A Pilot Study of Stereotactic Body Radiation Therapy Combined with Cytoreductive Nephrectomy for Metastatic Renal Cell Carcinoma

Abstract

Purpose: While stereotactic body radiotherapy (SBRT) can reduce tumor volumes in patients with metastatic renal cell carcinoma (mRCC), little is known regarding the immunomodulatory effects of high-dose radiation in the tumor microenvironment. The main objectives of this pilot study were to assess the safety and feasibility of nephrectomy following SBRT treatment of patients with mRCC and analyze the immunological impact of high-dose radiation.Experimental Design: Human RCC cell lines were irradiated and evaluated for immunomodulation. In a single-arm feasibility study, patients with mRCC were treated with 15 Gray SBRT at the primary lesion in a single fraction followed 4 weeks later by cytoreductive nephrectomy. RCC specimens were analyzed for tumor-associated antigen (TAA) expression and T-cell infiltration. The trial has reached accrual (ClinicalTrials.gov identifier: NCT01892930).Results: RCC cells treated in vitro with radiation had increased TAA expression compared with untreated tumor cells. Fourteen patients received SBRT followed by surgery, and treatment was well-tolerated. SBRT-treated tumors had increased expression of the immunomodulatory molecule calreticulin and TAA (CA9, 5T4, NY-ESO-1, and MUC-1). Ki67+ -proliferating CD8+ T cells and FOXP3+ cells were increased in SBRT-treated patient specimens in tumors and at the tumor-stromal interface compared with archived patient specimens.Conclusions: It is feasible to perform nephrectomy following SBRT with acceptable toxicity. Following SBRT, patient RCC tumors have increased expression of calreticulin, TAA, as well as a higher percentage of proliferating T cells compared with archived RCC tumors. Collectively, these studies provide evidence of immunomodulation following SBRT in mRCC. Clin Cancer Res; 23(17); 5055-65. ©2017 AACR.

Conflict of interest statement

Conflict of interest statement: The authors of this manuscript report no relationship to disclose.

©2017 American Association for Cancer Research.

Figures

Figure 1. Radiation increases expression of tumor-associated antigens and immune recognition by antigen-specific T cells

A498 cells were treated or untreated with radiation. Immunomodulatory markers (A) and tumor-associated antigens (B) were measured at indicated times by flow cytometry. Data (mean ± s.e.m.) are from ≥ 3 independent experiments. (C) 96 h after treatment, A498 tumor cells were cocultured with expanded NY-ESO-1 specific CD8 T cells and monitored for IFN-ɣ secretion by ELISPOT assays. One representative experiment out of two is shown (mean ± s.e.m.). *P < 0.05 vs. 0 Gy; unpaired two-tailed Student’s t-test.

Figure 2. Tumors resected from clear cell RCC patients treated with SBRT have increased levels of calreticulin

Control (archived nephrectomy) or SBRT (radiation plus nephrectomy) RCC patient tumors were evaluated for calreticulin (A), CD80 (B), and HSP70 (C) by flow cytometry. Single parameter flow histograms of representative samples are shown (left, MFI and percentage positive is indicative of sample shown). Line indicates portion of sample that is positive for marker. Percent positive (middle) and MFI (right) values are shown wherein horizontal lines indicate mean. n ≥ 12 per condition. **P < 0.01; NS, not significant; unpaired two-tailed Student’s t-test.

Figure 3. Tumors resected from clear cell RCC patients treated with SBRT have increased levels of tumor-associated antigens

Control (archived nephrectomy) or SBRT (radiation plus nephrectomy) RCC patient tumors were evaluated for CA9 (A), MUC-1 (B), 5T4 (C), and intracellular NY-ESO-1 (D) by flow cytometry. Single parameter flow histograms of representative samples are shown (left, MFI and percentage positive is indicative of sample shown). Line indicates portion of sample that is positive for the marker. Percent positive (middle) and MFI (right) values are shown wherein horizontal lines indicate mean. n ≥ 11 per condition. *P < 0.05, **P < 0.01; unpaired two-tailed Student’s t-test.

Figure 4. Tumors resected from SBRT-treated clear cell RCC patients have higher density of proliferating CD8+ T cells and FOXP3+ cells

(A) IHC of CD8+ T cells (red) and Ki67+ (brown) in either control archival samples (left) or SBRT-treated (right) resected patient RCC tumors. Scale bars: 100 μm. Total CD8+ T cells numbers and Ki67+ CD8+ T cells were quantified by Aperio image analysis software (B). FOXP3+ cell density was evaluated in control and SBRT samples (C). n ≥ 7 patient samples per condition. *P < 0.05; NS, not significant; unpaired two-tailed Student’s t-test. Horizontal lines denote mean.