Luminal B breast cancer and prognostic value of HER2 overexpression: Retrospective analysis of a single-institution series.

Abstract

e11120 Background: Luminal B is a heterogeneous estrogen-receptor positive breast cancer subtype, with a higher proliferation rate and a poorer prognosis than luminal A. Overexpression of HER2 oncogene identifies tumors with a different clinical behavior. This study evaluates the prognostic role of HER2 expression in luminal B tumors. Methods: We retrospectively analyzed the clinicopathologic characteristics of 2005 early breast cancer pts (I-IIIB clinical stages) diagnosed between 1997 and 2007 at our institution. 47% of pts fulfill luminal B-subtype criteria: ki67≥14%, PR<10% stained cells or HER2(+) in addition to ER≥10% stained cells. HER2 was defined as positive if Herceptest 3+or gene amplification confirmed by FISH. Results: Among 772 luminal B patients who received curative surgery for invasive breast cancer from January 1997 to June 2007, 670 patients were included in this analysis, and 212 (27,4%) cases were HER2(+). Median age was 54.4 years (range: 27-87 years). Histologic subtype was as follows: ductal 562 pts (83.9 %); lobular 82 pts (12.2%) Histologic grade: I: 15.1 %, II: 44.8 % , and III: 39 %. Tumor characteristics according to HER2 status were similar, as described in table. With a median follow-up of 82 months, overall relapse rate was 23%. Median DFS or OS were not reached. At the current analysis, no differences were observed in DFS (p 0.64) or OS (p 0.53) in Kaplan-Meier estimates between HER2 positive and negative groups. Conclusions: Luminal B subtype include populations with different behaviour and prognosis. In our series patients with HER2 (+) tumors have a similar prognosis as HER2(-) subgroup for luminal B classified patients. Tumor or patient characteristic HER2-negative subgroup (% pts) HER2-positive subgroup (% pts) Median age 54.7 y 53.4 y Median Ki67 value 20 20 Tumor size T1 T2 T3 T4 46.2 40.3 8.6 4.2 44.9 44.9 4.8 7.2 Node status N0 N1 N2 N3 52.0 28.8 11.8 7.2 57.5 21.7 14.6 6.13 Histologic type Ductal Lobular 80 15 92 5.6 Adjuvant chemotherapy None No taxanes nor anthracyclines Anthracyclines without taxanes Anthracyclines and taxanes 19.7 15.1 24.3 23.9 16.5 20.7 29.7 13.6 Adjuvant trastuzumab None 15