Invasive lobular breast cancer in young patients without adjuvantsystemic treatment: 15-year survival outcomes

Abstract
Purpose Invasive lobular carcinoma (ILC) of the breast typically affects older women. As a result, there is limited research on prognosis and prognostic factors in young women with ILC. Here we set out to determine the long-term outcome and prognostic factors of women under 40 years of age with lymph node-negative (N0), hormone-receptor positive (HR+)/ human epidermal growth-factor receptor 2 negative (HER2-) ILC who did not receive adjuvant systemic treatment (chemoand/or endocrine therapy).
Methods Through the Netherlands Cancer Registry we selected all systemically untreated patients younger than 40years with HR+/HER2-, N0, early breast cancer diagnosed in the Netherlands from 1989-2000. At the time, node-negativity was considered a favorable prognostic marker and guidelines recommended no adjuvant systemic therapy for this subgroup. Distant recurrence-free survival (DRFS), recurrence-free survival (RFS) and overall survival (OS) were assessed according to the STEEP criteria. Uni- and multivariable Cox proportional hazard models were used to assess prognosis, calculating hazard ratios (HR) with confidence interval (CI).
Results Of the n=1138 selected patients, n=95 were histologically classified as ILC and n=805 as invasive breast cancer of no special type (BC-NST), n=238 were classified as other breast cancer subtype. In ILC, tumor grade was not associated with DRFS/RFS or OS (HR for DRFS 1.40, 95%CI 0.42–4.63). However, the presence of lymphovascular invasion (LVI) (adjusted HR DRFS 2.81, 95%CI 1.14–6.94, p<0.05) and multifocality (adjusted HR DRFS 3.28, 95%CI 1.49–7.22, p<0.01) were. When comparing DRFS, RFS and OS in matched low-risk luminal A-like ILC vs. BC-NST, we observed a trend for worse 15-year survival in ILC (15-year DRFS 63% in ILC vs. 74% in BC-NST; HR 1.50, 95%CI 0.98–2.29, p=0.06).
Conclusion In these young patients with systemically untreated N0 ILC we show that grade was not prognostic at 15years follow-up, whereas LVI and multifocality were. Furthermore, ILC had a numerically worse 15-year survival than matched luminal A-like BC-NST.