Researchers develop breast cancer risk model for Hispanic women

Issue: December 25, 2015

An absolute risk model based on data from Hispanic women more accurately predicted risk for breast cancer in this population than existing models, according to study results presented at the American Association for Cancer Research conference on The Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved.

However, the model overestimated the risk for breast cancer in foreign-born Hispanic women compared with U.S.-born women and requires further validation studies, according to the researchers.

The NCI’s Breast Cancer Risk Assessment Tool (BCRAT) — which is widely used to estimate risk for invasive breast cancer, counsel women about their risk and design prevention trials — bases its estimates for Hispanic women on data from non-Hispanic white women, according to study background.

“Currently, there is no breast cancer risk-prediction model for Hispanic women,” Matthew P. Banegas, PhD, MPH, an investigator with Kaiser Permanente Center for Health Research in Portland, Ore., said in a press release. “We developed a model based on data on ethnicity, nativity and breast cancer risk factors, as well as incidence and mortality rates in Hispanic women, which allowed us to create a more specific tool to predict their risk for developing invasive breast cancer.”

Banegas and colleagues constructed their model using data from two case-control trials of U.S.- and foreign-born Hispanic women: the San Francisco Bay Area Breast Cancer Study (SFBCS) and the 4-Corners Breast Cancer Study (4-CBCS).

The SFBCS study included data from 1,086 Hispanic women with breast cancer (U.S.-born, n = 533; foreign-born, n = 553) and 1,411 healthy controls (U.S.-born, n = 464; foreign-born, n = 947).

The researchers used these data to separately estimate RRs and attributable risk (AR) based on age at first full-term pregnancy (< 20 years, 20-29 years or ≥ 30 years/nulliparous), age at menarche (≥ 14 years, 12-13 years or < 12 years), history of breast cancer in a first-degree relative and previous biopsy for benign breast disease.

Further, researchers estimated nativity-sensitivity absolute risks by combining RR and AR information from the SFBCS with data on invasive breast cancer incidence and competing mortality rates from the California Cancer Registry and the SEER database.

Researchers used data from the 4-CBCS study (cases, n = 731; controls, n = 836) as a comparison to evaluate the model’s RR feature. They then used data from Hispanic women in the Women’s Health Initiative (n = 6,220) to asses model calibration and discriminatory accuracy.

Risk factors for U.S.-born Hispanic women included age at fist full-term pregnancy (RR = 1.26), biopsy for benign breast disease (RR = 1.1) and family history of breast cancer (RR = 1.18).

For foreign-born women, risk factors included age at first full-term pregnancy (RR = 1.6), age at menarche (RR = 1.3), biopsy for benign breast disease (RR = 1.62) and family history of breast cancer (RR= 2.48).

For a majority of U.S.-born Hispanic women, the risk model estimated lower risk for invasive breast cancer than the BCRAT, whereas foreign-born women had a higher risk prediction using the new model.

The researchers did not observe significant difference between RRs estimated from 4-CBCS and those used in the U.S.-born Hispanic model; however, the RRs of foreign-born women were significantly higher than those from 4-CBCS (P < .05).

The model appeared well-calibrated for U.S.-born Hispanic women (observed to expected ratio [O/E] = 1.07; 95% CI, 0.82-1.4). The model overestimated risk for breast cancer among foreign-born women (O/E ratio = 0.66; 95% CI, 0.41-1.06) in independent data from the Women’s Health Initiative; however, the overestimation only involved 17 cases and did not reach statistical significance.

The discriminatory accuracy of the model appeared modest for both groups (U.S.-born women, area under the curve [AUC] = 0.564; foreign-born women, AUC = 0.625).

The geographic homogeneity of women included in the model’s development may serve as a potential limitation, according to Banegas.

“The goal of our work is to enable Hispanic women to better understand their risk for developing invasive breast cancer,” Banegas said. “They will be able to discuss this information with their physician and what it means for them specifically.” – by Cameron Kelsall

Reference:

Banegas MP, et al. Abstract A09. Presented at: AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov. 13-16, 2015; Atlanta.

Disclosure: The NCI provided funding for this study. Banegas reports no relevant financial disclosures.