Response to neoadjuvant chemotherapy in ductal compared to lobular carcinoma of the breast: a meta-analysis of published trials including 1,764 lobular breast cancer

Infiltrating lobular carcinoma (ILC) of the breast is associated with greater oestrogen receptor expression and poorer response to neoadjuvant chemotherapy, when compared to infiltrating ductal carcinoma (IDC). In order to compare the pathological complete response rate (pCR) and breast conserving surgery (BCS) in patients with ILC versus IDC treated with neoadjuvant chemotherapy, we performed a systematic review and meta-analysis of all published studies. A search of PubMed, EMBASE, the Web of Science, SCOPUS and the Cochrane Central Register of Controlled Trials was performed to identify studies that investigated pCR, clinical response and BCS in patients with ILC that were treated with neoadjuvant chemotherapy. Random-effect models were adopted to estimate the summary odds ratio (OR), and the publication bias was evaluated using a funnel plot and Egger's regression asymmetry test. Seventeen studies were included (one randomized controlled trial, three prospective series and 13 retrospective trials), for a total of 12,645 IDCs and 1,764 ILCs to be compared. Ductal carcinoma of the breast was associated with a better pCR (from 5.9 to 16.7 %; OR = 3.1, 95 % CI 2.48-3.87, P < 0.00001) and rate of BCS (from 35.4 to 54.8 %; OR = 2.1, 95 % CI 1.8-2.45, P < 0.00001) compared to ILC. The overall pCR rates and BCS decreased in the ILCs compared with IDC when treated with neoadjuvant chemotherapy.