THOUSAND OAKS, Calif. (AP) — Amgen Inc. reported full results Thursday on a study of its drug Vectibix as a primary treatment for colon cancer, saying the drug extended survival compared to chemotherapy alone. Amgen said patients treated with Vectibix and chemotherapy lived for a median period of 9.6 months before the disease began to progress again. That compares with 8 months for patients who received only chemotherapy. That measurement, which is called progression-free survival, was the primary goal of the study. Patients on Vectibix were more likely to have their tumors shrink, Amgen said. Currently the drug is only approved as a third line treatment, meaning it can be marketed to doctors for use in patients who have tried two other therapies without success. Those results come from patients with tumors that lacked a mutated gene called K-Ras. The K-Ras mutation is associated with more aggressive tumors and lower rates of survival; about 35 percent of patients have it and 65 percent do not. Patients who had the K-Ras mutation lived longer on chemotherapy alone than on Vectibix. Amgen said the chemotherapy patients lived for an average of 8.8 months until their disease began to progress again, compared with 7.3 months if they were treated with Vectibix. It said that was consistent with results from previous studies. There were 1,183 patients enrolled in the study. Amgen said in August that Vectibix met the progression-free survival goal.