Is Trastuzumab Effective for Lobular Breast Cancers?

Invasive lobular carcinoma (ILC), which accounts for up to 15% of all breast cancers, has been associated with distinct clinical-pathologic features, including relative chemo-insensitivity, bilateral breast involvement, and metastases to serous surfaces. Most classic ILCs are estrogen receptor(ER)-positive and infrequently human epidermal growth factor receptor 2 (HER2)-positive, although some variants of ILC (e.g., pleomorphic ILC) have a much higher frequency of HER2-positivity. What has not been clearly defined is whether ILC or its variants benefit less from anti-HER2 therapy than does the more common infiltrating ductal carcinoma (IDC).

To shed light on this issue, investigators reviewed patients enrolled in the recently reported Hercep…