Abstract B95: In four Midwest tribes there are few significant differences in the screening adherence of higher- and lower-risk women
Authors: Petersen Wesley O. , Nicometo Ann M. , Vierkant Robert , Roubidoux Marilyn , Haugen Steven , Kaur Judith S. 
Published: June 2012

Purpose: The study has two related purposes. To: 1. describe breast cancer risk factors and screening patterns in a sample of American Indian and Alaska Native (AI/AN) women from four tribes in the Northern Plains region; and 2. ascertain associations between women's risk factors and their adherence to mammographic screening guidelines with the intention of using the results to develop future interventions to increase screening, especially in higher risk non-adherent women.

Background: The Indian Health Service (IHS) has noted that challenging economic factors make increases in AI/AN women's screening participation difficult. In this light, understanding the relationship between risk factors and screening adherence is an important first step in developing low-cost 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 high 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. We hypothesized that women at higher risk as compared to women at lower risk on the factors analyzed would be more likely to adhere to annual screening guidelines promoted by their clinics.

Procedures/Methods: Criteria for inclusion in this study were: women with no history of breast cancer who were ≥ 40 years of age, and had at least one mammogram on file. We reviewed the charts of a representative sample of ∼20% of eligible women in four tribes (1250 records, 1088 of of which met inclusion criteria). The study collected Gail Model risk factor data and also assigned BIRADS scores to an early and late mammogram where they were available (888 pairs) for each woman. In addition, we collected age at menopause as an additional risk factor. 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 of 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, using standard criteria, 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 1.5 years (18 months) were considered adherent. Results are age-adjusted for each tribal site and across sites.

Summary of Findings: Only P-values for older age at menopause (0.02), older chronological age (0.005), and 5-year Gail Model risk scores (0.02) were consistent with our hypotheses that women at higher risk would be more adherent with screening guidelines. There was no significant association between screening adherence and life-time risk (0.12), family history (0.28), age at menarche (0.99), age at first live birth (0.68), biopsy history (0.99), or BIRADS density scores (0.16).

Conclusions: The minimal relationship between risk factors and adherence suggests that generally neither individual risk factors nor overall risk predict women's 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 2011;20(10 Suppl):B95.