Do breast quadrants explain racial disparities in breast cancer outcomes?

摘要

About one in eight American women will be diagnosed with breast cancer during their lifetime [1]. Incidence of breast cancer is higher among White women (130 per 100,000) compared with Black, Asian American/Pacific Islander (PI) and Hispanic women (126, 93, and 93 per 100,000, respectively) [1]. However, breast cancer mortality rates are higher in Black women [1,2,3] and lower in Asian American/PI and Hispanic American women compared with White women [1]. In addition, breast cancer is one of the leading causes of death among American women, accounting for over 41,000 deaths annually [1]. Tumor location in the breast is an important prognostic factor [4,5,6,7]. The upper-outer quadrant of the breast is the most prevalent site for breast cancer [8], likely due to the larger amount of epithelial tissue in this quadrant compared with other quadrants [9]. Tumors of the outer breast have shown more favorable outcomes than other sites [5, 6, 10, 11]. Specifically, women with tumors of the upper-outer quadrant have better survival compared to those with tumors of other quadrants [12]. Survival rates are diminished in patients with tumors of inner quadrant [6] and tumors of the medial breast [11], likely because these quadrants are more difficult to detect by mammography [13, 14]. Moreover, breast cancer lymphatic metastasis goes not only to the axillary lymph nodes but also to the internal mammary lymph nodes [15], especially for breast cancer located in inner quadrants of the breast. However, the importance of internal mammary lymph node biopsy in the accurate staging and management of breast cancer is controversial [16], thus lack of monitoring and timely treatment of internal mammary lymph nodes may lead to worse outcomes.