We compared the impact of neoadjuvant chemotherapy on pathologic response and outcome in operable invasive lobular breast carcinoma (ILC) and invasive ductal breast carcinoma (IDC).

We extracted from our database all patients with pure invasive lobular (n=118, 14%) or pure invasive ductal carcinomas (n=742, 86%). Their treatment included neoadjuvant chemotherapy, adapted surgery, radiotherapy and adjuvant hormonal treatment.

Compared with IDC, ILC presented with larger tumors (T3: 38.1% versus 21.4%, P=0.0007), more N0 nodes status (55.9% versus 43.3%, P=0.01), less inflammatory tumors (5.9% versus 11.8%, P=0.01), more hormone receptor positivity (65.5% versus 38.8%), lower histological grade (P<0.0001). Final surgery was a mastectomy in 70% of patients with ILC (34% were reoperated after initial partial mastectomy) and in 52% of IDC after 8% of reoperation (P=0.006). A pathological complete response (pCR) was achieved in 1% of ILC and 9% of IDC (P=0.002). The outcome at 60 months was significantly better for ILC, but histologic type was not an independent factor for survival in multivariate analysis.

ILC appeared less responsive to chemotherapy but presented a better outcome than IDC. While new information on biological features of ILC is needed, we consider that neoadjuvant endocrine therapy in hormone receptor-positive ILC may be a more adapted approach than neoadjuvant chemotherapy.