Abstract P6-09-05: No evidence of association between mammographic breast density and risk of breast cancer in women with atypical hyperplasia
Authors: Vierkant RA , Degnim AC , Hartmann LC , Frank RD , Radisky DC , Visscher DW , Frost MH , Winham SJ , Ghosh K , Vachon CM 
Published: May 2016

Abstract
Background
Women with atypical hyperplasia (AH) are at an approximately four-fold increased risk of subsequent breast cancer (BC). Mammographic breast density (MBD) is a well-established risk factor for BC, but its contribution to BC risk in women with AH remains an open question. We previously reported no association between MBD [measured by Wolfe's parenchymal pattern (PP)] and BC risk in a cohort of 147 women with AH. Here, we present results in an expanded cohort of 459 women diagnosed with AH between 1985 and 2001.
Methods
The Mayo Clinic Benign Breast Disease Cohort includes 13,485 women who had benign core and/or excisional biopsy 1967-2001. Biopsy tissues were reviewed by our study pathologist to determine presence of AH. MBD was available from clinical records starting in 1985, coded as PP (the standard for 1985-1996) or BI-RADS (1997-2001) density criteria. The original four-level PP (N1-fatty, P1-ductal prominence &lt;25% of breast, P2-ductal prominence &gt;25%, DY-dysplasia) and BI-RADS (fatty, scattered densities, heterogeneously dense, extremely dense) measures were re-categorized as low, moderate or high MBD by combining the middle two categories for each. BC events and clinical information were obtained by questionnaires, medical records and the Mayo Clinic Tumor Registry. Women were followed from benign biopsy to date of BC, death or last contact. Standardized incidence ratios (SIRs) were generated overall and within subgroups defined by density measure (PP vs. BI-RADS), number of atypical foci, and BMI by dividing the observed number of BCs by population-based expected values. Cox regression was used to estimate MBD hazard ratios after adjustment for demographic and clinical variables.
Results
Of the 551 women diagnosed with AH between 1985 and 2001, 459 (83%) had MBD data within 1 year prior to biopsy. Of these, 68 (15%) had low, 221 (48%) had moderate, and 170 (37%) had high MBD, respectively. Over a median follow-up of 11.7 years, 80 BCs were observed. SIRs for breast cancer did not differ significantly across density categories, overall or within any subgroups examined (see Table). Cox regression adjusting for age, BMI and density measure (PP vs. BI-RADS) also failed to identify an association with MBD (p=0.55).
Low MBDModerate MBDHigh MBD N / BCsSIR (95% CI)N / BCsSIR (95% CI)N / BCsSIR (95% CI)P-valueOverall68/123.5 (1.8,6.1)221/393.6 (2.5,4.9)170/293.4 (2.3,4.8)0.97MBD Measure PP59/113.6 (1.8,6.5)85/153.0 (1.7,5.0)130/243.3 (2.2,5.0)0.87BI-RADS9/12.7 (0.1,14.7)136/244.0 (2.6,6.0)40/53.4 (1.1,7.9)0.90No. Atypical Foci 147/62.3 (0.9,5.1)123/182.8 (1.7,4.4)96/163.5 (2.0,5.8)0.63214/47.5 (2.0,19.1)58/134.8 (2.6,8.3)41/62.5 (0.9,5.5)0.213+7/26.7 (0.8,24.0)40/84.4 (1.9,8.6)33/74.0 (1.0,8.2)0.83BMI &lt;2525/21.5 (0.2,5.4)75/184.9 (2.9,7.7)101/173.4 (2.0,5.5)0.1625-2919/54.9 (1.6,11.3)68/92.8 (1.3,5.2)36/42.1 (0.6,5.4)0.4530+23/54.8 (1.6,11.2)76/123.0 (1.6,5.3)32/74.0 (1.6,8.2)0.67SIRs compare observed numer of BCs to expected using Iowa SEER data. Analyses account for the effects of age and calendar period. P-value is test of heterogeneity in SIRs across columns.
Conclusions
We found no evidence of an association between MBD and subsequent BC in women with AH.
Citation Format: Vierkant RA, Degnim AC, Hartmann LC, Frank RD, Radisky DC, Visscher DW, Frost MH, Winham SJ, Ghosh K, Vachon CM. No evidence of association between mammographic breast density and risk of breast cancer in women with atypical hyperplasia. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-09-05.