Abstract OT2-4-01: A prospective study of glycoprotein 88 GP-88 blood test in healthy women with Gail model risk &lt;=1.66 undergoing screening for breast cancer (BC) with mammography (MM)
Authors: Tkaczuk Katherine HR , Campassi Cristina , Kesmodel Susan , Bellavance Emily , Olson John , Nichols Elizabeth , Feigenberg Steven J , Yue Binbin , Hicks David , Serrero Ginette 
Published: May 2015

Background: In the US, the majority of BC is diagnosed by screening XRAY mammography (MM) but up to ∼20% of BC are undetected by MM. The development of reliable, blood-based BC screening test to increase the sensitivity and specificity of currently existing BC screening methods such as MM.

Rationale: GP88 is expressed & secreted by BC cells & is not expressed by normal mammary epithelial cells. Two retrospective randomized multi-site trials (one training study & one validating study with about 300 cases each) have demonstrated that elevated GP88 expression in ER+ IDC was statistically correlated with a 4-fold increase in the risk of 5-yr disease recurrence. Multivariate analysis showed that GP88 as a risk predictor was independent from PR expression, tumor size, grade, lymph node status & disease stage. The quantitative GP88 EIA developed to determine the amount of GP88 in biological fluids was developed at A&G. The assay is highly specific for GP88 & both sensitive & linear over a wide dynamic range, i.e. detection of GP88 concentrations from 0.1 to 20ng/ml. A baseline (28.4 ± 5 ng/ml) was established for healthy volunteers (HV). In BC pts a statistically significant increase of serum GP88 was seen for early stage pts (40.7 ± 16 ng/ml; p=0.007). Additionally, a stratification of pts according to their clinical outcomes shows that pts having no evidence of disease (NED) have serum GP88 levels within the range of HV. These data suggest that pts with breast tumors express & secrete high levels of GP88.

Objectives: 1. To determine prospectively GP-88 blood levels in HV at average risk of developing BC who are undergoing screening MM & in women with biopsy-confirmed BC. 2. To establish the statistical distribution of GP88 serum levels in these women by baseline BIRAD classification (1-6). 3. To determine if baseline GP88 level is predictive of change in BIRADS classification from baseline to 12-mos follow-up. 4. To determine if baseline GP88 level is predictive of the appearance of BC at 12 mos follow-up in HV who were cancer-free at baseline.

Inclusion Criteria: Female, aged &gt;=40 yrs old, presenting to UM Breast Center for screening MM or for diagnostic MM or diagnostic workup and/or biopsy due to BIRADS 0 MM at an outside facility &lt;= to 12 wks; Gail model assessment of risk of developing BC&lt;=1.66.

Study procedures: Serum levels of GP88 in subjects with average BC risk factors will be measured prospectively at baseline; 3-6 mos & 6-12 mos. & correlated with BIRADS reading of the screening MM, BIRADS 1 or 2 (benign), BIRADS 3 (short term MM follow-up) & BIRADS 4 or 5 (suspicious and tissue diagnosis needed immediately). GP88 blood level will be correlated with pathologic results of breast biopsies performed on subjects with suspicious BIRADS (4 & 5) MM & final pathologically confirmed diagnosis of BC as BIRADS 6.

Statistical Considerations The total number of pts will be 725 & screened up to 1400 subjects. Study is UM IRB approved & just started accruing. Funding is provided by Maryland Industry Partnership Grant (MIPS)& Avon Grant No. 02-2013-018. Contact: Ntait@umm.edu.

Citation Format: Katherine HR Tkaczuk, Cristina Campassi, Susan Kesmodel, Emily Bellavance, John Olson, Elizabeth Nichols, Steven J Feigenberg, Binbin Yue, David Hicks, Ginette Serrero. A prospective study of glycoprotein 88 GP-88 blood test in healthy women with Gail model risk &lt;=1.66 undergoing screening for breast cancer (BC) with mammography (MM) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr OT2-4-01.