Background: Despite data on the sensitivity and specificity of serum tumor marker tests, there is no evidence to suggest that early changes in therapy related to rising tumor markers have an effect on survival. Studies have failed to show benefit of surveillance testing in patients with limited disease. We performed a retrospective analysis in patients with advanced cancer to evaluate trends in utilization of tumor marker testing and the associated costs. Methods: Patients at Columbia University Medical Center with advanced or metastatic cancer were identified by ICD9 codes and confirmed with tumor registry and medical record review. Between 7/1/2013-6/30/2014 for each patient, the dates each of the following tumor markers were recorded: alpha fetoprotein (AFP), CA 125, CA 15-3, CA 19-9, CA 27-29 and carcinoembryonic antigen (CEA). Subjects who had > 1 of any single tumor marker over the time-frame were included. We evaluated the maximum number of tests per month and the average number of tests per-month the patient was alive. Costs of each tumor marker were determined using 60% Medicare reimbursement rates. Results: Over the 12 month time frame 996 patients were included in the analysis. The mean number of any individual test per-patient was 7 and the maximum was 35; and the mean number of total tests per-patient was 12 and the maximum was 70. CEA and CA-19-9 were the most commonly ordered tests with an average of 1.94 and 2.18 times per-month, per-patient. On average the number of patients that had > 1 of any individual test per month was 33%. The most common tests were CA-125, CEA and CA-19-9 (25.3%, 38.2% and 45.6% respectively). Overall 21.9% of patient had ≥ 3 of any individual marker per-month (38% CA19-9 and 25.6% CEA). The mean per-patient annual cost of testing was $421, with a maximum $2,567. Costs per-patient were highest for those with breast cancer (mean $755, max $1,787) and pancreatic cancer (mean $643, max $2,567). Conclusions: Tumor marker testing is frequent, with a large number of patients being tested multiple times per month, every month. Given the rising costs of cancer care, the large number of serum tests, and the frequency of use, efforts should be made to determine the clinical utility of tumor marker testing in metastatic cancer patients.