Abstract P3-06-40: Prognostic impact of PgR and Ki-67 expression in ER-positive and HER2-negative breast cancer patients
Authors: Nishiyama Yasuyuki , Nishimura Reiki , Osako Tomofumi , Okumura Yasuhiro , Arima Nobuyuki 
Published: May 2015

Background:

The 13th St Gallen International Breast Cancer Conference (2013) proposed that conventional and new clinico-pathological factors provided a surrogate subtype classification. Moderate or strong expression of PgR has been proposed as an additional restriction in the surrogate definition of Luminal disease. Ki-67 level is also important for this distinction. We divided ER-positive and HER2-negative breast cancer into 4 groups according to the PgR and Ki-67 expressions. The aim of this study was to evaluate the clinical and prognostic significance of these markers among 4 groups.

Patients and Methods:

We analyzed recurrence-free survival (RFS) in 2100 invasive cancer patients who underwent surgery at our institution between September 2001 and December 2013 retrospectively. Patients with T4, neoadjuvant chemotherapy and adjuvant trastuzumab therapy were excluded. The age of the patients ranged from 25 to 75 years. The subtypes were defined as LA (PgR≥20% and Ki-67&lt;20%; n=677), LB-1 (PgR≥20% and Ki-67≥20%; n=524), LB-2 (PgR&lt;20% and Ki-67≥20%; n=198), LB-3 (PgR&lt;20% and Ki-67&lt;20%; n=187), LH (HER2 positive; n=198), HER2 (non-luminal; n=105), and triple negative (TN, ER- and PgR- and HER2-; n=211). RFS was compared among subtypes using Kaplan-Meier method and logrank test. The median follow-up period was 62.9 months.

Results:

In terms of RFS, patients with LA had significantly better prognosis than other subtypes (p&lt;0.001). Patients with LB-2 had a significantly poorer prognosis than LA, LB-1, LB-3 and HER2 (non-luminal), and the PFS of LB-2 was equivalent to LH (HER2 positive) and TN. Among ER-positive and HER2-negative patients (LA, LB-1, LB-2 and LB-3), LB-2 patients had significantly worse prognosis than the other subtypes in node negative cases (p&lt;0.001). On the other hand, in node positive cases, there was no difference in PFS between LB-2 and LB-3 (p=0.298). Moreover, LB-2 patients showed a significantly worse PFS in the endocrine therapy group (p&lt;0.001). In the chemo-endocrine therapy group, LB-2 and LB-3 had a significantly poorer prognosis than LA; however, there was no difference between LB-2 and LB-3 (p=0.371).

Conclusion:

In luminal type breast cancer, patients with LB-2 (PgR&lt;20% and Ki-67≥20%) had the worst prognosis. On the other hand, in the chemo-endocrine therapy group, LB-2 and LB-3 (PgR&lt;20% and Ki-67&lt;20%) had similar and poorer prognosis. These findings suggested that lower expression of PgR (&lt;20%) correlated with lower PFS and lower sensitivity to endocrine therapy, and lower Ki-67 index (&lt;20%) reflected lower sensitivity to chemotherapy. The expression of PgR and Ki-67 might provide a clinical significance in the luminal type.

Citation Format: Yasuyuki Nishiyama, Reiki Nishimura, Tomofumi Osako, Yasuhiro Okumura, Nobuyuki Arima. Prognostic impact of PgR and Ki-67 expression in ER-positive and HER2-negative breast cancer patients [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-06-40.