BMC Cancer (2001) 1:8 http://www.biomedcentral.com/1471-2407/1/8 Table 2: Breast cancer risk factors by estrogen receptor status. Factor Weight (kg) by quartile <58 58-64 65-71 >71 Number of full term pregnancies 0 1 >1 Hormone replacement-therapy Never Ever Estrogen receptor positive Adjusted OR (95% p trendb CI)a Estrogen receptor negative Adjusted OR (95% p trendb CI) 1.0 ref.c 0.7 (0.5-1.5) 1.1 (0.7-1.8) 1.2 (0.7-1.9) 1.0 1.0 (0.6-1.6) 0.6 (0.4-0.9) 1.0 1.1 (0.7-1.7) >0.20 0.01 1.0 1.3 (0.5-3.6) 1.9 (0.7-4.9) 2.1 (0.8-5.9) 1.0 1.7 (0.6-5.1) 1.2 (0.5-3.1) 1.0 1.8 (0.8-4.1) 0.10 >0.20 a Odds ratio, 95% confidence interval, age-adjusted; b two sided p-value for linear trend in OR's, c reference category. The median duration of follow up with regard to death of all causes was 7.2 years; a total of 125 breast cancer pa- tients died. The overall breast cancer survival was related to tumor size, degree of spread, and stage of disease (data not shown). These prognostic indicators were significantly associated with breast cancer tumors that were ERN (ta- ble 3). Table 3: Over all breast cancer survival in relation to clinical char- acteristics and stage of disease by estrogen receptor status. Estrogen receptor posi- tive Adjusted RR (95% CI)a Estrogen receptor neg- ative Adjusted RR (95% CI) Characteristic Tumor size (mm) <50 1.0 ref.b ≥ 50 0.7 (0.2-3.0) Metastatic lymph nodes 0 1.0 ≥ 1 1.6 (0.9-2.7) Stage of disease Early 1.0 Advanced 1.5 (0.9-2.6) 1.0 5.4 (1.8-15.9) 1.0 4.6 (1.7-12.3) 1.0 6.0 (2.1-16.9) a Relative risk of dying, 95% confidence interval, adjusted for age at diagnosis; b reference category. Women with the highest serum concentration of dieldrin had a more than seven-fold increased risk of developing an ERN breast cancer compared to women with the low- est concentration, and the risk increased in a stepwise fashion with increasing dieldrin exposure level. No asso- ciation could be observed for the ERP tumors (table 4). The frequency of large tumors (size >50mm) at the high- est dieldrin quartile exposure group was 27.3% (average size, 37 mm) and 8.7% (average size, 27 mm) for ERN and ERP tumors, respectively. The corresponding fig- ures for spread of disease was 61.5% and 45.8%. For the remainder of the organochlorine compounds, ORs for the highest exposure level tended to be higher for women who developed an ERP breast cancer than those who had an ERN tumor, though none of the relation- ships reached statistical significance (table 4). In gener- al, the risk of dying among women with the highest organochlorine exposure level was higher among women with ERP than ERN breast cancers, but the only statisti- cal significant relationship was observed for ΣPCB (table 5). A statistically significant inverse trend was seen for exposure to HCB and ΣPCB in women with ERN tumors. Exposure to dieldrin was associated with a significant in- creased risk of dying for women with ERP tumors in the second and third quartile compared to the first quartile. An approximately 2-fold not significant increased risk of dying among women in the highest dieldrin exposure level compared to the lowest was observed for both ERP and ERN tumors (table 5). Similar results were obtained in analyses on a subgroup of 80 cases, where it was pos- sible to adjust for tamoxifen therapy (data not shown).