Response to neoadjuvant chemotherapy in lobular and ductal breast carcinomas: a retrospective study on 860 patients from one institution.

Background: 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).
Patients and Methods: 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.
Results: 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.
Conclusions: 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.