Background
Patients with human epidermal growth factor receptor 2-positive (HER2-positive) cancers have a high incidence of central nervous system (CNS) spread, but unfortunately systemic trastuzumab which targets the HER2 receptor has little CNS penetration. The purpose of this study was to determine the maximum tolerated dose of intrathecal trastuzumab and its efficacy in patients with HER2-positive LMD.
Methods
This multicenter study enrolled 34 LMD patients in a combined Phase I/II study in treating patients with intrathecal trastuzumab. Any HER2-positive histology was allowed in the Phase I; the Phase II was limited to HER2-positive breast cancer.
Results
Intrathecal trastuzumab was well tolerated, with one dose limiting toxicity of grade 4 (arachnoiditis) occurring at the 80 mg twice weekly dose. The recommended Phase II dose was 80 mg intrathecally twice weekly. Twenty-six patients at dose level 80mg were included in evaluation for efficacy: partial response was seen in 5 (19.2%) patients, stable disease was observed in 13 (50.0%), and 8 (30.8%) of the patients had progressive disease. Median overall survival (OS) for Phase 2 dose treated patients was 8.3 months (95% CI 5.2 to 19.6). The Phase II HER2-positive breast cancer patients median OS was 10.5 months (95% CI 5.2 to 20.9). Pharmacokinetic (PK) studies were limited in the setting of concurrent systemic trastuzumab administration, however, did show stable CSF concentrations with repeated dosing suggest that trastuzumab does not accumulate in the CSF in toxic concentrations.
Conclusion
This study suggests promise for potentially improved outcomes of HER-positive LMD patients when treated with intrathecal trastuzumab while remaining safe and well-tolerated for patients.
The novel anti-mitotic based tumor treating fields (TTFields) is FDA approved for recurrent glioblastoma. Recently the phase III upfront trial combining the Novo TTF-100A device, called Optune, with temozolomide following concurrent radiation therapy and chemotherapy, demonstrated improvement in survival. Wider use of this novel therapy is expected. The most common adverse event is dermatologic, which dominates compared to the next most frequently observed adverse event of headaches, the incidence of which was even in both arms in the phase III registration trial for recurrent glioblastoma. Our case review outlines the presentation, treatment, and outcome of representative patients using TTFields. In summary, preventative strategies to inform and educate patients and operators can prevent many of these dermatological events. Skin toxicity in the setting of concurrent use of TTFields with other therapies such as bevacizumab is an unknown and will need to be closely followed.
The microenvironment of an IDH1mut glioma is likely being exposed to high concentrations of D2HG, in the low millimolar range. This has implications for understanding how D2HG affects nonneoplastic cells in an IDH1mut glioma.
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