Intrathecal trastuzumab for leptomeningeal carcinomatosis in patients with human epidermal growth factor receptor 2 positive breast cancer

There has been recent increase in incidence of leptomeningeal carcinomatosis, possibly due to widespread use of adjuvant trastuzumab and its known poor CNS penetration. Currently there are limited therapeutic options for these patients and outcome is poor. We report two cases of women with HER2 positive breast cancer who developed leptomeningeal carcinomatosis for which they were treated with intrathecal trastuzumab in combination with systemic therapy. Both patients had rapid symptomatic benefit and radiological response and remained progression free for at least seven months. Intrathecal trastuzumab can be considered a reasonable therapeutic option for these difficult to treat patients.