Outcomes in patients with metastatic renal cell carcinoma (mRCC) who complete 18 months of first-line IO-TKI therapy: A conditional survival analysis from the IMDC.

e16528 Background: Immuno-oncology and tyrosine kinase inhibitor (IO-TKI) combinations are standard first-line (1L) treatments for mRCC. The characteristics and long-term outcomes of patients who successfully complete a defined treatment period are not well described. Methods: Using the International Metastatic Renal Cell Carcinoma Database Consortium (IMDC), we identified patients treated with 1L IO–TKI combinations (Pembrolizumab Axitinib, Pembrolizumab Lenvatinib, Nivolumab Cabozantinib, and Avelumab Axitinib). We compared baseline characteristics between patients who were still on IO treatment at 18-months and those who were not. Conditional survival was calculated as the probability of subsequent survival from 18-months onward. Overall survival (OS) and time to next treatment (TTNT) were analyzed. Patients with ongoing treatment for less than 18-months were excluded. Results: Of 953 patients treated with 1L IO-TKI, 424 (44.5%) were still on treatment at 18-months. Patients in the 18-month landmark group in univariable analysis were more likely to be younger (p < 0.001), have favorable IMDC risk (37.7% vs 22.0%, p < 0.001), better performance status (PS) (PS 0: 66.8% vs. 45.6%, p < 0.001), have undergone nephrectomy (77.2% vs. 59.2%, p < 0.001), and less likely to have liver metastasis (14.0% vs 21.3%, p = 0.005) and bone metastasis (28.7% vs 36.7%, p = 0.012). In multivariable analysis, better PS (PS 1 vs 0: OR 0.62, p = 0.06; PS ≥2 vs 0: OR 0.19, p = 0.01) and nephrectomy (OR 2.27, p = 0.007) were independently associated with a higher likelihood of completion. For patients who reached 18-months, the median subsequent OS from that landmark was an additional 73.1 months (95% CI 69.2-NR), and the median subsequent TTNT was an additional 30.3 months (95% CI 24.0-40.9). In contrast, the median OS from treatment initiation for patients who did not reach the 18-month landmark was 20.9 months. A similar pronounced survival advantage was observed for patients who reached a 24-month treatment landmark. Conclusions: In this real-world cohort, almost half of mRCC patients treated with 1L IO-TKI reached an 18-month IO treatment landmark. This group had more favorable baseline characteristics, with good PS, and prior nephrectomy being clinical predictors of completion. The conditional survival analysis demonstrates that patients who were under treatment for more than 18-months enjoyed an exceptionally favorable long-term prognosis, which is important for prognostication and patient counseling. Conditional Survival; Probabilities are calculated using landmark as time 0. Probability of surviving additional year(s) from landmark Treatment duration >= 18m Treatment duration >= 24m OS probability at 1 year 93% 95% 2 years 82% 82% 3 years 72% 73% 4 years 64% 70% 5 years 60% 68% TTNT probability at 1 year 76% 76% 2 years 56% 59% 3 years 44% 47% 4 years 36% 38%