Apparent DNA adducts of 4-ABP were detected by IHC at very
high frequency (100%) in 55 adjacent non-tumor tissues of breast
cancer cases from women participating in the Long Island Breast
Cancer Project (28). 4-ABP adducts were also frequently detected
(28%) by 32P-post-labeling in human milk samples from women residing
in Little Rock, AR (26). In contrast, our subjects harbored no
adducts of 4-ABP, when assayed by LC-ESI/MS/MS3. Our observed
rate of 0/70 is statistically significantly different from the rate of 28%
(18/64) and 100% (55/55) noted in the two published studies, respectively.
The upper 95% confidence limit of our observed rate is,4%. It
is of note that the cases in the present study are comparable in age and
ethnicity distributions to those in the Houston (27) and Long Island
studies (28,43). Our subjects were 96% non-Hispanic whites with
a median age of 50 years. In the Houston study, 78% of the subjects
were non-Hispanic whites with a median age of 43 years (27) and
94% of the subjects in the Long Island Breast Cancer Project were
non-Hispanic whites with a median age of 59 years (28,43). Age and
ethnicity were not reported in the Little Rock study (26).