Abstract P1-08-07: Risk factors for high-grade and low-grade DCIS in the cancer prevention study-II nutrition cohort
Authors: Puvanesarajah S , Gapstur SM , Gansler T , Patel AV , Gaudet MM 
Published: May 2019

Abstract
Background: Nuclear grade, believed to be established early in carcinogenesis, is an indicator of ductal carcinoma in situ (DCIS) prognosis. Women with high-grade DCIS have a higher risk of local recurrence compared to women with low-grade DCIS. Risk factors for DCIS overall are well-characterized but risk factors by grade are not. Given the prognostic capabilities of grade for DCIS, it is of interest to identify whether risk factors by DCIS grade differ.
Methods: Among 75,630 women enrolled in the Cancer Prevention Study-II Nutrition Cohort in 1992-1993, we identified 422 who were diagnosed with low-moderate grade DCIS (i.e. grades 1 or 2) and 355 who were diagnosed with high-grade DCIS (i.e. grade 3) during follow-up through 2013. Beginning in 1997, biennial questionnaires were administered to update exposure status, including screening mammography in the previous two years. For this analysis, these questionnaires were used to partition follow-up time into approximately two-year intervals. Because screening is strongly linked to diagnosis of DCIS, contribution of person-time within a specific interval was conditional on reporting a screening mammogram in the interval prior. Multivariate joint Cox proportional hazards regression models were used to estimate adjusted hazard ratios (HR) and 95% confidence intervals (CI) for the associations of known breast cancer risk factors with DCIS overall, and with high-grade and low-grade DCIS individually.
Results: Parity (HR=0.70; 95% CI: 0.63-0.78, parous vs. nulliparous), smoking status (HR=0.69; 95% CI: 0.58-0.82, current vs. never smoking) and menopausal status (HR=0.79; 95% CI: 0.73-0.87, natural menopause &lt;50 years vs. natural menopause ≥ 50 years) were inversely associated with risk of DCIS overall. Whereas, positive family history of breast cancer (HR=1.46; 95% CI: 1.36-1.57), personal history of benign breast disease (BBD) (HR=1.73; 95% CI: 1.62-1.85), and current use of combination estrogen and progestin hormone replacement therapy (HR=1.15; 95% CI: 1.04-1.28) were associated with higher risk of DCIS. In analyses stratified on DCIS grade, history of BBD was more strongly associated with higher risk of low-grade (HR=2.21; 95% CI: 1.81-2.70) than with high-grade DCIS (HR=1.29; 95% CI:1.04-1.60) (p for heterogeneity=0.001). Current combination estrogen and progestin hormone replacement therapy use was associated with a higher risk of high-grade DCIS (HR=1.40; 95% CI:1.03-1.90) but not low-grade DCIS (HR=1.02; 95% CI: 0.75-1.40), but the difference by grade was not statistically significant (p=0.5).
Conclusions: In this study, which is the first to comprehensively assess risk factors by DCIS grade, the association between personal history of BBD and risk of DCIS appeared to differ by grade. Due to limited power for some risk factor analyses, future studies using larger prospective cohorts or pooled data should be conducted to better identify these associations.
Citation Format: Puvanesarajah S, Gapstur SM, Gansler T, Patel AV, Gaudet MM. Risk factors for high-grade and low-grade DCIS in the cancer prevention study-II nutrition cohort [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-08-07.