Background: In the phase 3 METEOR study (NCT01865747), cabo improved OS (median 21.4 vs 16.5 mo; HR, 0.66; 95% CI, 0.53–0.83), progression-free survival and objective response rate compared with eve in patients (pts) with previously treated advanced RCC (Choueiri 2016). Retrospective studies have shown that early tumour shrinkage (eTS), based on target lesion reduction from baseline to first post-baseline scan, has predictive value for targeted therapies in RCC (Grunwald 2015; Grunwald 2016); here we evaluate its impact on OS in METEOR. Methods: In total, 658 pts were randomized 1:1 to receive cabo (60 mg qd) or eve (10 mg qd), stratified by MSKCC risk group and number of prior VEGFR TKIs. Target lesion size was assessed by independent radiology review using CT/MRI scans at baseline, every 8 wk for the first 12 mo and every 12 wk thereafter. Median OS was estimated for pts with ≥30% eTS, any eTS or no eTS at first post-baseline scan (week 8); data cutoff, 2 October 2016 (Motzer 2018). Results: Median follow-up was 28 mo (IQR 25, 30). Median (range) time to objective response was 1.91 (1.6, 11.0) mo with cabo and 2.14 (1.9, 9.2) mo with eve, and corresponded to the time to the first post-baseline scan. A greater proportion of pts had ≥30% eTS with cabo (20%) than with eve (5%) and the rate of any eTS was higher in the cabo arm (73%) than with eve (47%; Table). Median OS with cabo vs eve for pts with ≥30% eTS was not reached (NR; 95% CI, 23.7–NR) vs 10.2 mo (95% CI, 3.9–NE), respectively (stratified HR, 0.45; 95% CI, 0.21–0.95; p<0.05). Median OS with cabo vs eve for pts with any eTS was 23.7 (95% CI, 21.7–27.7) vs 17.3 mo (95% CI, 15.4–20.8), respectively; (stratified HR, 0.62; 95% CI, 0.48–0.80; p<0.05). OS was similar for cabo and eve for pts with no eTS. Conclusions: Cabo demonstrated a higher rate and greater magnitude of eTS at first post-baseline scan compared with eve, and eTS was associated with prolonged OS in pts treated with cabo. Clinical trial information: NCT01865747

^aFrom baseline to first post-baseline scan (week 8)