Adjuvant Therapy For Colon Cancer

다국어 초록 (Multilingual Abstract)

Approximately 75% of all patients with colorectal carcinoma present at a stage when all gross carcinoma can be surgically resected. Despite that high resectability rate, approximately 50% of all colorectal adcnocarcinoma patients die of subsequent metastatic disease not apparent at surgery. Although there is interest currently in the evaluation of molecular markets such as ploidy and tumor suppressor gene mutation or deletion as prognostic markers, the most important prognostic information is still pathologic staging. Patients with stages Ⅱ and Ⅲ have a significantly in creased risk of relapse after surgical resection alone (Table 1). Because of the high risk of relapse after surgery alone, many adjuvant chemotherapy trials have been performed in colon cancer over the last 30 years. The predominant single agent used as adjuvant therapy in colon cancer has been 5-fluorouracil(5-FU). In 1988, a meta-analysis of 5-FU as adjuvant therapy in colorectal cancer showed that 5-year survival benefits ranged from 2.3% to 5.7%, but these survival advantages were not statistically significant. Even though early results were disappointing, 5-FU has continued to serve as the drug upon which many adjuvant therapy programs have been built. Three pahse Ⅲ evaluations of 5-FU plus methyl-1-(2-chloroethyl)-3-cyclohexyl-1-nitrosoruea(methyl-CCNU) versus surgery alone were completed in the 1980s. All these trials which were conducted by VASOG(Veterans Administration Surgical Oncology Group), GITSG(Gas-trointestinal Tumor Study Group) showed no benefit for methyl-CCNU plus 5-FU. The National Surgical Adjuvant Breast and Bowel Project (NSABP) performed a study (CO-1) involving 1,166 patients randomly allocated to bacillus Calmette-Guerin (BCG) or 5-FU and methyl-CCNU and vincristine (MOF) versus surgery alone. There was a statistically significant superiority in disease-free survival (p=0.02). This was the first prospective, randomized clinical trail to demonstrate a survival benefit for chemotherapy. Further analysis of the CO-1 study has demonstrated a weaking of the disease-free and overall survival benefits originally noted for MOF. Also, the general applicability of an adjuvant program based on chloroethyl nitrosourea is severely limited by the well-demonstrated incidence of treatment-induced myelodysplasia or acute leukemia occurring after methyl-CCNU therapy.