Tumor markers are becoming increasingly important in breast cancer research because of their impact on prognosis, treatment, and survival, and because of their relation to breast cancer subtypes. The triple‐negative phenotype is important because of its relation to the basal‐like subtype of breast cancer.

Using the population‐based California Cancer Registry data, we identified women diagnosed with triple‐negative breast cancer between 1999 and 2003. We examined differences between triple‐negative breast cancers compared with other breast cancers in relation to age, race/ethnicity, socioeconomic status (SES), stage at diagnosis, tumor grade, and relative survival.

A total of 6370 women were identified as having triple‐negative breast cancer and were compared with the 44,704 women with other breast cancers. Women with triple‐negative breast cancers were significantly more likely to be under age 40 (odds ratio [OR], 1.53), and non‐Hispanic black (OR, 1.77) or Hispanic (OR, 1.23). Regardless of stage at diagnosis, women with triple‐negative breast cancers had poorer survival than those with other breast cancers, and non‐Hispanic black women with late‐stage triple‐negative cancer had the poorest survival, with a 5‐year relative survival of only 14%.

Triple‐negative breast cancers affect younger, non‐Hispanic black and Hispanic women in areas of low SES. The tumors were diagnosed at later stage and were more aggressive, and these women had poorer survival regardless of stage. In addition, non‐Hispanic black women with late‐stage triple‐negative breast cancer had the poorest survival of any comparable group. Cancer 2007. © 2007 American Cancer Society.