Infiltrating lobular carcinoma of the breast: tumor characteristics and clinical outcome

Abstract

Introduction: Invasive lobular carcinoma (ILC) comprises approximately 10% of breast cancers and appears to have a distinct biology. Because it is less common than infiltrating ductal carcinoma (IDC), few data have been reported that address the biologic features of ILC in the context of their clinical outcome. In the present study we undertook an extensive comparison of ILC and IDC using a large database to provide a more complete and reliable assessment of their biologic phenotypes and clinical behaviors.

Methods: The clinical and biological features of 4140 patients with ILC were compared with those of 45,169 patients with IDC (not otherwise specified). The median follow-up period was 87 months.

Results: In comparison with IDC, ILC was significantly more likely to occur in older patients, to be larger in size, to be estrogen and progesterone receptor positive, to have lower S-phase fraction, to be diploid, and to be HER-2, p53, and epidermal growth factor receptor negative. It was more common for ILC than for IDC to metastasize to the gastrointestinal tract and ovary. The incidence of contralateral breast cancer was higher for ILC patients than for IDC patients (20.9% versus 11.2%; P < 0.0001). Breast preservation was modestly less frequent in ILC patients than in IDC patients. The 5-year disease-free survival was 85.7% for ILC and 83.5% for IDC (P = 0.13). The 5-year overall survival was 85.6% for ILC and 84.1% for IDC (P = 0.64).

Conclusion: Despite the fact that the biologic phenotype of ILC is quite favorable, these patients do not have better clinical outcomes than do patients with IDC. At present, management decisions should be based on individual patient and tumor biologic characteristics, and not on lobular histology.

Figure 1

(a) The 5-year disease-free survival (DFS) was 85.7% (95% confidence interval [CI] 84.4–87.1%) for invasive lobular carcinoma (ILC) versus 83.5% (95% CI 83.1–84.0%) for invasive ductal carcinoma (IDC; P = 0.13). (b) The 5-year overall survival (OS) was 85.6% (95% CI 84.2–87.0%) for ILC and 84.1% (95% CI 83.7–84.6%) for IDC (P = 0.64).

Figure 2

The 5-year overall survival (OS) after the first recurrence was 32.8% (95% confidence interval [CI] 28.0–37.6%) for invasive lobular carcinoma (ILC) and 26.7% (95% CI 25.3–28.0) for invasive ductal carcinoma (IDC). The median survival after first recurrence was 22 months (range 0–115 months) for ILC versus 19 months (range 0–119 months) for IDC (P = 0.002).