e14644 Background: A retrospective analysis published in June 2004 suggested that patients who received intravenous calcium/magnesium (CaMg) were less likely to experience oxaliplatin-induced neuropathy. Randomized, placebo-controlled trials were developed to test whether CaMg was indeed neuroprotective in patients receiving oxaliplatin. In July 2007, an early Data Monitoring Committee report for one of these trials (CONcePT) described lower response rates in patients randomized to CaMg. However, in March 2008, a revised report negated that claim. In February 2011, publication of a subsequent placebo-controlled study (N04C7) supported that CaMg was possibly neuroprotective, but presentation of a more definitive placebo-controlled trial (N08CB) in June 2013 provided convincing evidence that CaMg does not reduce oxaliplatin-associated neuropathy. Methods: Monthly rates of CaMg the same day as oxaliplatin therapy were assessed using administrative claims data from a large United States (US) health plan. The individuals covered by this health plan, about 88 million between 2003-2013, are geographically dispersed across the US, with the greatest representation in the South and Midwest. We identified receipt of oxaliplatin and CaMg using Healthcare Common Procedure Coding System codes on the claims from 2003 through October 2013. Results: 33,147 patients were included from the health plan. Peaks and valleys in rates of use of CaMg when oxaliplatin was given over the past decade are presented in Table. Conclusions: Substantial swings in CaMg use occurred over time. Prescribing patterns appeared highly sensitive to presentation of study results, suggesting that new scientific evidence was translated into clinical practice in a timely manner. However, some might view these practice changes as premature given that none of the early reports provided conclusive data. Use of CaMg in US claims data. Date % of oxaliplatin doses given with CaMg May 2003 0% May 2007 41% May 2008 5% May 2012 32% Oct 2013 6%