Preliminary results from a phase II study comparing sunitinib alone or with stereotactic body radiotherapy (SBRT) for newly diagnosed oligometastatic renal cell carcinoma.

4533 Background: Although SBRT has become an option for oligometastatic renal cell carcinoma (oligoRCC), current trials supporting SBRT haven’t been adequately persuasive given their single-arm, non-first-line design. Our study aimed to explore if SBRT improves oncologic outcomes compared with standard first-line systemic therapy in oligoRCC. Methods: This an open-label, double-arm phase II controlled trial enrolling treatment naïve oligoRCC patients (pts), defined as ≤ 5 metastatic lesions (ChiCTR1800017136). No liver or brain metastasis was allowed. Nephrectomy was mandatory before enrollment. Pts were allocated 1:1 to receive either sunitinib alone (control arm) or sunitinib plus SBRT (SBRT arm). Sunitinib was started as 50 mg daily for 4 weeks, followed by 2 weeks off treatment. SBRT was delivered to all metastatic sites within 2 months after sunitinib initiation, with 35-50Gy in 5 fractions. Primary endpoint was objective response rate (ORR); secondary endpoints were disease control rate (DCR), progression-free survival (PFS), overall survival (OS) and safety. Data from pts with ≥ 1 year of follow-up were reported this time. Results: Starting in 2018, the trial has currently completed its accrual, with 48 pts enrolled. Forty-two pts had ≥ 1 year of follow-up and were evaluable for the present analysis. Pt characteristics for SBRT and control arms: median age 51 vs 59 years (p=0.094); synchronous metastasis 31.8% vs 10.0% (p=0.179); clear cell carcinoma 77.3% vs 80.0% (p=1.000); IMDC low or intermediate risk 86.4% vs 80.0% (p=1.000); solitary metastasis 45.5% vs 25.0% (p=0.167). Thirty-four sites received SBRT, most frequently to bone (61.8%) and soft tissue (17.6%) metastasis. The 1-year local control rate after SBRT was 93.8%. ORR (81.8% vs. 25.0%, p=0.000) and DCR (90.9% vs. 60.0%, p=0.047) were significantly higher in SBRT arm than those in control arm. The 1y-PFS was 72.7% for SBRT arm and 35.0% for control arm (HR 0.33, 95% CI 0.16-0.69, p= 0.003). And the 1y-OS was 95.5% for SBRT arm and 80.0% for control arm (HR 1.06, 95% CI 0.31-3.67, p=0.923). Grade 3-4 treatment-related AEs occurred in 66.7% and 62.5% pts in SBRT arm and control arm (p=0.763), respectively. SBRT-related Grade 3-4 toxicity included radiation enteritis (n=1, grade 3) and radiation pneumonitis (n=1, grade 3). Conclusions: Our results showed promising efficacy and acceptable toxicity of SBRT plus sunitinib when compared with sunitinib alone for oligoRCC. Complete results are awaited in 2023 after follow-up completion of the entire cohort. Clinical trial information: ChiCTR1800017136.