Observation prior to systemic therapy in patients with metastatic renal cell carcinoma in the kinase inhibitor era.

4630 Background: Patients with metastatic renal cell carcinoma (mRCC) are heterogenous, with significant variation in clinical course. The use of vascular endothelial growth factor receptor (VEGFR) and mammalian target of rapamycin (mTOR) kinase inhibitors has dramatically changed the prognosis for these patients. However, these treatments are non-curative, necessitating chronic therapy. There is a cohort of patients with indolent disease in whom the initiation of systemic therapy is often deferred. It is inferred that the planned deferment of systemic therapy does not negatively impact on clinical benefit, but there is a lack of published data in the ‘kinase inhibitor era’ to support this contention. Methods: This was a retrospective study. Patients with mRCC treated with sunitinib who had a planned period of observation prior to the initiation of systemic therapy because of asymptomatic or slowly progressive disease were analysed. The primary objective was to determine the progression free survival (PFS...