Tumor shrinkage during VEGF inhibitor therapy as an independent predictor of PFS and OS in renal cell carcinoma (RCC)

423 Background: Response to VEGF targeted therapies has been recently shown to be an important prognostic and predictive marker in metastatic RCC. However, whether the extent of tumor shrinkage (TS) correlates with distinct clinical outcome remains unknown. We investigated the role of early TS fractions on median progression free survival (PFS) and median overall survival (OS).

METHODS: Tumor evaluations according to RECIST 1.1 were performed within 3 months (mo) of targeted therapy with a VEGF inhibitor in 108 patients (pts). Pts were then categorized in fractions of TS: a) -100% to -60%; b) -60 % to -30% and c) -30% to 0% or gain in tumour size: d) 0% to +20% and e) > +20%. Kaplan-Meier and log-rank analyses were performed to estimate PFS and OS with a landmark set to 6 mo. Multivariate Cox proportional hazard model was utilized for evaluation of prognostic factors.

RESULTS: First-line VEGF inhibition achieved a PFS of 10.6 mo (95% CI 8.7 - 12.5) and an OS of 29.8 mo (95% CI 23.9 - 35.6) in all pts. 5 pts achieved a complete remission (4.6%), 28 pts a partial remission (25.9%), 52 pts. stable disease (48.2%), and 23 pts. had progressive disease (21.3%) as best response. In univariate analyses histology (clear cell differentiation vs. others) and TS were associated with PFS (p = 0.026; p <0.0001) and OS (p = 0.017; p = 0.009). Multivariate analyses confirmed the relevance of TS as a prognostic variable for OS (p = 0.021; HR 1.49) and PFS (p = <0.001; HR 1.91).

CONCLUSIONS: TS is an independent predictive and prognostic marker in first-line treatment with VEGF inhibitors in mRCC. [Table: see text].