Simplify the following text for a Grade 12 native English-speaking person.
Original: Metastatic renal cell carcinoma presents a special challenge to oncologists , as about 70 % of patients with renal cell carcinoma develop metastases during the course of their disease , and 5 year survival for patients with metastatic renal cell carcinoma is between 5-15 % , though it is much improved if metastatectomy and nephrectomy to remove all visible disease is performed .
Simplified: Oncophage cancer vaccine may also be effective in the treatment of renal cell carcinoma . Surgery to remove liver metastases in patients with metastatic renal cell carcinoma involving the liver may be beneficial .