Abstract P6-01-01: A study of clinical outcome and biomarker profiles of Japanese breast cancer patients according to mammographic density
Authors: Takigami Naoko , Tamaki Kentaro , Kamada Yoshihiko , Uehara Kano , Tsuchiya Seiko , Terukina Shigeharu , Ishida Takanori , Miyashita Minoru , McNamara Keely May , Sasano Hironobu , Tamaki Nobumitsu 
Published: March 2020

Abstract
Introduction: Mammographic density (MD) has been reported to be associated with increased risk of breast cancer development. In addition, the association of MD with breast cancer subtypes has been proposed in Caucasian breast cancer patients but this has remained virtually unknown in Asian patients. Therefore, in this study, we retrospectively examined the subtypes and clinical prognosis in Japanese cancer patients according to their MD. Method: We retrospectively examined 781 mammograms of breast cancer patients from March 2013 to March 2016 at Nahanishi Clinic, Okinawa, Japan. In this study, MD was tentatively classified according to the recommendation of the Japanese Central Organization on Quality Assurance of Breast Cancer Screening, based on the proportion of fat area as follows; (a) extremely high dense:10-20%, (b) heterogeneously dense:40-50%, (c) scattered fatty:70-90%, (d) fatty: almost all the breast fat. “Dense breast” includes extremely high and heterogeneous dense. We also evaluated the rates of recurrence and breast cancer specific death according to MD defined as above. The status of breast cancer subtypes was also compared between dense and non-dense breasts, and between pre-menopausal and post-menopausal women. Result: Among 781 cases examined, 365 were classified as dense breasts and 416 as non-dense breasts. The median age of all the patients examined was 57 years old. The age was significantly younger (50.4 vs 63.4 years old P&lt;0.001), and the BMI significantly lower (22.2 vs 25.9 P&lt;0.001) in the dense breast group. No significant differences of the breast cancer mass diameter were detected between dense and non-dense breasts (23mm vs 20.8mm P=0.10). At 49.7 months median observation period, the rate of breast cancer death (HR: 0.98(0.43-2.21), P=0.96) nor the recurrence rate (HR:1.64(0.95-2.84), P=0.078) were not different between dense and non-dense breasts. The rate of hormone receptor positive breast cancer was significantly higher in non-dense breasts (OR 0.66(0.44-0.98) P=0.049) but HER2 positivity was significantly higher in dense breasts (OR 1.66(1.11-2.49) P=0.017). The triple negative subtype was significantly higher in non-dense breasts (OR 0.49(0.27-0.929) P=0.032). Ki67 labeling index was higher in dense breast patients (24.3% vs 20.3%,P=0.004). There were no significant differences in the rate of hormone positive tumors between dense and non-dense breasts in patients under 40 years of age (OR 1.14(0.27-4.79), P=0.85) but its rate was significantly lower in patients over 60 years of age with dense breasts (OR 0.51(0.26-0.98), P=0.043). In addition, in a separate analysis of all women who regularly received mammogram examination at our clinic during the same period, among 2308 subjects under the age of 40, 1892 subjects had dense breasts and 417 subjects had non-dense breasts, in which the incidence of hormone positive breast cancer was not significantly different between these two groups (OR 0.92(0.47-1.79), P=0.94). However, among the 4340 subjects over 60 years of age, the incidence of hormone positive breast cancers in the 1158 dense group was significantly smaller than the 3182 non-dense group (OR 0.73(0.55-0.97), P=0.033). Conclusion: Results of our present study firstly demonstrated that the rate of breast cancer death and recurrence was not significantly different between patients with dense and non-dense breasts. However, our results specifically taken from Asian women indicated that the rate of hormone positive tumors was significantly higher in non-dense breasts, especially in post-menopausal women, contrary to existing reports which suggested that was higher in dense breast in Caucasian women.
Citation Format: Naoko Takigami, Kentaro Tamaki, Yoshihiko Kamada, Kano Uehara, Seiko Tsuchiya, Shigeharu Terukina, Takanori Ishida, Minoru Miyashita, Keely May McNamara, Hironobu Sasano, Nobumitsu Tamaki. A study of clinical outcome and biomarker profiles of Japanese breast cancer patients according to mammographic density [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-01-01.