Ethnic distribution and clinical impact of serum tumor marker abnormalities in metastatic breast cancer patients.

e13007 Background: Serum tumor markers (STMs) - CA15-3, CA27-29 and CEA - are commonly used for surveillance and metastatic breast cancer (mBC) treatment monitoring. The ethnic distribution and prognostic impact of each STM are poorly understood. Methods: This research was a multi-center retrospective study including records of patients with confirmed mBC and ≥2 values for each STM. Median and maximum (max) values of STMs for each patient were analyzed. Mann-Whitney (M-W) and Kruskal-Wallis tests, as well as Spearman correlations, comprised statistical analyses; significant findings were declared at p < 0.05. Results: The study included 237 patients: 9.3% Hispanic (H), 91.6% > 50 years old, 57.2% and 37.6% with history of alcohol and tobacco use, respectively. All STMs were consistently lower in H compared to non-H (Table 1) and were not associated with alcohol/tobacco use, specific mBC histology/subtype or TP53 mutation. Higher median CA15-3 and CA27-29, but not median CEA, statistically correlated with longer time from diagnosis to new metastatic deposit (p = 0.003 and 0.016, respectively). All median and max STM values directly correlated with an increasing number of metastatic sites (p≤0.003) and lines of chemotherapy (p≤0.045). Only CEAmax was negatively correlated with higher number of HER2 therapies (p = 0.042). No STM was correlated with time from diagnosis to mBC-related death in H and non-H patients. Conclusions: STMs remain helpful mBC monitoring tools as the degree of their elevation correlated with increasing number of metastatic sites and lines of chemotherapy, while CA 15-3 and CA27-29 elevation positively correlated with time to first progression. However, STMs lack prognostic information and showed no statistically significant differences by race, alcohol/tobacco use or specific mBC histology/subtype. To our knowledge, this study is the first to suggest ethnic variability in STMs. Reasons for lower STM values in Hispanics will need to be elucidated in larger studies. STM Medians and maximums with interquartile ranges (IQRs) by ethnicity. Ethnicity CA 15-3 median (U/ml) CA 15-3 max (U/ml) CA 27-29 median (U/ml) CA 27-29 max (U/ml) CEA median (ng/ml) CEA max (ng/ml) Non-Hispanic 30.50 (19.00-86.5) 101.00 (32.00-464.00) 55.0 (33.50-134.25) 152.00 (58.00-527.25) 4.30 (1.90-9.45) 9.50 (3.20-47.70) Hispanic 16.00 (11.75-45.50) 35.00 (17.00-94.00) 33.50 (20.12-82.75) 64.50 (26.50-147.50) 2.85 (2.00-4.25) 3.85 (2.65-13.17) P-value (M-W) 0.009* 0.014* 0.022* 0.011* 0.415 0.065