A Prospective Study of Stereotactic Body Radiation Therapy in Oligometastatic Renal Cell Carcinoma

Abstract

Purpose: Metastasis-directed therapy for oligometastatic renal cell carcinoma (RCC) with stereotactic body radiation therapy (SBRT) has been shown to improve progression-free survival (PFS) and delay time to systemic therapy. Here, we present long-term follow-up of a prospective trial.

Methods and materials: Patients with oligometastatic or recurrent RCC (1-5 lesions, with no therapies in prior month) were enrolled on a pilot study (NCT02542202). SBRT was delivered to all sites (preferred regimen of 50 Gy in 5 fractions). The primary endpoint was the rate of grade 4+ adverse events, and secondary endpoints included local failure, distant progression, and PFS. Exploratory endpoints included time to subsequent systemic therapy and time to subsequent metastasis-directed therapy.

Results: Fifteen patients (all with resected primary tumors, 40% prior systemic therapy, 47% International Metastatic RCC (Renal Cell Carcinoma) Database Consortium intermediate risk) received SBRT to 23 lesions (median, 1; range, 1-4; median BED₁₀ (_{Biologically Effective Dose, α/β=10}) of 100 Gy; 43% lung, 35% abdomen, 17% bone, 4% head and neck). The trial was closed early due to slow accrual. At a median follow-up of 4.8 years, there were no grade 3+ adverse events (AEs) and no late grade 2+ AEs. Five (33%) patients experienced 7 acute grade 2 AEs. Two-year PFS was 46% (90% CI, 24%-65%). At 5 years, cumulative incidence of local failure was 6.7% (90% CI, 0.8%-22%), distant progression was 85% (90% CI, 60%-95%), subsequent systemic therapy was 54% (90% CI, 31%-73%), and subsequent metastasis-directed therapy was 52% (90% CI, 22%-76%). The median time to subsequent systemic therapy was 2.6 years.

Conclusions: Multisite SBRT in oligometastatic RCC offers excellent local control with a low risk of severe late toxicity. This study supports an approach to treat limited metastatic disease with SBRT to delay additional systemic therapy. A subset of patients may benefit from additional, repeated ablative local interventions.