Colon cancer screening

Colonoscopic surveillance for family history of colorectal cancer: are NHMRC guidelines being followed?

OBJECTIVES

To assess whether referrals for surveillance colonoscopy and subsequent follow-up recommendations for patients with a family history of colorectal cancer concurred with the published National Health and Medical Research Council (NHMRC) guidelines.

DESIGN

A prospective audit of patients with a family history of colorectal cancer referred for surveillance colonoscopy. Follow-up recommendations were assessed retrospectively.

SETTING AND SUBJECTS

All patients referred to a major teaching hospital for surveillance colonoscopy on the basis of a family history of colorectal cancer from 2 January 2000-15 April 2001.

MAIN OUTCOME MEASURES

Concurrence of referrals and recommendations with NHMRC guidelines.

RESULTS

Of 340 patients referred because of a family history of colorectal cancer, 202 (83 men, 119 women) were asymptomatic. Their mean age was 50 years (95% CI, 48.3-51.6 years). The family history of 95 (47%) of these patients satisfied the NHMRC criteria for colonoscopic surveillance. Another 20 patients (17%) satisfied the criteria, but were referred before the recommended age to commence surveillance. Analysis by referral source showed that the proportion of referrals meeting NHMRC guidelines was higher from specialists than from general practitioners (75% v 45%), and this difference was significant. Follow-up recommendations, when made, concurred with NHMRC guidelines in 81% of cases.

CONCLUSIONS

Further education of the medical community is required to increase understanding of colorectal screening strategies and ensure appropriate resource allocation.

Colonic cancer and polyps

Colorectal cancer (CRC) is one of the best studied cancers. It is easily accessible and develops slowly over several years from premalignant lesions (adenomatous polyps) to invasive cancers. The key molecular events in this sequence have been characterized. Different screening strategies have proven to be effective in lowering both the mortality and the incidence of CRC. Nevertheless, CRC is still the second leading cause of cancer-related deaths for both men and women in the USA and other Western countries. An estimated 130 000 new cases and more than 50 000 deaths have been diagnosed in the USA in 2000. Surgical resection remains the only curative treatment, and the likelihood of cure is greater when the disease is detected at an early stage. Hereditary non-polyposis colorectal cancer (HNPCC) and the different polyposis syndromes such as familial adenomatous polyposis (FAP) or Peutz-Jeghers disease are rare causes of CRC but have been a major focus of research in past years, helping with the understanding of the molecular events in carcinogenesis. This review summarizes our current knowledge of the pathogenesis and management of colorectal polyps and polyposis syndromes as well as sporadic CRC.

Barriers to screening for colorectal cancer

Rapidly growing interest in colon cancer screening is a crucial first step to identifying and reducing many of the barriers that impede population screening for this common disease. Promoting screening demands health care policy change to increase the percentage of Americans with insurance coverage that includes a colon cancer screening benefit. A systematic approach to screening with invitations that come from a clinician are likely to be the most effective way to prompt more individuals to be screened. Awareness campaigns and patient educational aids, including decision tools, implemented in multiple sites, such as worksites, community centers, health care systems, and physician offices, increase the percent of eligible Americans who understand their personal risk, the need for screening, and the options available to them.

Germline characterization of early-aged onset of hereditary non-polyposis colorectal cancer

OBJECTIVES

Hereditary non-polyposis colorectal cancer (HNPCC) is characterized by the early onset of colorectal cancer (approximately 40 years). Adolescent colorectal cancer is unusual in HNPCC families. We speculated that some DNA mismatch repair germline mutations might be associated with early onset of disease.

STUDY DESIGN

Genomic DNA was extracted from members of a kindred with virulent HNPCC fitting the Amsterdam Criteria for HNPCC and sequenced for 2 DNA mismatch repair genes, hMSH2 and hMLH1. A sigmoid adenocarcinoma from the 14-year-old proband was analyzed for highfrequency microsatellite instability and immunostained for DNA mismatch repair gene expression.

RESULTS

A germline mutation was identified at nucleotide 676 (codon 226) of the hMLH1 gene. The C to T transition created a nonsense mutation, truncating the hMLH1 protein. This mutation also alters the splice donor sequence, because nucleotide 676 is 2 base pairs from the 3' end of the exon 8. The proband's tumor demonstrated high-frequency microsatellite instability and displayed loss of hMLH1 expression, indicating bi-allelic inactivation of hMLH1.

CONCLUSIONS

A complex mutation of hMLH1 at codon 226 is associated with adolescent onset of colorectal cancer in an HNPCC family. Genetic screening of other suspected HNPCC families with unusually young members with cancer might reveal certain genotypes with particularly virulent forms of this disease.

A molecular rationale for the how, when and why of colorectal cancer screening

Colorectal cancer remains a leading cause of cancer-related mortality in the United States. Recently, colorectal cancer screening and colorectal cancer prevention have gained national attention. In response, the American Gastroenterological Association, the American College of Gastroenterology and the Agency for Healthcare Policy and Research have published recommendations for colorectal cancer screening and surveillance in patients with sporadic as well as hereditary forms of colorectal cancer. This review will focus on the basic molecular differences underlying the formation of carcinoma in patients with sporadic colorectal cancer, and the heritable syndromes of familial adenomatous polyposis (FAP), hereditary non-polyposis colorectal cancer (HNPCC), and juvenile polyposis (JPS). By appreciating the molecular mechanisms underlying these four types of polyp cancer syndromes, the differences in clinical time course for progression from polyp to carcinoma and in current screening recommendations for patients with sporadic adenomas, FAP, HNPCC and JPS can be better understood.