The impact of primary tumor location in patients with metastatic colorectal cancer: a Korean Cancer Study Group CO12-04 study oleh Jae Ho Byun, Joong Bae Ahn, Sun Young Kim, Jung Hun Kang, Dae Young Zang, Seok Yun Kang, Myoung Joo Kang, Byoung Yong Shim, Sun Kyung Baek, Bong-Seog Kim, Kyung Hee Lee, Soon Il Lee, Sang-Hee Cho, Byeong Seok Sohn, Samyong Kim, In Gyu Hwang, Eun Mi Nam, Bong-Gun Seo, Sang Cheul Oh, Myung-Ah Lee, Sang-Cheol Lee, Ji Hyung Hong, Young Suk Park