Effect of a gene expression-based tissue of origin test's impact on patient management for difficult-to-diagnose primary cancers

459 Background: An important step for a novel test is assessing its clinical utility and real-world effect on diagnosis and patient management. This report describes the results of a survey of physicians who have ordered a gene expression profile assay for identification of tumor tissue of origin (Pathwork Tissue of Origin Test) for patients with difficult-to-diagnose primary cancers. Methods: The IRB-approved registry collects data from participating physicians who have ordered the Tissue of Origin test for their patients. To minimize recall bias, a detailed interview is conducted using both a web-based questionnaire and a confirmatory telephone interview with the physicians. Chart survey includes collection of data on patient demographics, diagnostic procedures including imaging and pathology including immunohistochemistry as well as therapy. The physicians are queried regarding their working diagnoses and treatment recommendations prior to and after Tissue of Origin Test result availability. Results: Enrollment in the registry is ongoing. Fifty-nine patients (34 women) have been studied and 48 participating physicians have completed the interview. Survey results suggest that most patients have undergone extensive evaluation including multiple imaging tests (median, 6) and exhaustive immunohistochemistry (median, 10) prior to gene expression analysis. For these 59 pts, based on clinicopathologic evaluation, physicians reported working diagnoses for 46% of patients prior to test results and 83% after test results. Treatment recommendations were changed for 53% of patients. The majority (70%) of treatment changes were for chemotherapy. Physicians (n=26) reported that the Tissue of Origin test decreased the diagnosis associated anxiety in 62% of patients. Conclusions: This ongoing registry study confirms that in patients with difficult-to-diagnose primary cancers, extensive baseline diagnostics is not uncommon and less than half of the patients have an established working diagnosis. Survey results suggest that the Tissue of Origin Test led to a change in working diagnosis and changed treatment recommendations in over half the patients. [Table: see text]