Abstract P3-05-14: Clinicopathological features of early breast cancer in Japanese premenopausal women
Authors: Tajiri Wakako , Koh Sumire , Nakamura Yoshiaki , Kawasaki Junji , Koi Yumiko , Koga Chinami , Ijichi Hideki , Tokunaga Eriko 
Published: March 2023

Background: Breast cancer incidence is constantly increasing in Japan. The age-specific incidence rates (ASIRs) of breast cancer shows two peaks, at ages 45-49 and 60-64, in Japan. Therefore, the incidence rate of breast cancer in Japanese premenopausal women is higher compared to the Western countries. In our study, we clarified the clinicopathological characteristics of Japanese premenopausal breast cancer.

Patients and Methods: The total of 1,220 premenopausal breast cancer patients treated for early breast cancer, at stage 0-IIII, between 2010 and 2021. The patients were divided into three age groups; aged under 40 (group A, n=258, 21.1%), aged 40 to 45 (group B, n=428, 35.1 %), and aged 46 and over (group C, n=533, 43.7%). Information regarding the clinicopathological characteristics was collected from the medical records.

Result: Significantly longer periods form from menarche to the breast cancer onset (p&lt; 0.0001), larger number of history of pregnancy (p&lt; 0.0001), and higher BMI (25 or higher) (p=0.0091), and more habitual drinking histories (p=0.0029) were recognized in group C. In premenopausal onset, ER-positive status is higher (p=0.0022), the histological grade is lower (p=0.0094), as age increases, and more negative PgR status(p=0.0019), and more triple negative breast cancer (p=0.0002) were shown in group A. Hormone receptor-positive HER2-negative breast cancers under 45 years of age (group A, B) were more likely to receive neoadjuvant chemotherapy than those aged 46 years and older (group C) (p=0.0077), but there was no age-related difference for other subtypes. The association between clinicopathological factors and distant relapse-free survival (DRFS) in each age group was analyzed. is associated with higher grades (group A, p=0.0638、group B, p=0.0208, group C, p=0.0006) , negative PgR status (group A, p=0.0379,group B, p=0.0683,group C, p=0.0042), and lower ER expression (group B, p=0.0395 group C, p=0.0021) were significantly associated with poor DRFS. Similarly, in overall survival, higher grades (group A, p=0.0257,group B, p=0.0027,group C, p=0.0111) ,negative PgR status (group A, p=0.0162,group B, p&lt; 0.0001,group C, p=0.0003), and lower ER expression (group C, p=0.0003) were significantly poor prognosis. In univariate analyses, higher grade, negative PgR status, and ER negative/low-positives were risk factors, and in multivariate analyses, higher grade was a risk factor for poor prognosis

Conclusion: We found that there are many clinicopathological characteristics related to poor prognosis in premenopausal breast cancer patients aged under 40, such as low or negative ER expression, higher histological grade, and negative PgR status.

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Citation Format: Wakako Tajiri, Sumire Koh, Yoshiaki Nakamura, Junji Kawasaki, Yumiko Koi, Chinami Koga, Hideki Ijichi, Eriko Tokunaga. Clinicopathological features of early breast cancer in Japanese premenopausal women [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-14.