Outcomes from second-line therapy in long-term responders to first-line tyrosine kinase inhibitor in clear-cell metastatic renal cell carcinoma

Background: Although sequential targeted therapy is standard in patients with metastatic clear-cell renal cell carcinoma (m-ccRCC), the choice of drugs and optimal administration sequence have yet to be established. The objective of this study was to explore whether it is preferable to rechallenge a long-term responder to a first-line tyrosine kinase inhibitor (TKI) with a TKI or whether to switch to a mammalian target of rapamycin inhibitor (mTORi); to determine whether second-line treatment response depends on duration of first-line response (TD1). Patients and methods: Retrospective multicenter study (2004-2011) of 241 consecutive mRCC patients (clear-cell histology) who received a first-line TKI for >= 6 months followed by a second-line TKI (n = 118) or mTORi (n = 123). End points: Progression-free survival (PFS) and time-to-treatment failure (TTF) on second-line therapy. Multivariable full-model: second-line drug, TD1, ECOG-PS before first-and second-line, best objective response (first-line), Fuhrman grade, number of metastatic sites, and presence of bone metastases. Adjustment covariable: International mRCC Database Consortium (IMDC) risk score. Multiple propensity score and missing data methods were used. Any correlation between first-line and second-line PFS was investigated using censored quantile regression models (CQRM). Results: Sequence effect in the overall cohort was in favor of the TKI-TKI sequence over the TKI-mTORi sequence on using TD1 as continuous covariable (HR approximate to 0.75 for PFS and TTF). TKI-TKI superiority was attributed in large part to the 11-22 month (TD1) subgroup of patients which displayed significantly better outcomes [HR approximate to 0.5; median PFS (months): 9.4 (5.9-12.2) versus 3.9 (3.0-5.5), P = 0.003; TTF(months): 8.0 (5.5-11.0) versus 3.6 (3.0-4.6), P = 0.009]. Upon full CQRM, long-term second-line responders were more likely to have received a second TKI than an mTORi and to have been long-term responders to first-line TKI. Conclusions: m-ccRCC patients who remained on first-line TKI between 11 and 22 months benefited from a TKI rechallenge rather than from second-line mTORi.