[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.