Abstract Background: Breast cancer care imposes a significant financial burden to U.S. healthcare systems and has become a key focus in the health care debate. Therapies for breast cancer are expensive, and the economic burden of these therapies may be rising due to the rapid introduction of pricey new drugs and techniques. There are limited data on the health care costs of individuals with breast cancer after initial diagnosis and how these costs have changed over time. Methods: We conducted a retrospective analysis of commercially insured adult women with newly diagnosed non-metastatic breast cancer (identified via previously published claims-based algorithms) using 2007-2016 data from a large US health plan available in OptumLabs® Data Warehouse. We included patients with continuous health plan coverage for at least 2 years after initial diagnosis 2007-2014 and assessed how total health care spending and out-of-pocket costs (paid amounts) changed over this time. Costs were adjusted to 2016 US dollars using the general Consumer Price Index. Inpatient, outpatient, and outpatient pharmacy costs were evaluated. A multivariable logistic regression model was used to examine predictors of above average cost (cost > mean for that year of diagnosis). Results: A total of 12,446 newly diagnosed breast cancer patients were identified (mean age, 51.6 years). Forty percent had undergone mastectomy, 38% chemotherapy, and 63% radiation. After adjustment for inflation, total healthcare costs increased 29.7% from 2007 to 2014 (Table 1), with increases primarily observed during the first year after diagnosis. Out-of-pocket costs remained relatively stable, and accounted for 5.3% of the total spending. Approximately 80% of the total costs were related to care received in the outpatient setting. Factors independently associated with above average spending included treatment with mastectomy [OR 1.78 (95% CI 1.5-2.1)], reconstruction [OR 3.0 (95% CI 2.6-3.5)], radiation [OR 4.0 (95% CI 3.4-4.7)] and chemotherapy [OR 18.4 (95% CI 16.6-20.3]. Table 1.Average healthcare spending over time Mean cost during first year after diagnosisMean cost during second year after diagnosisYear of diagnosistotalout-of-pockettotalout-of-pocket2007$80,296.17$4,271.25$16,559.21$1,907.012008$84,126.70$4,445.78$16,785.43$2,205.982009$88,331.45$4,728.42$17,005.68$2,214.932010$91,502.58$5,067.78$17,243.91$2,126.192011$93,826.40$5,089.45$16,862.45$2,027.962012$96,690.06$5,449.91$17,814.09$2,179.262013$104,064.93$5,678.19$17,087.47$2,115.972014$104,169.74$5,620.51$16,714.12$1,590.67 Conclusions: Breast cancer care is increasingly expensive during the first year after diagnosis, and costs are greatest for the recipients of more aggressive treatments. Costs during the second year after diagnosis have remained relatively stable. Citation Format: Ruddy KJ, Sangaralingham LR, Freedman RA, Jemal A, Mougalian SS, Keegan T, Loprinzi CL, Gross CP, Henk HJ, Shah N. Trends in the cost of care for breast cancer among women with commercial insurance [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD6-07.