Breast cancer in Asian women.

Breast cancer is genetically and clinically heterogeneous. Many studies have attempted to address this complexity, but we are still trying to open the “black box” of this challenging disease. The risk of developing breast cancer, of its recurrence, and of dying of it varies among ethnic populations. We do not fully understand why this ethnic variation exists. The variation is partly explained by differences in personal characteristics and in prognostic indicators. These include variations in, for example, patient age at diagnosis, menstrual and reproductive history, lifestyle factors, family history of breast and other cancer, axillary lymph node status, histologic grade, tumor size, and tumor markers.1 The recent advances of genetic mapping and proteinomics may allow us to better understand how breast cancer develops and progresses. Until then, it remains a daunting task to explain the mechanisms underlying variations in breast cancer among different groups of women. Lin and colleagues studied women diagnosed with breast cancer from 1988 to 1999. We need to be cautious in interpreting their findings because medical practices and treatments may have changed in the past 20 years. A key finding was that Vietnamese women were younger at diagnosis than women from other ethnic groups. This supports the findings of other research showing ethnic variation in age at diagnosis. For example, in a study of women diagnosed with breast cancer in Asian countries, women in both Taiwan and Vietnam were diagnosed at a much younger age than white women in America (Huang A, Cheng S, written communication, 2001). In premenopausal women with breast cancer in Taiwan, the proportion with positive estrogen-receptor status—which is associated with a better prognosis—was greater than in premenopausal white women with breast cancer in America. This difference was not found in postmenopausal women. Unfortunately, Lin and colleagues' study did not look at the premenopausal and postmenopausal age groups separately. They found that Vietnamese women overall were less likely than non-Hispanic whites to have positive estrogen-receptor status. In other words, they were more likely to have cancer with a poor prognosis. A second key finding was that Vietnamese women were significantly more likely to have received mastectomy for their early-stage tumors than women from other ethnic groups. The issue of why Asian women do not receive breast-conserving surgery is an intriguing one. A previous study, of which I was the lead author, indicated that Chinese American women with breast cancer were more likely to have had a radical mastectomy than African American, Hispanic, or white women.2 This could, of course, be explained by factors such as hospital and physician preference, extent of prognostic factors, patient selection, and margin of resection. So, for example, Chinese women may have been treated more radically because they had more aggressive disease. Moreover, their treatment may have reflected the culturally based wishes of the women themselves to be rid of the disease completely. In Lin and colleagues' study, the increased likelihood of having mastectomy among Vietnamese women persisted even after adjusting for tumor characteristics and physician, although adjusting for the hospital of diagnosis did account for some of the ethnic variations in mastectomy use. Further study is needed to elucidate this issue. I asked Scarlett Lin to re-compute the data to separate out Chinese, Japanese, and Filipino women. Chinese and Japanese women were more likely to have had a mastectomy than white women, but the odds ratio was only 1.32 (95% confidence interval, 1.21-1.45) and 1.25 (95% confidence interval, 1.08-1.45), respectively. The odds ratio for Filipino women, on the other hand, was nearly as high as for Vietnamese women—for Filipino women, it was 1.58 (95% confidence interval, 1.42-1.76). Practicing primary care physicians need to be aware that their Asian female patients with breast cancer may be diagnosed at a younger age than women of other ethnic groups, they may have different prognostic indicators, and they may choose different treatments.