The overall incidence of breast cancer is generally higher among white women than black women; however, the incidence of a second breast cancer in the opposite breast is higher among black women, according to a study presented at the Fourth AACR Conference on The Science of Cancer Health Disparities, held here Sept. 18-21, 2011.
When cancer is diagnosed in women younger than 45 years old, the incidence of primary breast cancer is higher among blacks than among whites and the cancer tends to be more aggressive.
"When the disease does occur in blacks early on, it tends to be more aggressive, more likely to be estrogen-receptor negative and it is more likely to cause death," said lead researcher Nsouli-Maktabi Hala, a Ph.D. graduate of The George Washington University.
The researchers also found that when cancer is diagnosed at an older age, the incidence is higher among white women. Since most breast cancers are diagnosed in older women, the overall incidence is higher in whites, explained Maktabi.
"While the incidence of breast cancer is generally higher among whites for first-time diagnosis, we found the incidence of the second contralateral diagnosis was higher among blacks," said Maktabi. "This was unexpected blacks usually have a higher mortality rate than whites from the first cancer, so you would expect blacks to have lower rates of second cancers."
"Usually, about 4 percent of all breast cancer patients will present with a second primary cancer contralaterally," Maktabi added.
The researchers used the Surveillance Epidemiology and End Results Registry 9 data to evaluate breast cancer incidence among 415,664 white women and 39,887 black women diagnosed with primary breast cancer at age 19 or older and possible development of a second cancer in the opposite breast.
Results showed that 22,290 (40.7 percent) developed a second primary breast cancer, of which 18,142 (4 percent) occurred in the opposite breast. Incidence of second primary cancers of the opposite breast was higher among black women, and 15,101 (83.2 percent) of second contralateral cancers developed in those who were diagnosed with first breast cancer at age 45 or older.
In addition, contralateral breast cancer tended to occur within the first two years of the primary breast cancer diagnosis.
"This should alert the physician to watch patients very carefully," Maktabi said. "A cancer in one breast should lead to a careful of examination of the other breast over a long period, just in case a cancer develops."
Additionally, average age of the second primary contralateral cancer diagnosis tended to be lower in blacks (59 years of age) than in whites (67 years of age).