Abstract B106: Breast cancer screening among American Indian/Alaska Native (AI/AN) women: Adherence and risk factor associations in four Bemidji area tribes
Authors: Petersen Wesley O. , Nicometo Ann M. , Roubidoux Marilyn A. , Vierkant Robert A. , Haugen Steve , Kaur Judith S. 
Published: December 2010

Purpose: The purpose of this study was to describe breast cancer risk factors and screening patterns in a sample of American Indian and Alaska Native (AI/AN) women from four tribes within the Bemidji Area of the Indian Health Service (Northern Plains region), and to ascertain the association between risk factors and adherence to mammographic screening guidelines. The IHS has noted that economic factors make increases in screening participation difficult. In this light, understanding the relationship between risk factors and screening adherence is an important first step in developing interventions to improve screening participation, especially for women at higher risk of breast cancer. Lending importance to the role of screening in reducing breast cancer deaths in Northern Plains AI/AN women are rates of later stage (regional or distant disease) diagnoses that are equal to the Non-Hispanic White (NHW) population (95.8 and 95.4/100,000 respectively). Later stage at diagnosis is associated with worse survival profiles.

Procedures/Methods: Criteria for inclusion in this study were: ≥ 40 years of age, at least one mammogram on file, and no history of breast cancer. We reviewed the charts of 20% of eligible women in four tribes (1190 records). The study collected Gail Model risk factor data and also assigned BIRADS scores to at least one mammogram for each woman. For each Gail Model risk factor (age, age at menarche, age at first live birth, number of first degree relatives with a breast cancer history, breast biopsy, number of biopsies, history or atypical hyperplasia), women were assigned to higher or lower risk categories by comparison with calculated scores for women of the same age. Overall five-year and lifetime Gail Model risk scores also were calculated for each woman and compared with predicted risk for women of equivalent ages. For breast density, women were determined to be at lower risk if their BIRADS score was 1 or 2, and at higher risk if they were scored 3 or 4. To ascertain levels of screening adherence, we followed American Cancer Society (ACS) guidelines which recommend an annual mammogram beginning at age 40. We used this standard because it is the recommendation given to women in the clinics where the study was conducted. All women who received screening exams within 1.2 years (14.4 months) were considered adherent.

Summary of Findings: There was no significant difference between overall Gail Model 5-year risk scores of Bemidji Area AI/AN women and the predicted scores. Bemidji Area women have a significantly lower lifetime risk than what is predicted. For individual risk factors, high screening adherence was significantly associated only with chronological age (p = 0.04) and history of biopsy (p =0.02). There was no significant association between screening adherence and BIRADS density scores.

Conclusions: Absence of a relationship between risk and adherence, which is low generally, suggests that women are not using their individual risk factors or their overall risk to guide their screening decisions. This suggests that personal and clinic-centered mediators should be identified to guide future interventions to increase the proportion of women who adhere to screening guidelines, especially women who are at greater risk.

Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):B106.