A 61-year-old woman underwent surgical resection of rectal cancer(SI, N3, Stage IIIb)and received 12 courses of adjuvant mFOLFOX6 chemotherapy. Six months after completion of adjuvant chemotherapy, she was found to have pulmonary metastases, and was treated with FOLFIRI plus bevacizumab. After 6 courses of chemotherapy, the pulmonary nodules showed central cavitation without any change in size. After 6 additional courses of chemotherapy, pulmonary lesions increased in and had consolidated. She was treated with regorafenib as second-line chemotherapy for recurrent disease. After 6 courses of regorafenib, the pulmonary nodules became cavitated. According to the RECIST criteria, the tumor response was stable disease. However, the morphology was significantly changed and tumor growth had been controlled for a long time. Assessment of tumor response depends not onlyon size according to the RECIST criteria, but also on the morphologic response when we assess tumor response to molecular targeted drugs.