Racial disparities among women who develop invasive secondary breast cancer.

e18523 Background: Noninvasive breast cancers ( e.g. ductal and lobular carcinoma in situ) are highly treatable nonobligate precursors to invasive breast cancers. However, even after treatment, some women develop second breast cancers (SBCs), increasing their mortality risk. Prognosticators may inform treatment recommendations for women at higher risk of SBC. In this study, risk factors for SBC were evaluated using deidentified data from the Hawaiʻi Tumor Registry (HTR), an NCI SEER registry. The HTR covers a uniquely multiethnic, statewide population allowing for elucidation of disparities in understudied U.S. populations. Methods: Women initially diagnosed between 1973-2017 with noninvasive (ductal and lobular) breast cancer were identified. Patient demographics, cancer characteristics, and treatment information were collected. Univariate (UVA) and multivariate (MVA) logistic regression analyses were used to identify factors associated with SBC, defined as a breast cancer diagnosis > 6 months after their prior cancer. Results: Of 7,057 women diagnosed with a first noninvasive breast cancer, 696 (10%) developed SBC. Invasive ipsilateral (iiSBC) and invasive contralateral (icSBC) disease represented 9% and 20% of patients who developed SBC, respectively. The five most prevalent ethnic groups were Chinese, Filipino, Japanese, Native Hawaiian, and White. When adjusting for confounders, women who developed iiSBC were more likely to be Native Hawaiian (odds ratio [OR] = 3.20, 95% CI = 2.07-4.94) or Filipino (OR = 1.72, 95%CI = 1.02-2.91) when compared to Whites; diagnosed between 1990-1999 (OR = 2.06, 95%CI = 1.27-3.34); and not have undergone surgical treatment (OR = 2.93, 95%CI = 1.42-6.04). Women who developed iiSBC were less likely to be > 50 years old (OR = 0.67, 95%CI = 0.49-0.90); diagnosed between 2010-2017 (OR = 0.18, 95%CI = 0.09-0.35); received lumpectomy with radiation therapy (OR = 0.54, 95%CI = 0.35-0.72); and undergone mastectomy (OR = 0.48, 95%CI = 0.32-0.72). Women who developed an icSBC were more likely to be Native Hawaiian (OR = 1.58, 95%CI = 1.06-2.35) or Filipino (OR = 1.60, 95%CI = 1.06-2.42). These women were also less likely to have been diagnosed between 2010-2017 (OR = 0.30, 95%CI = 0.17-0.53). On a subset analysis separating all patients with SBC by first course treatment type, there were no statistically significant differences for treatment type based on race/ethnicity. Conclusions: Overall, in this observational study, Native Hawaiian women, Filipino women, and younger women had increased odds of developing invasive SBC. This study highlights racial disparities in SBC development risk that was not previously appreciated among disaggregated groups of Pacific Islanders and Asian women when compared to White women. This may help oncologists understand the risk of developing SBC in these understudied populations.