Abstract 5645: Associations between biomarkers and outcome in a patient cohort with invasive lobular carcinoma
Authors: Rachel C. Jankowitz, Kevin Levine, Maryam Zamanian, Matthew Sikora, Nilgun Tasdemir, Priscilla McAuliffe, David Dabbs, Nancy Davidson, Brenda Diergaarde, Steffi Oesterreich
Journal: Cancer Research (2017)

Abstract Invasive lobular carcinoma (ILC) represents only 5-15% of all breast cancer. However, if it were an independent cancer type, it would rank as the sixth most common cancer in women, as common as non-Hodgkin lymphoma or melanoma. ILC is chronically understudied as a breast cancer subtype, but compared to invasive ductal carcinoma (IDC) ILC is more often HR-positive, HER2-negative, and lower histologic grade. Despite these favorable tumor characteristics, recent studies suggest outcome in ILC is not consistent with these favorable characteristics. We herein describe our single institution experience with ILC. Using cancer registry data, we identified 709 women over the age of 18 (including 85 with recurrences) diagnosed at our institution between 1990 and 2011 with HR-positive, early-stage (I-III), primary ILC and potentially available banked tissue samples. We implemented a case-cohort design to investigate molecular tumor characteristics associated with ILC prognosis. Patients were excluded for a history of synchronous bilateral breast cancer at the time of diagnosis, a prior history of invasive breast cancer, or a diagnosis of non-breast malignancy within 5 years prior to their diagnosis of ILC. Originally, a sample of 200 subjects was selected for further study and molecular characterization. However, tissue acquisition, subject eligibility and verification of recurrences yielded a sample of in total 131 subjects (including 33 with recurrences), and the case-cohort design was recreated for this final sample. All available information regarding patient and tumor characteristics, treatment history, and outcome was collected from medical records. ER, PR, and Ki67 protein (IHC) and RNA (Nanostring analysis) levels were analyzed with respect to outcome of patients. PR H-score, but not ER H-score, was significantly associated with survival in our overall ILC cohort. In the case-cohort analysis there was a weak correlation between ER, PR and Ki67 RNA levels (measured by nanostring) and ER, PR and Ki67 protein levels (measured by IHC) in the ILC tumor samples. After the Nanostring data was normalized, box plots were constructed for ESR1, PR and MKI67 so that a simple t-test could look at gene expression in recurrences and non-recurrences. There was no significant difference in ER expression between non-recurrences and recurrences. The recurrence cases had significantly lower PR expression levels. We will present quantitative ER and PR data, as well as detailed clinical characteristics for this cohort in relation to outcome. Citation Format: Rachel C. Jankowitz, Kevin Levine, Maryam Zamanian, Matthew Sikora, Nilgun Tasdemir, Priscilla McAuliffe, David Dabbs, Nancy Davidson, Brenda Diergaarde, Steffi Oesterreich. Associations between biomarkers and outcome in a patient cohort with invasive lobular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5645. doi:10.1158/1538-7445.AM2017-5645