L. Qu1, C. Perez1, C. Godellas1, F. Vaince1 1Loyola University Chicago Stritch School Of Medicine,Surgery,Maywood, IL, USA
Introduction:
Neoadjuvant treatment (NAT) for locally advanced breast cancer can downstage disease prior to surgery, thereby allowing patients to become candidates for breast conservation therapy. Tumor histology has been suspected to impact treatment response to NAT, though current data is limited. We compared response to NAT in patients with invasive ductal carcinoma (IDCA) and invasive lobular carcinoma (ILCA).
Methods:
An IRB-approved retrospective chart review was conducted on breast cancer patients treated with NAT followed by surgery at an academic tertiary care center between September 2013 and July 2018. Two cohorts (IDCA and ILCA) were identified and compared with specific attention to tumor biology, nodal status, and operation performed. Fisher’s Exact Test was used for statistical analyses.
Results:
A total of 231 patients were identified, of which 206 (89%) had IDCA and 25 (11%) had ILCA. Of IDCA patients who underwent NAT followed by surgery, 34% achieved pathologic complete response (pCR) compared to 12% of ILCA patients (p=0.02). There were no significant differences between the IDCA and ILCA cohorts in terms of axillary downstaging or rate of breast conservation surgery. Lobular tumors were larger at presentation (4.1 cm compared to 3.8 cm for ductal tumors) and showed smaller mean decrease in tumor size following NAT (35% compared to 62% for ductal tumors). Fifty percent of patients with IDCA had triple negative (TN) or human epidermal growth factor receptor 2 (Her2+) disease; of these, 48% achieved pCR. Conversely, only 12% of patients with ILCA had TN or Her2+ disease. The majority (88%) of ILCA patients were hormone receptor (HR)+/Her2-. Amongst the HR+/Her2- subgroup, there were no significant differences between the IDCA and ILCA cohorts in terms of pCR, axillary downstaging, or rate of breast conservation surgery. However, the mean decrease in tumor size following NAT was more comparable in this subgroup at 49% and 41% for IDCA and ILCA tumors, respectively.
Conclusion:
Patients with IDCA are more likely to achieve pCR to neoadjuvant therapy than patients with ILCA, though there are no significant differences between groups in terms of axillary downstaging to node-negative disease and rate of breast conservation surgery following NAT. A clinical and pathologic response to NAT can still be anticipated in ILCA tumors, particularly considering the influence of tumor biology. Consequently, a neoadjuvant approach to ILCA should not be dismissed on histology alone.