Clinicopathological features and prognosis of rare carcinomas of the breast: A comparative analysis from the NCDB.

Abstract

e19256 Background: A comparative analysis of the clinicopathological features, immunohistochemistry, and overall (OS) for rare ( < 10%) of all breast cancers (BCs) has not been widely explored. Methods: The National Cancer Database (NCDB) was reviewed for patients with a confirmed diagnoses of the following rare BC tumors: Mucinous adenocarcinoma (MuC), tubular adenocarcinoma (TuC), intraductal micropapillary (IMP), papillary carcinoma (PaC), and intraductal papillary adenocarcinoma (IPA) between 2010 and 2016. Patients with an unknown stage were excluded. Univariate analyses & multivariable Cox-regression models were performed in SAS v. 9.4. Results: Analysis included 70,341 patients. MuC was the most common histologic type seen among the rare tumors in our cohort n = 30,087 (43%), compared with 9,681 (13.8%) TuC, 12,735 (18.1%) IMP, 435 ( < 1%) PaC, & 17,403 (24.7%) IPA. TuC & IMP both presented earlier in life, with a median age of 60 versus 69 years for MuC patients and 67 years for both PaC & IPA. The majority of carcinomas were ER+/PR+/HER2- (MuC 88.6%, TuC 89.9%, IMP 67.3%, PaC 76.8%, & IPA 79.6%); ER+/PR+/HER2+ were noted in 3.5% of Muc and 13.2 % of IMP, and ER-/PR-/HER2- were seen in PaC 8.7% and IPA 7.3%. Two highly significant factors for inferior outcome were stage (III & IV) and metastasis to the brain. Stage ≥3 at diagnosis conferred a worse prognosis for MuC patients (HR 3.1, p < 0.0001), IPA patients (HR 3.5, p < 0.0001), & IMP patients (HR 4.8; p < .0001) when compared to patients with stage 0 & 1. Brain metastasis was an adverse mortality indicator for MuC patients (HR 2.4, p < .0003), IPA patients (HR 6.8, p < 0.0001), & IMP patients (HR 10.4, p < .0001). For MuC, age ≥60 was also prognostic (HR 2.7; p < .0001). The 5-year OS was 92.2% for patients with MuC, 94.7% for TuC patients, 93.1% for IMP patients, 81% for PaC & 90% for IPA overall (p-values < 0.0001). Conclusions: The rare BC tumors analyzed in this large database confirm that these tumors are typically seen at an older age, are commonly ER+/PR+/HER2 -, and rarely HER2 + or Triple negative. Mucinous adenocarcinoma being the most common type. They have an overall good prognosis, with papillary carcinoma having inferior OS. Other poor prognostic factors include older age, brain metastasis and advanced stages at diagnosis.