46 Radiological tumor burden is an independent risk factor for survival in patients with metastatic clear cell renal cell carcinoma (mccRCC) treated with first line immunotherapy (IO)-based regimens

Abstract Background IO-based regimens (IO + IO or IO + VEGF inhibitor) represent current standard of care systemic therapies for the management of patients with mRCC. IMDC is the current standard to assess prognosis in patients with mRCC of clear cell histology. Baseline radiological tumor burden (BRTB) is a readily available measurement to calculate using routine CT-scans. Here we describe the utility of BRTB as prognostic factor in patients with mccRCC treated with first line IO-based regimens. Methods We reviewed data of 183 patients with mccRCC treated at Dana-Farber Cancer Institute from August 2014 to October 2023 and who received ≥ 1 dose of an IO-based regimen (IO + IO or IO + VEGF inhibitor). Patients with available CT-scan reports within 1 month prior to first line treatment initiation were included in our analysis. BRTB was assessed by a single operator as the sum of all measurable lesions as listed on the RECIST v1.1 report. The primary outcome was overall survival (OS), and secondary outcomes were time to treatment failure (TTF) and time to next therapy (TTNT). To evaluate the impact of BRTB on OS, TTF and TTNT, we used univariable and multivariable Cox regression models accounting for IMDC risk group, history of nephrectomy, and presence of either bone, liver, or brain metastases prior to first line initiation. Results A total of 150 patients satisfied the inclusion criteria and were included in our final analysis, of which 80% of patients were male (120/150). 9% (13/150) had favorable risk, 51% (77/150) had intermediate risk and 20% (30/150) had poor risk by IMDC criteria. Overall, 73% (109/150) of patients had nephrectomy prior to first line therapy initiation and 41% (61/150) had either brain, bone, or liver metastasis. Median follow-up was 44.8 months. Every 1 cm increase in BRTB was associated with a 5% increase in risk of death (HR: 1.05; 95% CI: 1.03 – 1.08; p < 0.0001). On multivariable analysis, radiological tumor burden was significantly associated with OS (HR: 1.04; 95%CI: 1.00 – 1.08; p = 0.03). After categorizing BRTB by tertiles, tertile 1 included 0 - 7.5 cm, tertile 2: 7.6– 15.3 cm and tertile 3: 15.4 – 47.7 cm. The 4-year OS estimates were 84% (95%CI: 74 – 97%), 60% (95%CI: 45 – 81%) and 43% (95%CI: 29 – 66%), respectively, for the 1st, 2nd and 3rd tertile (log-rank P < 0.0001). BRTB did not show a significant association with TTF on univariable (HR: 1.00; 95%CI: 0.99 – 1.01; p = 0.783), or multivariable analysis (HR: 0.99; 95%CI: 0.97 – 1.01; p = 0.428). As for TTNT, BRTB also did not show a significant association on univariable (HR: 1.01; 95%CI: 1.0 – 1.02; p = 0.234) or multivariable analysis (HR: 1.01; 95%CI: 0.99 – 1.03; p = 0.453). Conclusions Baseline radiological tumor burden is an independent prognostic factor for OS in patients with mccRCC treated with first line immunotherapy-based regimens. However, tumor burden is not significantly associated with TTF or TTNT. Figure: Kaplan-Meier curves representing OS based on baseline radiological tumor burden assessed by RECIST v1.1 (Tertile 1: 0 - 7.5 cm; Tertile 2: 7.6 - 15.3 cm; Tertile 3: 15.4 – 47.7 cm). P value is derived from the log-rank test.