Optimizing treatment of HER2-positive metastatic breast cancer

Capecitabine–docetaxel combination treatment

Metastatic breast cancer develops in approximately 50% of women diagnosed with breast cancer. The optimal treatment for patients with metastatic breast cancer has yet to be defined, owing to the heterogeneity of this group and the available agents. Patients with metastatic breast cancer often receive single-agent treatment in sequence as it is unclear whether combination therapy with cytotoxic drugs offers an overall disease-free survival benefit and single agents may offer less toxicity. The advantages of combination cytotoxic therapies have included higher response rates. However, such trials have not stratified on rapidity of disease progression or on tumor bulk. In previous studies, docetaxel is one of the few cytotoxic agents to demonstrate a survival benefit in anthracycline-resistant patients and thus it has become a vital component of cytotoxic therapy. Capecitabine is also an important oral drug and has demonstrated activity in patients pretreated with anthracyclines and taxanes. Recent preclinical and clinical trials of this combination have demonstrated an increased time to tumor progression and overall survival benefit. Paclitaxel combined with gemcitabine has been compared with docetaxel plus capecitabine, with similar response rates and survival benefits. As patients on these trials have not received uniform crossover to the other active agent, whether or not the combination therapy offers an advantage for the entire cohort of metastatic patients or may be indicated for specific subgroups remains uncertain. Combination treatments may be preferable to sequential therapy for patients requiring urgent reduction in their tumor burden. Combinations of cytotoxic agents in combination with biological agents are currently being defined.

Clinical proteomics: from biomarker discovery and cell signaling profiles to individualized personal therapy

The discovery of new highly sensitive and specific biomarkers for early disease detection and risk stratification coupled with the development of personalized "designer" therapies holds the key to future treatment of complex diseases such as cancer. Mounting evidence confirms that the low molecular weight (LMW) range of the circulatory proteome contains a rich source of information that may be able to detect early stage disease and stratify risk. Current mass spectrometry (MS) platforms can generate a rapid and high resolution portrait of the LMW proteome. Emerging novel nanotechnology strategies to amplify and harvest these LMW biomarkers in vivo or ex vivo will greatly enhance our ability to discover and characterize molecules for early disease detection, subclassification and prognostic capability of current proteomics modalities. Ultimately genetic mutations giving rise to disease are played out and manifested on a protein level, involving derangements in protein function and information flow within diseased cells and the interconnected tissue microenvironment. Newly developed highly sensitive, specific and linearly dynamic reverse phase protein microarray systems are now able to generate circuit maps of information flow through phosphoprotein networks of pure populations of microdissected tumor cells obtained from patient biopsies. We postulate that this type of enabling technology will provide the foundation for the development of individualized combinatorial therapies of molecular inhibitors to target tumor-specific deranged pathways regulating key biologic processes including proliferation, differentiation, apoptosis, immunity and metastasis. Hence future therapies will be tailored to the specific deranged molecular circuitry of an individual patient's disease. The successful transition of these groundbreaking proteomic technologies from research tools to integrated clinical diagnostic platforms will require ongoing continued development, and optimization with rigorous standardization development and quality control procedures.

Pre-operative systemic (neo-adjuvant) therapy with trastuzumab and docetaxel for HER2-overexpressing stage II or III breast cancer: results of a multicenter phase II trial

BACKGROUND

Trastuzumab plus chemotherapy has become the standard of care for women with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. Trastuzumab-based pre-operative systemic (neo-adjuvant) therapy (PST) also appears promising, warranting further investigation.

PATIENTS AND METHODS

Patients with HER2-positive, stage II/III non-inflammatory, operable breast cancer requiring a mastectomy (but who wished to conserve the breast) received weekly trastuzumab and 3-weekly docetaxel for six cycles before surgery. The primary end point was pathological complete response (pCR) rate, determined from surgical specimens.

RESULTS

Thirty-three patients were enrolled. The majority (79%) had T2 tumors, with 42% being N1/2. Twenty-nine patients completed six cycles of therapy and one patient withdrew prematurely due to progressive disease. A complete or partial objective clinical response was seen in 96% (73% and 23%, respectively) of patients. Surgery was performed in 30 patients, breast conserving in 23 (77%). In an intention-to-treat analysis, tumor and nodal pCR was seen in 14 (47%) patients. Treatment was generally well tolerated. Grade 3/4 neutropenia occurred in 85% of patients while febrile neutropenia was encountered in 18%. Only three patients withdrew prematurely due to toxicity. No symptomatic cardiac dysfunction was reported.

CONCLUSIONS

PST with trastuzumab plus docetaxel achieved promising efficacy, with a high pCR rate and good tolerability, in women with stage II or III HER2-positive breast cancer.

Future options with trastuzumab for primary systemic and adjuvant therapy

HER2 positivity can be detected early in breast cancer development and is associated with a poor outcome. Primary systemic therapy with trastuzumab (Herceptin; F. Hoffmann-La Roche, Basel, Switzerland) in combination with taxanes and other cytotoxic agents has been studied in phase II clinical trials in women with HER2-positive breast cancer. These combinations have achieved pathologic complete response rates of 12% to 42% and clinical complete response rates of 30% to 67%. These results compare favorably with those of primary systemic therapy using standard combinations in patients with unselected (HER2-positive or -negative) breast cancer. Consequently, larger studies are in progress in which trastuzumab is administered before surgery in combination with chemotherapy. Trastuzumab is continued as monotherapy afterward to complete 1 year of treatment or until disease progression. These studies aim to provide further proof of the clinical benefits associated with trastuzumab as primary systemic therapy. They will also investigate the molecular determinants of sensitivity and resistance. In addition, four major randomized trials, in more than 13,500 patients, are investigating the impact of adding trastuzumab to standard adjuvant therapy. Planned interim cardiac safety analyses have been passed without concerns. Recruitment to these studies has either recently been completed or continues as planned. Together, this extensive program, which includes analysis of predictive molecular and pathologic makers, will establish the efficacy, safety, and role of trastuzumab in early breast cancer.

Maximizing clinical benefit with trastuzumab

To optimize patient management in breast cancer a number of factors are considered, including hormone receptor and HER2 status. A feasible approach for women with less aggressive, estrogen receptor/HER2-positive metastatic breast cancer is to consider trastuzumab (Herceptin; F. Hoffmann-La Roche, Basel, Switzerland) combined with endocrine therapy. Randomized clinical trials are ongoing to assess the combination of trastuzumab with aromatase inhibitors. In patients with aggressive HER2-positive metastatic breast cancer, trastuzumab/chemotherapy combination regimens are warranted. When administered first line in combination with a taxane, trastuzumab improves all clinical outcome parameters, including survival, in such patients. Trastuzumab adds little to the toxicity profile of taxanes, and trastuzumab combination therapy is associated with improvements in quality of life when compared with chemotherapy alone. There is encouraging evidence of improved efficacy when trastuzumab is combined with other cytotoxic agents with proven single-agent activity in breast cancer, including capecitabine (Xeloda; F. Hoffmann-La Roche), gemcitabine, and vinorelbine. Trastuzumab is also being investigated as part of triplet drug regimens. Trastuzumab has good single-agent activity in first-line therapy. This is of relevance to women with HER2-positive disease who are not suitable for, or do not wish to receive, cytotoxic chemotherapy. The benefits noted with trastuzumab-containing regimens were documented in clinical trials where trastuzumab was given until disease progression. A further rationale exists to continue trastuzumab beyond progression. Data from retrospective reviews indicate that this strategy is feasible.