Breast Cancer Incidence and Behavior in Younger Patients: A Study From the Surveillance, Epidemiology and End Results Database

Abstract

Background: Breast cancer screening for women less than 40 years old is practically non-existent. Since screening can detect cancer at an early stage, not having a surveillance guideline for breast cancer in younger women can result in detection of the cancer at advanced stages. The purpose of this study was to investigate the incidence and behavior of breast cancer in younger women. Methods: The Surveillance, Epidemiology and End Results (SEER) registry data from 2004 to 2014 were accessed for the study. All women diagnosed with breast cancer and with complete information were included in the study. The data were further divided into two groups based on the age of the patient at the time of diagnosis. The younger group consisted of women < 40 years old (group 1) and the older group consisted of women ≥ 40 years old (group 2). Both groups were compared on demography and characteristics of the cancer. The continuous variables were tested using Student's t-tests and categorical variables were compared using Chi-squared or Fisher's exact tests. Multivariate analysis was done to find the association of high-grade cancer using a logistic regression model. All P-values are two-sided and values < 0.05 were considered statistically significant. Results: Of 599,782 patients who satisfied the inclusion criteria, 28,243 (4.71%) diagnosed with breast cancer were younger women aged < 40 years old. A higher proportion of these younger women presented with larger tumor sizes (between 5.1 and 10.0 cm) (11.61% vs. 5.70%, P < 0.001), poorly differentiated cancer cells (55.88% vs. 32.85%, P < 0.001) and triple negative receptors (6.83% vs. 3.81%, P < 0.001) than older women respectively. Younger age was significantly associated with high-grade tumor at presentation when controlling for race and marital status. There was roughly 3% increased risk of a high-grade tumor with each decrease of 1 year (odds ratio 0.97, 95% confidence interval 0.96-0.99, P = 0.001). Conclusion: This study found that the proportion of breast cancer cases in younger women was just below 5%; however, when the cancer was diagnosed, these women presented in advanced stages and more aggressive cancer types.

Breast cancer in young women: Imaging and clinical course

“…Because patients younger than 40 do not routinely undergo mammographic screening, it is not surprising that the vast majority of patients in our study presented for evaluation of a palpable mass, or that their cancers presented at a larger size than is typically seen in the conventional screening population 5 …”

“…There is currently no widely prescribed breast cancer screening program for AYA women without known risk factors for the disease 2–4 . Disease in young patients may have worse prognosis, 5,6 present at a later stage than cancer in older women, and may reflect unique age‐related biology 7 . There are unique considerations during treatment of this population, including long‐term mitigation of recurrence risk 8 and preservation of fertility 9 …”

Cellular Plasticity and Heterotypic Interactions during Breast Morphogenesis and Cancer Initiation

“…First, are the tumors expressing hormone receptors (HR), where a subset of cells (as low as 1%) within the tumor express either estrogen receptor alpha (ERα) or progesterone receptor (PR), or both. These tumors, which generally affect postmenopausal women in greater frequencies [ 39 , 40 ], are more numerous (up to 70%) than tumors with amplification of human epidermal growth factor-2 (HER2) or triple negative (TN) tumors, lacking both HR and HER2 expression [ 41 ]. The HR+ tumors in general have a lower grade than HER2 or TN tumors, with the cells in the tumor resembling normal breast cells to a greater extent, even though the tumor histoarchitecture is vastly different.…”

“…Lum = luminal, TN/BL = triple-negative/basal-like, HR = hormone receptor. Statistics adapted from [ 39 , 41 ], based on identifiable tumors.…”

Bimodal Age Distribution in Cancer Incidence

“…This includes derivation of tumors from stem cells committed to luminal differentiation with ER expression versus the development of tumors from stem cells committed to basal differentiation lacking ER expression [34,60]. Several hormonal factors impact an individual's risk of developing breast cancer, including the age of first menarche, age of menopause as well as age of first pregnancy [61]. While the rates of breast cancer are lower in younger women, the tumors characteristics were found to be more likely to be aggressive with higher incidence of distant metastases compared to the older patients [61].…”