Hi Mary, went to UNC for 2nd opinion. (Husband, Charlie, 52, CC diag. 6/07). They told us that Charlie's tumors are too large for Cyberknife. Usually is used on very small tumors. (His entire left lobe is tumor and a few in his right lobe). I don't know if this helps at all, but it may give some idea on size of tumors for this procedure. Good luck and God Bless!