Background: New drugs and technology are primary drivers of health care costs, but their marginal benefit is questionable, particularly in patients with incurable cancer. We examined trends in population-based treatment following diagnosis for metastatic colon and rectal cancer in elderly adults. Methods: We used the Surveillance, Epidemiology, and End Results (SEER) – Medicare linked database to identify persons aged 65 and older diagnosed with distant stage colon (N=16,086) and rectal cancer (N=4,003) between 2000 and 2009. For each year, we report the percent of patients who received cancer directed surgery, chemotherapy, antiemetics/premedications related to the chemotherapy, and hematopoietic growth factors, and the mean cost of care. All estimates are adjusted for patient characteristics, SEER region, survival, and year of diagnosis. Results: The percent of patients who had cancer directed surgery declined 12 and 11 percentage points for colon and rectal cancer patients, respectively. The percent of patients who received chemotherapy increased from 41% to 46% for colon patients and from 52% to 57% for rectal patients. Chemotherapy treatment intensified from 2000 to 2009, with longer duration in chemotherapy and more agents given. Over a third of colon and rectal cancer patients received three or more agents in 2009, often including oxaliplatin and/or bevacizumab. The percent of patients who received hematopoietic growth factors rose appreciably from 4% to 19% for colon patients and from 6% to 21% for rectal patients. Antiemetics/premedication use increased approximately 20 percentage points for all patients. Total costs of care rose from a mean of $61,171 to $74,567 per colon patient and from $68,213 to $82,031 per rectal patient. The percentage of costs due to hospitalizations declined for colon (56% to 47%) and rectal (47% to 40%) cancer patients. Conclusions: The use and intensity of chemotherapy, along with cost of care, for patients with advanced cancer increased markedly from 2000 to 2009. The inclusion of newer more expensive agents shifted the bulk of treatment costs from hospitalizations to the outpatient setting. The value of these treatments for advanced stage elderly patients is unknown.