HER2-positive invasive lobular carcinoma: a rare breast cancer which may not necessarily require anti-HER2 therapy. A population-based study.

BACKGROUND: HER2-positive (HER2 +) invasive lobular breast cancer (ILC) is rare and poorly characterised. In particular, patient outcomes compared to those associated with HER2 + invasive ductal cancer (IDC) and HER2-negative (HER2 -) ILC, as well as the benefits of anti-HER2 therapy, are not well established. METHODS: We analysed the data from the Côte d'Or Registry of Breast and Gynaecological Cancers (France) for all patients diagnosed with early-stage HER2 + ILC (62 cases), HER2 + IDC (833 cases) and HER2 - ILC (685 cases) between 1998 and 2015 to compare overall and disease-free survival (OS and DFS) between these groups in correlation with anti-HER2 therapy. RESULTS: ILCs were associated with older age, larger tumours, lower histological grades, higher hormonal receptor positivity rates and multifocality, and more common endocrine therapy. OS and DFS between the three groups did not differ. We found that anti-HER2 therapy was associated with a survival benefit in patients with HER2 + IDC. In contrast, the survival of HER2 + ILC patients was not improved by anti-HER2 treatment, remaining close to that of HER2 - ILC patients. CONCLUSION: HER2 + ILC seems not to be associated with better outcomes than HER2 + IDC but may not differ from HER2 - ILC in terms of survival.

Prognosis of local invasive relapses after carcinoma in situ of the breast: a retrospective study from a population-based registry.

PURPOSE: The prognosis of local invasive recurrence (LIR) after prior carcinoma in situ (CIS) of the breast has not been widely studied and existing data are conflicting, especially considering the specific prognosis of this entity, compared to de novo invasive breast cancer (de novo IBC) and with LIR after primary IBC. METHODS: We designed a retrospective study using data from the specialized Côte d'Or Breast and Gynecological cancer registry, between 1998 and 2015, to compare outcomes between 3 matched groups of patients with localized IBC: patients with LIR following CIS (CIS-LIR), patients with de novo IBC (de novo IBC), and patients with LIR following a first IBC (IBC-LIR). Distant relapse-free (D-RFS), overall survival (OS), clinical, and treatment features between the 3 groups were studied. RESULTS: Among 8186 women initially diagnosed with IBC during our study period, we retrieved and matched 49 CIS-LIR to 49 IBC, and 46 IBC-LIR patients. At diagnosis, IBC/LIR in the 3 groups were mainly stage I, grade II, estrogen receptor-positive, and HER2 negative. Metastatic diseases at diagnosis were higher in CIS-LIR group. A majority of patients received adjuvant systemic treatment, with no statistically significant differences between the 3 groups. There was no significant difference between the 3 groups in terms of OS or D-RFS. CONCLUSION: LIR after CIS does not appear to impact per se on survival of IBC.