Background

Blood banks have large altruistic donor populations and existing infrastructure that make them attractive sites for genetic epidemiologic research, but donors' willingness to participate and the impact on blood donation are unknown.

Study design and methods

A total of 2162 blood donors in Northern California responded to a cross-sectional questionnaire in August and September 2007. Participants were asked their likelihood of participation and future blood donation under three different scenarios: identity-linked genetic research, identity-unlinked genetic research, and genetic testing as a service.

Results

The majority of blood donors indicated that they would be likely or very likely to participate in identity-linked genetic research (67%) and in identity-unlinked genetic research (54%). While older donors and more frequent donors were more likely to participate in identity-linked research, younger, Caucasian, more educated, and more frequent donors were more likely to participate in identity-unlinked research. Less than 10% of donors indicated they would be less likely to donate blood in the future if genetic research was conducted at blood banks. More than 75% of donors would be interested in genetic testing as an optional service at the blood bank, but more than 20% of donors would be less likely to donate if such a service was offered.

Conclusion

Overall, we found that the majority of blood donors would be likely to participate in genetic research and that less than 10% would be less inclined to donate if such research was conducted by blood banks.

Background

Though mammographic density (MD) has been proposed as an intermediate marker of breast cancer risk, few studies have examined whether the associations between breast cancer risk factors and risk are mediated by MD, particularly by tumor characteristics.

Methods

Our study population included 3392 cases (1105 premenopausal) and 8882 (3192 premenopausal) controls from four case-control studies. For established risk factors, we estimated the percent of the total risk factor association with breast cancer that was mediated by percent MD (secondarily, by dense area and non-dense area) for invasive breast cancer as well as for subtypes defined by the estrogen receptor (ER+/ER-), progesterone receptor (PR+/PR-), and HER2 (HER2+/HER2-). Analyses were conducted separately in pre- and postmenopausal women.

Results

Positive associations between prior breast biopsy and risk of invasive breast cancer as well as all subtypes were partially mediated by percent MD in pre- and postmenopausal women (percent mediated = 11-27%, p ≤ 0.02). In postmenopausal women, nulliparity and hormone therapy use were positively associated with invasive, ER+ , PR+ , and HER2- breast cancer; percent MD partially mediated these associations (percent mediated ≥ 31%, p ≤ 0.02). Further, among postmenopausal women, percent MD partially mediated the positive association between later age at first birth and invasive as well as ER+ breast cancer (percent mediated = 16%, p ≤ 0.05).

Conclusion

Percent MD partially mediated the associations between breast biopsy, nulliparity, age at first birth, and hormone therapy with risk of breast cancer, particularly among postmenopausal women, suggesting that these risk factors at least partially influence breast cancer risk through changes in breast tissue composition.