• be younger at diagnosis
• African American
• overweight and/or obese at diagnosis if premenopausal
The were less likely to breastfeed for long periods—more than four months—and were more likely to not breastfeed if they had at least three children.
The study consisted of 2280 women diagnosed with invasive breast cancer (stages I, II, or IIIA) between 1997 and 2000 and recruited primarily from the Kaiser Permanente Northern California Cancer Registry and the Utah Cancer Registry. They were between 18 and 70 years old and between 11 and 39 months post-diagnosis, free of recurrence, and with no history of other cancers in the five years prior to enrollment.
Tumor subtypes the used and the percentage in that group:
Luminal A: ER positive and/or PR positive, and Her2 negative (73.4%)
Luminal B: ER positive and/or PR positive, and Her2 positive (11.6%)
Triple negative: ER negative, PR negative, and Her2 negative (11.3%)
Her2-overexpressing: ER negative, PR negative, and Her2 positive (3.7%)
Luminal B cases were more likely to be younger at diagnosis and were less likely to consume alcohol or use hormone replacement therapy.
Her2-overexpressing cases were more likely to be younger at diagnosis, less likely to use hormone replacement therapy, and Hispanic or Asian.
Some other interesting stats:
•The majority of the whites (75.3%), Asians (71.4%), Hispanics (68.5%), other (68.5%), and African Americans (59.4%) had luminal A tumors.
• Her2-overexpressing tumors were least common among all races/ethnicities (whites 3.1%, African Americans 3.2%, Asians 6.4%, Hispanics 6.6%, other 5.5%).
• African Americans had the highest prevalence of the triple negative subtype (28.4%) compared with the other races/ethnicities (whites 10.5%, Asians 6.3%, Hispanics 10.7%, other 13.0%).
•African Americans (average age: 56.2) and Asians (average:54.8 years) were more likely to be diagnosed at a younger age.
•Whites were more likely to be diagnosed at an older age (59.8).
•, Asians (59.1%) were less likely to be post-menopausal than whites.
(75.6%), African Americans (71.4%), and other races/ethnicities (72.9%).
• A family history of breast cancer was more common among whites (22.6%) and other
races/ethnicities (24.1%), than among the other groups.
• African Americans and Hispanics had more biological children and were younger during their first pregnancy.
• Whites were more likely to have consumed alcohol while Asians were more likely to have never smoked.
• More whites had used HRT (76.2%).
• Fewer Asians (44.1%) had used oral contraceptives.
• African Americans were more obese at diagnosis.
The study was published in the May 2009 Breast Cancer Research, an open access journal. Download a PDF here. Or read the abstract.
SOURCE: Kwan, ML, Kushi, L, Weltzien,E, Maring, B, Kutner, S, Fulton, R, Lee, M,Ambrosone, C, Caan,B, “Epidemiology of breast cancer subtypes in two prospective cohort studies of
breast cancer survivors,” Breast Cancer Research, 2009, 11:R31.