Abstract P3-07-26: Characteristics of de novo metastatic breast cancer in California, 2005-2011
Authors: Clarke Christina A , Chu Laura , Tao Li , Wang Lisa , Moy Lisa , Brammer Melissa , Song Chunyan , Green Marjorie , Gomez Scarlett Lin 
Published: May 2015

BACKGROUND: Breast cancer (BC) that is metastatic at initial diagnosis (i.e. de novo metastatic or stage IV) has not been well described, especially in the general population.

OBJECTIVE: To describe demographics, tumor characteristics and survival in a population-based cohort of patients with de novo metastatic BC (MBC).

METHODS: We studied all 6268 de novo MBC cases diagnosed in California women between 1/1/2005 and 12/31/2011, as reported to the California Cancer Registry. Molecular subtypes were classified according to HER2 and hormone receptor (HR, based on estrogen and progesterone receptor) status. Median overall survival (OS) was calculated by Kaplan-Meier methods. Cox proportional hazards regression was used to assess independent predictors of OS.

RESULTS: 5% of all newly diagnosed BC were metastatic, representing 6% of all newly diagnosed HR+/HER2+, 8% of all HR-/HER2+, 4% of all HR+/HER2- and 6% of all triple negative BC (TNBC). Compared to patients with early BC, MBC patients were of similar age (mean age at diagnosis, (interquartile range): 61,(51-71) vs. 60, (50-70) years)). They were slightly more likely to be black (10% vs. 6%) or Hispanic (19% vs. 17%) but substantially more likely to be unmarried (56% vs. 40%), to live in neighborhoods of the lowest socioeconomic quintiles (39% vs. 29%), and to have public (e.g., Medicaid) or no insurance (39% vs. 21%). Most MBC patients presented with large tumors; however, 13% of patients had tumor sizes 2 cm or less, compared with 60% of patients with early BC (of TNBC: 15% MBC vs. 44% early BC were ≤2 cm). A minority of patients with de novo MBC received breast surgery (39%), with 24% receiving full or partial mastectomy, 9% lumpectomy, 3% bilateral mastectomy and 3% other/unknown surgery . 64% of de novo MBC patients received chemotherapy and 33% received radiation.

Median survival after MBC diagnosis was 27 months (mos), but varied substantially by patient characteristics including age (&lt;40: 40 mos, 85+: 8 mos), race/ethnicity (Asian: 34 mos, black: 16 mos), and neighborhood socioeconomic quintile (lowest: 20 mos, highest 34 mos) and molecular subtype (HR+/HER2+: 45 mos, TNBC: 12 mos). In a multivariate Cox model including all available variables, TNBC was the most important predictor of death (Hazard Ratio 2.8, 95% CI: 2.4-3.3 vs. HR+/HER2+). Other significant and important predictors included HR-/HER2+ subtype (Hazard Ratio 1.6, 95% CI: 1.3-18 vs. HR+/HER2+), being unmarried, living in low socioeconomic status neighborhoods, and high tumor grade status.

CONCLUSIONS: In this large diverse population, de novo MBC was more likely to be diagnosed for certain breast cancer subtypes, and among minority and underserved women (black or Hispanic race, low socioeconomic neighborhood, no or public health insurance) that may have contributed to the detection of their tumor only after it had metastasized. A high proportion of patients with MBC are not treated surgically, but most receive chemotherapy. Median survival remains poor, with worse survival strongly associated with tumor biology (triple negative and HR-/HER2+ molecular subtypes) and patient characteristics indicative of low socioeconomic status.

Citation Format: Christina A Clarke, Laura Chu, Li Tao, Lisa Wang, Lisa Moy, Melissa Brammer, Chunyan Song, Marjorie Green, Scarlett Lin Gomez. Characteristics of de novo metastatic breast cancer in California, 2005-2011 [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 P3-07-26.