Abstract Background: Primary systemic therapy (PST) is an accepted alternative to adjuvant systemic therapy of breast cancer. It provides equivalent survival, increased breast conservation rates, and prognostic information. Methods: This analysis assesses patterns of PST use based on information collected by the National Cancer Database (NCDB), a joint project of the American College of Surgeons and the American Cancer Society which captures data on over 70% of all diagnosed breast cancer patients in the U.S. Using the b-participant use file of the NCDB, we evaluated regional, patient, and tumor factors associated with PST use. Results: The NCDB captured 621,319 patients treated with PST from 2006 to 2010. Of these, 7.4% received systemic therapy pre-operatively, and 3.6% in both the pre- and post-operative settings. Factors correlating with timing of therapy are shown in the table. PST use increased steadily from 7.0% to 7.8% (p<0.001) from 2006 to 2010. PST was significantly more frequently used in younger, African-American, Hispanic, low-income, uninsured patients with larger, node positive tumors, living in large metropolitan areas in the West and treated in academic centers. These factors remained significantly and independently associated with PST on multivariate analysis. UnivariateMultivariateFactorPre-opPost-opBothp-valuep-valueYear of Diagnosis <0.001<0.00120067.0%90.0%3.0% 20077.1%89.5%3.4% 20087.2%89.2%3.6% 20097.6%88.6%3.8% 20107.8%87.7%4.5% Region <0.001<0.001Northeast5.7%90.9%3.4% Atlantic6.7%90.4%2.9% Southeast8.0%88.2%3.8% Great Lakes6.5%90.1%3.4% South7.7%88.4%3.9% Midwest5.2%90.2%4.6% West11.4%84.2%4.4% Mountain8.8%88.7%2.5% Pacific7.7%88.3%4.0% Community type (pop): <0.001<0.001Metro (>1M)7.9%88.3%3.8% Metro (250K-1M)7.1%89.5%3.4% Metro (<250K)6.3%90.5%3.2% Urban, adjacent to a metro area (20K+)6.5%90.0%3.5% Urban, not adjacent to metro (20K+)6.3%90.5%3.2% Urban, adjacent to metro (2500-19,999)6.7%89.4%4.0% Urban, not adjacent to metro (2500-19,999)6.0%90.6%3.4% Rural/urban pop, adjacent to metro (<2500)6.0%90.3%3.8% Rural/urban pop, not adjacent to metro (<2500)5.7%90.5%3.8% Facility type: <0.001<0.001Community program6.4%90.5%3.1% Comprehensive community program7.1%89.5%3.5% Academic/research8.4%87.4%4.2% Other6.4%90.0%3.6% Age: <0.001<0.001<609.4%85.8%4.8% ≥604.9%92.9%2.3% Race: <0.001<0.001Caucasian6.7%89.3%3.5% African-American11.8%83.3%4.9% Other8.4%87.5%4.1% Ethnicity: <0.001<0.001Non-Hispanic7.2%89.3%3.6% Hispanic11.2%83.3%5.4% Median household income: <0.0010.023<$30K9.0%86.8%4.2% $30K-$34,9997.7%88.6%3.7% $35K-$45,9997.2%89.1%3.7% $46K+6.9%89.6%3.4% Insurance: <0.001<0.001Uninsured15.3%78.1%6.6% Private7.8%88.3%3.9% Medicaid13.7%79.2%7.2% Medicare4.8%93.0%2.2% Military8.2%87.5%4.4% Clinical T stage: <0.001<0.001T12.4%96.4%1.2% T213.6%79.5%6.9% T3-T435.9%45.3%18.8% Clinical N stage: <0.001<0.001N04.8%92.9%2.3% N1-326.0%60.3%13.7% pop: population; multivariate OR and 95% CI not shown Conclusion: PST appears to be underutilized, received by only 7.8% of all patients, 36% of T3-T4 tumors, and 26.0% of clinically node positive patients. However, its rate of use has increased over the past years. There is also significant regional variation in the use of PST, independent of patient and tumor factors. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-14-02.