Should we be screening for colorectal cancer?

Mass population screening for asymptomatic neoplastic disease is now national policy in the UK for breast cancer and has been established for many years in the early diagnosis of carcinoma of the cervix. Cancer screening is based on the concept that treatment is more effective when the disease is localised and aims to detect it when it is at a less advanced clinico-pathological stage prior to the development of symptoms. Because colorectal cancer develops in benign adenomatous polyps which are often amenable to endoscopic resection, screening may both reduce the incidence of the disease as well as improving outcome from it. Flexible sigmoidoscopy screening focuses mainly on the detection of potentially malignant adenomas, their endoscopic removal producing a decrease in colorectal cancer incidence. It is a promising approach but conclusive data on effectiveness from a Medical Research Council-sponsored multicentre randomised controlled trial will not be available before 2006. Faecal occult blood testing aims to preferentially detect early stage invasive disease. Three randomised controlled trials of faecal occult blood screening show that the disease can be detected earlier in its development leading to reduced mortality from the disease--and that this is achieved at reasonable cost. The Department of Health is currently giving consideration to its national implementation.     

基于GEO结直肠癌芯片数据的生物信息学分析

目的 利用生物信息学分析方法,挖掘结直肠癌(CRC)的关键基因并探索其发病机制.方法 在公共基因芯片数据库(GEO)中下载结直肠癌表达谱芯片数据,在GCBI实验室中筛选出结直肠癌显著差异的基因,分别对显著差异基因作GO富集分析、KEGG通路分析、蛋白质相互作用(PPI)网络分析.进一步利用cytoscape将PPI结果建立互作模块.结果 通过差异分析得出在正常结直肠组织、结直肠腺瘤、结直肠癌中表达量逐步明显下调的基因有492个,逐步明显上调的有248个,共有740个显著差异基因.GO富集分析主要体现在各种代谢过程、细胞增殖、信号调节、RNA聚合酶Ⅱ转录因子活性等.KEGG信号通路主要富集在癌症转录失调、细胞周期及p53信号通路等.并利用互作模型筛选出CDK1、MCM2、CDC6、CCNA1、CCNB2、CDKN1B、ORC1、E2F1、CHEK1、PCNA等45个与结直肠癌发生发展关系密切的关键基因.关键基因主要富集在细胞周期、病毒致癌机理、癌症相关、p53及PI3K-Akt等信号通路.结论 通过生物信息学对基因芯片数据的分析,能获取结直肠癌的关键基因及其相关通路,为后续研究提供依据.     

Cost-effectiveness analysis on screening for colorectal neoplasm and management of colorectal cancer in Asia

Background  Faecal occult blood testing (FOBT), flexible sigmoidoscopy (FS) and colonoscopy are recommended for subjects above 50 years of age for screening for colorectal cancer (CRC).
Aim  To evaluate the cost-effectiveness of FOBT, FS and colonoscopy on the basis of disease prevalence, compliance rate and cost of screening procedures in Asian countries.
Methods  A hypothetical population of 100 000 persons aged 50 undergoes either FOBT annually, FS every 5 years or colonoscopy every 10 years until the age of 80 years. Patients with positive FOBT or polyp in FS are offered colonoscopy. Surveillance colonoscopy is repeated every 3 years. The treatment cost of CRC, including surgery and chemotherapy, was evaluated. A Markov model was used to compare the cost-effectiveness of different screening strategies.
Results  Assuming a compliance rate of 90%, colonoscopy, FS and FOBT can reduce CRC incidence by 54.1%, 37.1% and 29.3% respectively. The incremental cost-effectiveness ratio (ICER) for FOBT (US$6222 per life-year saved) is lower than FS (US$8044 per life-year saved) and colonoscopy (US$7211 per life-year saved). When the compliance rate drops to 50% and 30%, FOBT still has the lowest ICER.
Conclusion  FOBT is cost-effective compared to FS or colonoscopy for CRC screening in average-risk individuals aged from 50 to 80 years.     

Review article: genetic testing and counselling for hereditary colorectal cancer

Colorectal cancer is the second leading cause of cancer death, after lung cancer, in the USA. The great majority (80%) of patients with colorectal cancer have sporadic disease with no evidence of having inherited the disorder. In the remaining 20%, a potentially definable genetic component exists. With the discovery of gene mutations related to hereditary colorectal cancer, risk assessment based on genetic test results is now feasible. The following review focuses on the two well-described colorectal cancer genetic syndromes-familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, the process of genetic counselling, currently available genetic tests, and indications for their use.