Patient: Diagnosed with adenocarcinoma of the lung (upper lobe of the left lung) in November 2006 at a local hospital, followed by surgery and post-operative chemotherapy. small nodules in the lung were found on re-examination in September and December 2009, and on re-examination in March this year, the nodules were found to be larger, and intrapulmonary recurrence (lower lobe of the left lung) was confirmed. After 2 cycles of chemotherapy, I had a CT examination and the size of the tumor did not change much. I heard that targeted therapy is effective for lung cancer and has few side effects. Under what circumstances should targeted therapy be used? Is it only used when chemotherapy does not work?