Abstract P6-01-04: Changes in Ki67 expression in breast cancer during the menstrual cycle and menopause
Authors: Fujita Takashi , Sawaki Masataka , Hattori Masaya , Kondo Naoto , Yoshimura Akiyo , Ichikawa Mari , Adachi Yayoi , Hisada Tomoka , Kotani Haruru , Ishigro Junko , Iwata Hiroji 
Published: May 2015

Abstract
Background
Previous studies have shown that the menstrual cycle phase can influence PgR status of breast cancer. But data on whether the menstrual cycle phase affects Ki67 expression is inconsistent. This study aims to compare the Ki67 expression on ultrasonography guided vacuum-assisted breast biopsy (US-guided VABB) with matched breast cancer surgical specimens.
Materials and Methods
In 120 breast cancer patients without neoadjuvant chemotherapy who underwent US-guided VABB and surgical resection from April 2008 and March 2012 at Aichi Cancer Center Hospital, we examined the concordance of Ki67 level between US-guided VABB and surgical specimen. All the US-guided VABB were performed using 11-gauge Mammotome. In this study, the Ki67 cut-off level for positivity was defined at 20%.
Two phases of the menstrual cycle were pre-defined as indicated; phase 1 (low estrogen) days 27–35 or 1–6; phase 2 (high and intermediate estrogen) days 7–26 (Hayes BP, et al. Breast Cancer Res Treat 2013).
We defined the three groups as follows: the non-matching menstrual phase group (different menstrual cycle phase at the time of biopsy and surgery: n=18), the matching menstrual phase group (same menstrual cycle phase at the time of biopsy and surgery: n=25), and the post-menstrual group (n=77).
We evaluated the discordance of Ki67 expression between US-guided VABB and surgical specimens in the three groups.
Results
A differential expression of Ki67 was found in 13 patients and the concordance rate of Ki67 expression between US-guided VABB and surgical specimens was 89.2% with a Kappa statistic value of 0.78. (The concordance rate of ER, PgR, and HER2 status were 96.4%, 90.2%, and 97.0%, respectively.)
There were no major differences in tumor and patient characteristics (age, pathological tumor size, and number of biopsy specimens) between the non-matching menstrual phase group and the matching menstrual phase group.
The discordance rate of Ki67 expression for the non-matching menstrual phase group, the matching menstrual phase group, and the post-menstrual group were 22.2%, 4.0%, and 10.4%, respectively. In the patients with ER positive tumors, the discordance rate of Ki67 expression for the non-matching menstrual phase group, the matching menstrual phase group, and the post-menstrual group were 23.5%, 4.8%, and 10.9%, respectively. The discordance rate of Ki67 expression tended to be higher in the non-matching menstrual phase group than in the matching menstrual phase group. (p=0.11)
Conclusions
Though limited by the low number of patients, our study suggested that the menstrual cycle could affect Ki67 expression as patients with different menstrual cycle phase at the time of biopsy and surgery show discordant results.
Prospective evaluation of Ki67 expression in premenopausal patients with ER positive tumor is needed.
Citation Format: Takashi Fujita, Masataka Sawaki, Masaya Hattori, Naoto Kondo, Akiyo Yoshimura, Mari Ichikawa, Yayoi Adachi, Tomoka Hisada, Haruru Kotani, Junko Ishigro, Hiroji Iwata. Changes in Ki67 expression in breast cancer during the menstrual cycle and menopause [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 P6-01-04.