addiction status in HER2-positive breast cancer

Despite different molecular tumor profiles indicate that human epidermal growth factor receptor 2 (HER2) messenger RNA (mRNA) levels mirror HER2 addiction and trastuzumab benefit in HER2-positive breast cancer (BC), the identification of noninvasive clinical predictors of trastuzumab sensitivity remains an unmet clinical need. In the current study, we investigated whether intratumor lactate levels reflect HER2 addiction and, in turn, trastuzumab susceptibility. Accordingly, the gene expression profiles of transgenic murine BC cell lines expressing the human d16HER2 variant (HER2-addicted) or human full-length HER2 (WTHER2; HER2-nonaddicted) revealed a significant enrichment of glycolysis-related gene pathways in HER2-addicted cells. We studied the metabolic content of 22 human HER2-positive BC by quantitative nuclear magnetic resonance spectroscopy and found that those cases with higher lactate levels were characterized by higher HER2 transcript levels. Moreover, gene expression analyses of HER2-positive BC samples from a TCGA data set revealed a significant enrichment in glycolysis-related pathways in high/HER2-addicted tumors. These data were confirmed by metabolic analyses of human HER2-positive BC cell lines with high or low HER2 transcript levels, which revealed significantly more active glycolytic metabolism in high HER2 transcript than in low HER2 transcript cells. Overall, our results provide evidence for noninvasive intratumor lactate detection as a potential metabolic biomarker of HER2 addiction and trastuzumab response suggesting the possibility to use in vivo imaging to assess lactate levels and, in turn, select HER2-positive BC patients who are more likely to benefit from anti-HER2 treatments.