Characterizing Response to Neoadjuvant Chemotherapy in Invasive Lobular Breast Carcinoma

Pathological complete response (pCR) after neoadjuvant chemotherapy (NCT) for breast cancer is associated with improved survival and facilitates conservative surgical strategies. Invasive lobular carcinoma (ILC) has been observed to have decreased response to NCT compared with invasive ductal carcinoma (IDC). This study seeks to evaluate national trends in the use of NCT for ILC compared with IDC, and determine if there is a subset of ILC patients who demonstrate favorable response rates.

This is a study using the National Cancer Database. The cohort consisted of patients with stage 1-3 ILC treated between 2010 and 2014, and a reference cohort of patient with IDC. For patients receiving NCT, pCR was assessed and clinically relevant variables were used in multivariable logistic regression models for each histologic subtype, modeling for pCR achievement. Survival analysis was performed for each histologic group to evaluate potential survival benefits of achieving pCR.

Our study cohort consisted of 384,887 women, of which 9.7% had ILC. A significantly lower rate of pCR after NCT was found in the cases of ILC compared with those of IDC (8.7% versus 23.2%). Increased response was seen in ILC patients with HER2-positive and TNBC subtypes. A survival benefit was demonstrated in patients with ILC who achieved pCR.

While response to NCT in patients with ILC is uncommon, our findings demonstrate a selective benefit for patients with HER2-positive tumors and TNBC. In addition, pCR is correlated with a clear survival advantage in ILC.