Outcomes of Targeted Therapy Plus Immunotherapy and High-Dose Stereotactic Ablative Body Radiotherapy (SABR) for Metastatic Renal Cell Cancer Patients

Stereotactic ablative body radiotherapy (SABR) is one of the treatment options for metastatic renal cell carcinoma (mRCC) but is limited by a lack of data to evaluate targeted therapy plus immunotherapy concurrently with high-dose SABR to multiple sites. We evaluated the safety and disease control for mRCC patients who concurrently received the above tri-modality treatment.Patients were treated with SABR (40-70 Gy/5-10 fractions) for small lesions or partial-SABR (tumor center boosted with 6-8 Gy/3-5 fractions with 50-60 Gy/20-25 fractions to the whole tumor volume) for bulky tumors or tumors adjacent to critical organs. When SABR/partial-SABR was not feasible, a moderate fractionated radiotherapy plan, usually 60Gy/20 fractions were applied. of Targeted therapy plus immunotherapy (PD-1 inhibitor) was not interrupted during or after radiotherapy (RT). Adverse events (AEs) were evaluated. Disease control rate (DCR), objective response rate (ORR), progression-free survival (PFS) and overall survival (OS) were calculated. The PFS1 was defined as the first progression since the start of RT. The PFS2 was defined as the second progression after the second RT course, if new metastases occurred after first RT were all re-irradiated, and the systemic therapy was not changed. The Kaplan-Meier method was used for time-to-event endpoints.A total of 51 patients, with a median age of 57 yr, were enrolled. The median follow-up was 12 months. There were 75% of patients with intermediate-risk and 18% with favorable-risk disease. 61% of the patients were oligometastatic. 71% had clear cell renal cancer. There were 241 metastases while 161 (67%) were irradiated. 80% of the lesions received SABRP/partial SABR. 1 patient with 14 lesions irradiated received proton therapy. All the surviving patients are continuing using targeted therapy while 81% patients complete at least 1-year PD-1 therapy. 10 patients (20%) had grade 3 drug-related AEs: pneumonitis (n = 2), elevated alanine transaminase (n = 4), myositis (n = 1), hand-foot syndrome myositis (n = 1), enteritis (n = 1), fatigue (n = 1). There were 1 grade 4 AEs of upper gastrointestinal bleeding. No grade 3-5 RT-related AEs was found. ORR and DCR for irradiated lesion were 51% and 98%. Median OS and PFS2 was not reached. Median PFS1 was 14(6-22) months. Estimated 1- and 2-yr OS, PFS1 and PFS2 were 90% and 90%, 56% and 38%, 74% and 51% respectively. Univariate analysis showed that an PFS1 benefit was found in patients who received radiation before systemic therapy failure (p = 0.038).We investigated the high-dose RT in combination of concurrent targeted and immunotherapy in patients with metastatic RCC. We found that this treatment regimen was well tolerated, with good cancer control. Early use of high-dose RT to multi-lesions may improve PFS. Partial-SABR for bulky lesions close to critical organs could be safely and effectively applied under certain circumstances. These encouraging findings warrant further investigation.