Site Both <1% 1–5 6–10 >10 Toronto <1% 1–5 6–10 >10 Kingston <1% 1–5 6–10 >10 BMC Cancer 2008, 8:130 http://www.biomedcentral.com/1471-2407/8/130 Table 3: Association between PR in nonneoplastic tissue and breast cancer status, by study site Cells staining for PR (%) Crude OR (95% CI) Age-adjusted OR (95% CI) Controls Cases N 36 109 109 65 20 70 62 48 16 39 47 17 (%) (11.3) (34.2) (34.2) (20.4) (10.0) (35.0) (31.0) (24.0) (13.4) (32.8) (39.5) (14.3) N 38 63 62 43 22 27 31 21 16 36 31 22 CI, confidence interval; OR, odds ratio; PR, progesterone receptor. in situ only, controls with atypical ductal hyperplasia, sub- jects whose slides contained no TDLU, or subjects using exogenous hormones would not change the conclusions made from these analyses. The percentage of nonneoplastic epithelial cells staining positively for PR was not significantly differentially related to ER positive breast cancer status as compared to ER negative breast cancer (p = 0.67). It was, however, sig- nificantly differentially related to PR positive breast cancer status as compared to PR negative breast cancer among subjects from Toronto (p = 0.03). Although PR levels in nonneoplastic tissue were not related to PR positive breast cancer status, levels of PR in nonneoplastic tissue above 1% were associated with reduced odds of having PR neg- ative breast cancer status (results not shown). The same trend was seen among subjects from Kingston, but it was not statistically significant (p = 0.19). Interaction between ER and PR in nonneoplastic tissue and breast cancer status Levels of ER and PR in nonneoplastic breast tissue were positively correlated. The partial Spearman correlation (adjusted for age) was rs = 0.36 in Toronto controls, rs = 0.42 in Kingston controls, rs = 0.50 in Toronto cases, and r = 0.65 in Kingston cases. In Kingston, the odds of being s a breast cancer case with respect to ER levels was qualita- tively higher in women in whom PR levels were higher (Table 4). The interaction, however, was not statistically significant in either site (p > 0.34). Discussion After age was taken into account, very little association remained between ER levels in nonneoplastic tissue and (18.5) 1.0 (30.6) 0.5 (0.3–1.0) (30.1) 0.5 (0.3–0.9) (20.9) 0.6 (0.3–1.1) (21.8) 1.0 (26.7) 0.4 (0.2–0.7) (30.7) 0.5 (0.2–1.0) (20.8) 0.4 (0.2–0.9) (15.2) 1.0 (34.3) 0.9 (0.4–2.1) (29.5) 0.7 (0.3–1.5) (20.9) 1.3 (0.5–3.3) Site Both <1% 1–5 6–10 >10 Toronto <1% 1–5 6–10 >10 Kingston ≤10% 11–33 >33 1.0 0.7 (0.4–1.2) 0.8 (0.4–1.4) 0.7 (0.4–1.3) 1.0 0.5 (0.2–1.1) 0.9 (0.4–2.0) 0.4 (0.2–1.0) 1.0 1.0 (0.4–2.4) 0.8 (0.3–1.8) 1.4 (0.5–3.6) breast cancer status. The odds of having the highest level of ER were higher in breast cancer cases than biopsy con- trols only in Kingston, one of our two study sites. Some indication of an inverse association between PR levels in nonneoplastic tissue and breast cancer status was observed among subjects from Toronto, which was largely because of the association of PR levels with PR negative breast cancers; no association between PR levels in nonne- oplastic tissue and breast cancer status was observed among subjects from Kingston. Table 4: Joint association between both ER and PR in nonneoplastic tissue and breast cancer status, by study site Cells staining for ER ≤5% >5% Cells staining for PR 1.0 1.0 0.5 (0.2–1.3) 1.8 (0.6–5.9) 1.4 (0.6–3.3) 1.9 (0.6–5.7) 1.1 (0.5–2.5) 2.6 (0.9–7.6) p(interaction) = 0.29 1.0 1.0 0.6 (0.2–1.6) 1.9 (0.6–6.2) 1.4 (0.5–3.9) 1.3 (0.4–4.5) 1.6 (0.4–5.7) 1.6 (0.4–5.9) p(interaction) = 0.34 1.0 1.0 0.9 (0.3–2.6) 1.2 (0.4–3.9) 1.1 (0.4–2.8) 3.1 (0.9–10.3) p(interaction) = 0.69 ER, estrogen receptor; PR, progesterone receptor. Page 6 of 9 (page number not for citation purposes)