Background: Vascular endothelial growth factor (VEGF)-targeted therapy is administered continuously until progression in metastatic clear cell renal cancer (mRCC). The role of intermittent therapy is under investigation. Preclinical data raise concerns about this approach.
Materials and methods: This study combined the data from three similar phase II studies investigating VEGF-targeted therapy prior to planned nephrectomy for untreated mRCC (European Union Drug Regulating Authorities Clinical Trials 2006-004511-21, 2006-006491-38 and 2009-016675-29). The significance of progression during the planned treatment break (median 4.3 weeks) was assessed.
Results: Sixty-two patients had a structured treatment interruption for nephrectomy after achieving clinical benefit from treatment and restarted therapy. Twenty-three of these patients (37%) progressed (Response Evaluation Criteria In Solid Tumors v1.1) on the first scan after the treatment break. Subsequent stabilisation of disease occurred in 16 of the 23 (70%) progressing patients when the same VEGF tyrosine kinase inhibitor (TKI) was reintroduced. Baseline characteristics, such as the Memorial Sloan Kettering Cancer Centre prognostic score, did not predispose to the development of this progression. Progression during the treatment break was associated with an increased risk of death on multivariate analysis {hazard ratio (HR) 5.56; [95% confidence interval 2.29-13.5], P < 0.01}. Sequential fluorodeoxyglucose positron emission tomography showed a rebound in metabolic activity during the treatment break.
Conclusions: Progression during planned VEGF TKI treatment interruptions is frequent and associated with a poor prognosis. Treatment cessation should be pursued with caution.
Keywords: FDG-PET; VEGF-targeted therapy; intermittent treatment; metastatic renal cancer; nephrectomy.