[Management of metastatic HER2-positive breast cancer: present and future]

Parameterization of a disease progression simulation model for sequentially treated metastatic human epidermal growth factor receptor 2 positive breast cancer patients

Background The objective of this study is twofold: 1) to propose a simulation model for HER2+ metastatic breast cancer (mBC) which could further be used to assess the overall cost-effectiveness of the treatment sequences that would maximize survival of patients, and 2) to estimate transitional probabilities between treatment lines required to parameterize the simulation model, in the absence of individual patient data (IPD). Methods Individual patient data (IPD) were reconstructed for treatment lines composing four treatment sequences. Parametric models were tested to select the model that best fits the IPD. The transitional probability equations, used for disease progression modeling, were obtained by substituting the parameters of the general equation for transitional probabilities by the parameters estimated from fitted distributions. Results The log-logistic model best fitted the reconstructed data for progression-free and overall survival curves for each line of treatment. The shapes and scales of the log-logistic models were used to develop the transitional probability equations for the HER2+ mBC simulation model.

KEY LIMITATIONS

The estimation of the transitional probabilities depends heavily on the accuracy of the IPD reconstruction. Nonetheless, analytical and graphical tests can be performed to check the face validity of the reconstructed data. Additionally, sensitivity analyses can be conducted to test the impact of uncertainty surrounding the estimated parameters defining equations for transitional probabilities. Conclusion The results of this study can be used as input in model-based economic evaluations of sequential therapy for HER2+ mBC.

[Targeted based therapies in metastatic breast cancer: future evolution]

Research on molecular alteration process mechanisms leading to cancerogenesis permitted the elaboration of many targeted therapies. Some therapeutic classes appeared recently and are currently being tested, including HER-2 dimerization inhibitors. However, most of these therapies are mostly ineffective with monotherapy. Clinical trials are ongoing, testing their efficiency in association with other molecules of the therapeutic arsenal which is available in oncology. Nevertheless, breast cancer remains a pathology life-threatening, most of the time. Within this review will be introduced the most efficient of these targeted therapies, including their eventual association with other cytotoxic molecules.

[Leptomeningeal meningitis related to breast cancer overexpressing HER2: is there a place for a more specific treatment?]

Leptomeningeal metastases are very commonly associated with breast cancer. The prognosis is very poor in the short term with an overall median survival less than 6 months. Based on pragmatic and historical considerations intrathecal chemotherapy (IT) are considered to be the adequate treatment. However overall results are disappointing. Despite specific and symptomatic treatment, improvement in survival and quality of life remains very modest, highlighting the importance for ongoing research for developing new molecules or on improving the use a better use of those available today. The incidence of leptomeningeal metastases is particularly marked in cases of overexpression of HER2. The main hypothesis is there may be a better control of extra-cerebral localisations with trastuzumab therefore intra-cerebral recurrences may be encountered preferentially as they are not reached by this high molecular weight monoclonal antibody (148  kD). Analyses performed in the cerebrospinal fluid following intravenous trastuzumab showed extremely low levels of the antibody and support the hypothesis that leptomeningeal metastasis of HER2-overexpressing breast carcinoma remain potentially sensitive to HER2-type receptor inhibition by a target agent under the condition of by-passing the meningeal blood brain barrier. Intra-ventricular or IT administered with trastuzumab would reach high loco-regional therapeutic concentrations in the cerebro-meningeal without risk for normal non-expressing HER2 leptomeningeal tissue. This strategy has been successfully tested on several animal models. A limited number of administrations in humans have been described in the literature, with weekly doses up to 100  mg. No specific toxicity has been described and some data suggest a potential benefit in survival despite the real difficulties for adequate interpretations. Furthermore, a multicentric phase I-II clinical trial, of which the Curie institute is the sponsor and investigating the intra-thecal administration and the efficacy of the trastuzumab will begin very soon. More studies are needed to measure the exact impact of small molecule inhibitors of tyrosine kinase on the leptomeningeal localizations.