Physician Liver Function Test (LFT) Monitoring for Tykerb Pts

In July 2008, the lapatinib (Tykerb) Prescribing Information (label) was updated to include a boxed warning related to hepatotoxcity and detailed instructions for monitoring liver function before and during lapatanib exposure. For patient safety, it is of interest to know the extent to which providers are adherent with these guidelines for hepatic monitoring of lapatanib users. Thus, the aim of this study is to determine if physicians conduct liver function testing prior to prescribing lapatanib and at regular intervals during exposure, and if they withdraw lapatanib, and do not re-treat, for patients who demonstrate severe liver enzyme elevations while exposed. These aims will be tested in the "Pre-label" (prior to the boxed warning) and "Post-label" (after the boxed warning) periods to determine if physician adherence to the guidelines changed as a result of the warning. Specifically, the boxed warning provided the following guidance: "Hepatotoxicity (alanine transaminase or aspartate transaminase \>3 times the upper limit of normal and total bilirubin \>1.5 times the upper limit of normal) has been observed in clinical trials (\<1% of patients) and postmarketing experience. The hepatotoxicity may be severe and deaths have been reported. Causality of the deaths is uncertain. The hepatotoxicity may occur days to several months after initiation of treatment. Liver function tests (transaminases, bilirubin, and alkaline phosphatase) should be monitored before initiation of treatment, every 4 to 6 weeks during treatment, and as clinically indicated. If changes in liver function are severe, therapy with lapatanib should be discontinued and patients should not be re-treated with lapatanib" The following objectives will be assessed and compared among patients prescribed lapatanib before and after the addition of detailed guidance on liver function testing to the product label on July 9, 2008: 1. Objective 1: Determine if physicians perform liver funtion tests (LFTs)