A growing number of retrospective and prospective studies with the ESTRAMET^TM 2/16 kit for urinary 2- and 16a-hydroxyestrone {19} have shown that this test accurately measures changes in estrogen metabolism.

Changes in estrogen 2/16 metabolism may be associated with a risk for cancer, and other estrogen-related diseases. Several early prospective studies with the ESTRAMET^TM 2/16 kit suggested that the 2/16 ratio might be significantly reduced in women with cervical {20} and breast cancer {21}. It was further demonstrated that the 2/16 ratio was readily modified by dietary factors such as consumption of broccoli {22}. More recent, studies support an association between breast cancer and a reduction in the 2/16 ratio.

In a case-control study,  Kabat et al, {23} found that postmenopausal women with a 2/16 ratio below 1.38 had a multivariate adjusted odds ratio of 33 for breast cancer risk, whereas those with a 2/16 ratio between 1.38-1.90 had an odds ratio for breast cancer of 10.  Analyses of the individual metabolites indicated that urinary 16a-hydroxyestrone was also a strong risk factor.

The study of Luo et al, {21}and Ho et al, {24} was a case-control study of 101 Chinese women, comprising 65 breast cancer patients, and 36 controls. These investigators found that the profile of urinary estrogen metabolites was distinctly altered in breast cancer patients. Multiple linear regression analysis showed that the odds ratio of breast cancer for women with higher 2/16 (>0.9) was 0.1, or one-tenth that of those with 2/16<0.9. This significant difference was seen for both pre- and postmenopausal women. Controls were randomly selected from women who were confirmed to have benign breast disease by histology of breast biopsies.

The predictive value of any test is expected to be  greatest in-groups with the highest prevalence of the condition or disease detected by the test.  This is also the case for the 2/16-ratio test which may be indicated by several studies of estrogen metabolism in African-American women. Taioli et al. reported that African-American women had significantly lower ratios of urinary estrogen metabolites 2/16 compared to Caucasian women {25}. Taioli has linked altered metabolism to the MSP-1 genetic polymorphism of the CYP1A1 gene found in this group {26}, and has shown that women with this genetic lesion can not normally induce 2-hydroxylated estrogens {27}. The CYP1A1 gene encodes the protein cytochrome P450 1A1 that is responsible for oxidative 2-hydroxylation of estradiol and estrone. These findings have been subsequently supported by the study of Coker et al, {28}.  In this study, African-American women had significantly lower 2OHE1/creatinine levels than Caucasian women, and this ethnic difference held within case-control groupings and among premenopausal and postmenopausal groupings. In agreement with other studies, breast cancer patients were significantly more likely to have lower 2/16 ratios than control subjects (p=0.008) after adjusting for race, age, and menopausal status. Part of this ethnic difference in estrogen metabolism was found to be due to ethnic differences in body mass. These findings may explain, in part, the higher mortality and stage at clinical presentation of breast cancer in African-American women, and present the possibility of altering disease risk and outcome in this group by altering estrogen metabolism.