Purpose

To evaluate the feasibility, safety, oncologic outcomes, and immune effect of neoadjuvant stereotactic radiation (Neo-SAbR) followed by radical nephrectomy and thrombectomy (RN-IVCT).

Methods and materials

These are results from the safety lead-in portion of a single-arm phase 1 and 2 trial. Patients with kidney cancer (renal cell carcinoma [RCC]) and inferior vena cava (IVC) tumor thrombus (TT) underwent Neo-SAbR (40 Gy in 5 fractions) to the IVC-TT followed by open RN-IVCT. Absence of grade 4 to 5 adverse events (AEs) within 90 days of RN-IVCT was the primary endpoint. Exploratory studies included pathologic and immunologic alterations attributable to SAbR.

Results

Six patients were included in the final analysis. No grade 4 to 5 AEs were observed. A total of 81 AEs were reported within 90 days of surgery: 73% (59/81) were grade 1, 23% (19/81) were grade 2, and 4% (3/81) were grade 3. After a median follow-up of 24 months, all patients are alive. One patient developed de novo metastatic disease. Of 3 patients with metastasis at diagnosis, 1 had a complete and another had a partial abscopal response without the concurrent use of systemic therapy. Neo-SABR led to decreased Ki-67 and increased PD-L1 expression in the IVC-TT. Inflammatory cytokines and autoantibody titers reflecting better host immune status were observed in patients with nonprogressive disease.

Conclusions

Neo-SAbR followed by RN-IVCT for RCC IVC-TT is feasible and safe. Favorable host immune environment correlated with abscopal response to SABR and RCC relapse-free survival, though direct causal relation to SABR has yet to be established.

BACKGROUNDMetastases are the hallmark of lethal cancer, though underlying mechanisms that drive metastatic spread to specific organs remain poorly understood. Renal cell carcinoma (RCC) is known to have distinct sites of metastases, with lung, bone, liver, and lymph nodes being more common than brain, gastrointestinal tract, and endocrine glands. Previous studies have shown varying clinical behavior and prognosis associated with the site of metastatic spread; however, little is known about the molecular underpinnings that contribute to the differential outcomes observed by the site of metastasis.METHODSWe analyzed primary renal tumors and tumors derived from metastatic sites to comprehensively characterize genomic and transcriptomic features of tumor cells as well as to evaluate the tumor microenvironment at both sites.RESULTSWe included a total of 657 tumor samples (340 from the primary site [kidney] and 317 from various sites of metastasis). We show distinct genomic alterations, transcriptomic signatures, and immune and stromal tumor microenvironments across metastatic sites in a large cohort of patients with RCC.CONCLUSIONWe demonstrate significant heterogeneity among primary tumors and metastatic sites and elucidate the complex interplay between tumor cells and the extrinsic tumor microenvironment that is vital for developing effective anticancer therapies.