1772 LESS THAN 50% OF ONE MONTH RELATIVE DOSE INTENSITY IS THE POOR PROGNOSTIC FACTOR OF SORAFENIB THERAPY FOR CYTOKINE REFRACTORY RENAL CELL CARCINOMA

IVC thrombus ( Level II) was assessed for radiographic responses in thrombus size and location. We then described the pre and posttreatment characteristics of these patients. RESULTS: In the 25 patients meeting our inclusion criteria, pre-therapy biopsy showed clear cell RCC in 19 and unclassified RCC in 6. Prior to initiation of targeted therapy, the tumor thrombus level was II in 18 (72%), III in 5 (20%) and IV in 2 (8%). The targeted therapy was Sunitinib in 12 cases and a combination of other agents in the remaining 13. Median duration of therapy was 2 months (range 1 to 9). Following systemic therapy, 7 (28%) had a measureable increase in the thrombus height above the renal vein, 7 (28%) had no change and 11 (44%) had a decrease. The mean change of the thrombus height was 0.6cm, median 0cm ( 8.5 to 5), and the mean change of the thrombus diameter was 0.3cm, median 0.1cm ( 1.6 to 0.9). The change in the tumor thrombus level classification after therapy was: 1 patient (4%) had an increase, 21 (84%) had stable thrombi and 3 (12%) had a decrease. In only 1 case (4%) the surgical approach was potentially affected by thrombus regression (level IV to III). Regression resulting in a change in the clinical level of the tumor thrombus was only seen in patients treated with Sunitinib. Yet, the change in thrombus height, diameter or clinical level classification between Sunitinib and non-Sunitinib patient cohorts did not reach statistical significance (Table). No statistically significant predictors of tumor thrombus response to targeted therapy were found. CONCLUSIONS: Targeted therapy had minimal clinical effect on RCC tumor thrombi. Only patients treated with Sunitinib had measurable thrombus regression; however, the magnitude of this effect on the thrombus between the two groups was not statistically significant and is of unclear clinical relevance.