Ablative Radioembolization of Renal Cell Carcinoma Trial

Renal cell carcinoma (RCC) is the 8th most common cancer in the United States with 81,610 new cases diagnosed each year. 70% of new RCC cases are localized, non-metastatic at initial diagnosis; however, the risk of disease recurrence or progression to metastatic disease is higher for larger tumors and those with higher grade disease. The standard therapy for localized renal cell carcinoma (RCC) is surgery - either partial or radical nephrectomy. However, a substantial proportion of patients with RCC are not good surgical candidates, as the average age at diagnosis is 64-year-old, and obesity, smoking, hypertension and renal disease known risk factors. Currently there are no established standard-of-care therapies for patients who are not eligible for surgery.

Unmet Clinical Need:

There is a need to establish a definitive, minimally-invasive therapy patients for with large, non-metastatic RCC who are not surgical candidates. For non-surgical candidates with small RCC (\< 4 cm or T1a) percutaneous ablation has been established as an effective minimally-invasive curative therapy. However, there is currently no minimally-invasive standard of care therapy for patients with larger localized RCC (\> 4 cm) who are not surgical candidates, despite these patients being at higher risk for developing metastatic disease. Percutaneous ablation can be performed in patients with tumors \> 4 cm; however, long term outcomes have not been established and those ablations carry higher risks of major bleeding complications than ablation of tumours \< 4 cm. SBRT has shown some promising progression-free survival data for localized RCC; however, the radiation resistance of RCC cells require higher treatment doses to achieve cytotoxic effect. The achievable therapeutic dose of SBRT is currently limited to 30-60 Gy, often due to required reductions in the externally delivered dose to protect the commonly adjacent radiosensitive colon and/or small bowel that routinely abut the kidney.

Selective internal radiation therapy (SIRT) or Yittrium-90 (Y-90) radioembolization is an endovascular therapy whereby beads loaded with the radioactive Yittrium-90 atom are injected through a catheter into the artery or arteries supplying the tumor to deliver the radiation dose internally. Radioactive decay of the Y-90 atom within the tumor's arterial bed, deposits radiation dose within 2.5 mm (maximum 11 mm) of the bead location. As such, the internal delivery of radiation, rather than external delivery of SBRT, allows for higher doses to be delivered to the tumour without exposing adjacent vulnerable organs to significant dose. Y-90 radioembolization has great success treating hepatocellular carcinoma (HCC) in the liver, commonly achieving tumor dose levels that are nearly ten times higher than SBRT (e.g. 300-500 Gy vs. 40-50 Gy). Furthermore, it has become a standard of care therapy for HCC with recent inclusion in the major international treatment guidelines. Y-90 tumor dosage of \>400 Gy is the typical target with one major explant study showing complete pathological necrosis of HCC tumors when this dose was achieved8.