Abstract P6-05-12: Prognosis of subtypes of the mucinous breast carcinoma in Chinese women: A population-based study of 32-year experience (1983-2014)

Background: The heterogeneous nature of the mucinous breast cancer (MBC), with its subtypes of pure (PMBC) and mixed carcinoma (MMBC), calls for more precise individualized prognosis assessment. PMBC showed favorable prognosis in both Chinese and Caucasian women, with nodal status and TNM stage as the prognostic predictors [PMID: 18026874, 22451233]. However, few studies had investigated tumor biology and prognosis of MMBC in Chinese population, especially with respect to the different co-existing cancer components. Methods: From January 1983 to December 2014, 197 consecutive MBC patients, including 117 PMBC and 80 MMBC, received breast cancer surgery in Peking Union Medical College Hospital. The clinicopathological characteristics, treatment choice, disease-free survival (DFS) and overall survival (OS) were compared both between PMBC vs MMBC, and among subgroups of MMBC according to the mixed entities, including 24 women with ductal caricinoma in situ (DCIS) and 45 with IDC. Univariate and Cox multivariate analyses were performed to identify the prognostic factors. Results: The 197 MBC comprised 1.9% of contemporary 10,192 breast cancer (BC). Compared to PMBC, MMBC had significantly more lymph node metastasis (p=0.038), Her2 positivity (p=0.036), high Ki-67 index (defined as >20%, p=0.026) and anti-Her2 targeted therapy (p=0.006). All these differences remained significant when the comparison were performed among PMBC, MBC+DCIS and MBC+IDC, and additional significant difference were identified in tumor size (p=0.036), pTNM stage (p=0.003) and chemotherapy (p=0.003). However, no significant difference was found in DFS or OS between any two subtypes/subgroups of MBC, including PMBC, MMBC, MBC+DCIS and MBC+IDC. High Ki-67 index (p=0.046) appeared to be the significant DFS related prognostic factor for PMBC, whereas estrogen receptor (ER) status (univariate p=0.000, multivariate p=0.062) and immunophenotype (luminal, her2, or triple-negative, univariate p=0.000, multivariate p=0.079) might be the potential DFS predictors for MMBC. None of the above-mentioned clinicopathological factors could serve as OS predictors for MBC. Conclusion: This population-based study showed that there were significant difference in nodal status, Ki-67, Her2 positivity and targeted therapy between PMBC and MMBC, and furthermore in tumor size, stage and chemotherapy among PMBC and subgroups of MMBC such as MBC+DCIS and MBC+IDC. However, survival outcomes were similar between these clinical entities and subgroups, suggesting the intra-tumoral heterogeneity might not interfere with survival outcomes of MBC in Chinese woman. High Ki-67 index was identified as the significant DFS related prognostic factor for PMBC, whereas ER status and immunophenotype as the potential DFS predictors for MMBC. Citation Format: Yao R, Pan B, Sun Q, Zhou Y, Mao F, Lin Y, Guan J, Wang X, Zhang Y, Zhang X, Shen S, Zhong Y, Xu Y, Shi J, Zhu Q, Cai F, Liang Z. Prognosis of subtypes of the mucinous breast carcinoma in Chinese women: A population-based study of 32-year experience (1983-2014). [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 P6-05-12.