Lixin Meng

A case-control study of mammographic densities in Hawaii

Epidemiologic evidence suggests that mammographic densities are markers of breast cancer risk. This project investigated the relation between breast cancer and densities in women of Chinese, Japanese, Filipino, Native Hawaiian, and Caucasian ancestry. Mammograms from breast cancer cases and from healthy controls were compared using a computer-assisted method of mammographic density assessment. From 1991 to 1997, 935 cases of breast cancer were diagnosed at Kaiser Permanente in Hawaii; for 647 (69%) subjects, a control woman matched by ethnicity, year of mammogram, and age was identified. Conditional multiple logistic regression was applied to estimate the relative risk of developing breast cancer. Breast cancer risk was associated with percent densities and with the size of the dense areas. Women in the category with the most densities experienced a twofold risk of developing breast cancer as compared to women with the least densities. Adjustment for risk factors reduced the strength of the association. Odds ratios were of similar magnitude in Asian women as in Caucasian/Native Hawaiian women, but they were not statistically significant. The results of this study indicate that the associations of breast cancer risk with the magnitude of the dense areas and with the percent densities are of similar strength in women of different ethnicities although density levels vary by ethnicity.

An investigation of soy intake and mammographic characteristics in Hawaii

This cross-sectional investigation in Hawaii explored the relation between soy foods and mammographic characteristics using two food frequency questionnaires and a computer-assisted density assessment method. Japanese and Chinese women reported significantly greater soy food intake than Caucasian women. Whereas soy intake and the size of the dense areas were not related, soy intake and percent mammographic densities were positively associated. The size of the entire breast and the nondense area (ie the fatty part of the breast) were inversely related to soy intake. These results suggest the hypothesis that soy foods by themselves or as part of an Asian dietary pattern may affect the growth of the female breast before adulthood, but the possible mechanisms of action have to be explored in future studies.

Ethnicity and conditional breast cancer survival in Hawaii

The conditional survival experience of 4502 female breast cancer cases diagnosed in Hawaii between 1960 and 1983 was studied. The calculation of conditional survival is based on patients who have already survived for a specified time period. Cox proportional hazards models were used to examine the effect of ethnicity, stage at diagnosis, and menopausal, marital, and socioeconomic statuses on conditional survival prognosis. Native Hawaiian and Filipino women showed a significantly higher risk of dying from breast cancer than any other ethnic group, followed by Chinese and Caucasian women, while Japanese women had the lowest risk. The ethnic pattern of breast cancer survival changed and ethnic survival differences decreased from 17 to 4% as time progressed. Conditional survival varied greatly with stage at first diagnosis. For localized, regional, and distant disease, the conditional survival rate increased from 92, 71, and 24% after diagnosis to 95, 85, and 65% 5 years after diagnosis, respectively, indicating that stage at diagnosis becomes less important in determining survival as time progresses. Being married and of a high socioeconomic status increased survival probability. These results suggest that considering time effect, the conditional survival rate is an informative tool to assess clinical outcome of breast cancer among ethnic groups over a long follow-up period.