Controversies in renal cell carcinoma: Treatment choice after progression on vascular endothelial growth factor-targeted therapy

The mammalian target of rapamycin inhibitor (mTORI) everolimus and the tyrosine kinase inhibitor (TKI) axitinib are the only two post-first-line treatment options for metastatic renal cell carcinoma (mRCC) licensed at present. Extrapolation of robust phase III studies suggests that median progression-free survival (PFS) is similar between agents. This presents a dilemma for the physician planning treatment for their patients with mRCC: should they be treated with a TKI–mTORI or a TKI–TKI sequence? The lack of direct comparison between axitinib and everolimus leaves the clinician without clear guidance on the optimal choice in second-line therapy. In phase III studies, both post first-line everolimus and axitinib have been shown to delay disease progression; however, cumulative toxicity with sequential use of TKIs may result in more treatment interruptions or dose reductions or increased likelihood of adverse events. While everolimus exerts a tolerability advantage, axitinib is associated with higher response rate and a similar PFS benefit. Proven superiority cannot be used to guide treatment sequence selection in mRCC. Instead, therapeutic planning requires us to take a long-term view of our patient’s treatment that includes quality of life and a balance between symptom control, adverse event management and avoidance of unnecessary drug interruptions or dose reductions. In the absence of curative therapies, sustaining a patient’s quality of life is a major goal throughout the course of treatment and choosing a second-line agent that is able to adequately achieve this by limiting adverse events should be a priority.