GCDFP-15 blood levels for stratification of risk of breast cancer development in women with active breast gross cystic disease

The risk of developing breast cancer has been shown to be elevated in women with breast gross cystic disease (GCD) confirmed by aspiration of breast cyst fluid. The GCDFP-15 protein is a major component protein of breast GCD fluid. The protein is secreted by apocrine metaplastic cells lining micro and gross cysts of the breast. It is also a constituent protein secreted by normal apocrine glandular systems, and it is present in approximately 50% of breast carcinomas. Blood levels of GCDFP-15 are measurable in the low ng/ml range in normal individuals. A proportion of patients with metastatic breast cancer have high circulating blood levels up to 70000 ng/ml. This study evaluated the relationship between blood levels of GCDFP-15 in women with active breast gross cystic disease, demonstrated by breast cyst aspiration, and the risk of breast cancer development. A group of 135 patients who had active breast gross cystic disease demon strated by cyst aspiration, also had a concomitant blood level of GCDFP-15 determined. The patients have been subsequently followed for an average of 10.1 years and assessed for risk of breast cancer development. Twelve of these women have developed breast carcinoma and two have died of unrelated causes. For the 72 women who clinically developed fewer than 10 aspirated cysts, the relative risk of breast cancer was 1.8 if their highest GCDFP-15 plasma level was in a normal range (less than 40 ng/ml) versus a relative risk of 4.2 if the GCDFP-15 plasma level was elevated. This difference was more pronounced for the 63 women in this study with 10 or more total aspirated cysts, where the relative risk for breast cancer development was 2.0 for women with normal range GCDFP-15 plasma levels versus 7.1 for those with elevated plasma levels. Our data indicate that GDCFP-15 blood levels may be useful in identifying groups of women with active breast gross cystic disease who are at increased risk of developing breast cancer.