Improvement of long-term survival of colorectal cancer in Japanese-Americans of Hawaii from 1990 to 2001

Background: To compare the long-term survival of colorectal cancer (CRC) during two 6-year periods using patients with similar characteristics of the same ethnicity in Hawaii. Methods: A retrospective review of Japanese-American patients in Hawaii with CRC surgically resected and followed more than 5 years in a single institution. Patients were divided into two groups by date that patients had surgery: Group 1; 1990-1995, and Group 2; 1996-2001 (introduction of newer chemotherapy, aggressive surgery for liver metastases including radiofrequency thermal ablation). Results: A total of 344 patients in Group 1 (median age 69.5 years) and 330 patients in Group 2 (median age 71.7 years) were included. There were no differences between two groups in gender, age, anatomic site, carcinoembryonic antigen, tumor size, histologic grade, and TNM stage distribution, including pT, pN, and pM status. Overall 5-year survival rate difference approached significance between two groups (Group 1: 73.2% vs. Group 2: 78.9%; p = 0.097). Particularly, there was significant difference in stage IV patients (Group 1; 8.7% vs. Group 2: 26.0%; p = 0.030) and histologic grade 3 (Group 1; 41.67% vs. Group 2: 67.73%; p = 0.032). Subgroup analyses showed significant difference (p < 0.05) for more advanced cancers (larger tumor, node positive, metastatic disease, poorly differentiated cancer). Conclusions: In this study of patients with the same ethnicity, the better survival outcome in latter (Group 2) patients suggests improvement of treatment, especially for patients with more advanced and metastatic cancer (stage IV).