Screening strategies for colorectal cancer

Transanal endoscopic microsurgery in early rectal cancer: time for a trial?

OBJECTIVE

The optimal aim of oncological surgery is to balance cancer outcomes with preservation of function and quality of life. Radical resection (RR) offers the best curative procedure in colorectal cancer but at significant morbidity. Transanal endoscopic microsurgery (TEM) offers an alternative with less morbidity and better function. Its role remains unclear and needs to be established in the light of new emerging trends in rectal cancer. This review aims to evaluate the use of TEM and its limitations.

METHOD

PubMed and MEDLINE search was performed.

RESULTS

Strongest level of evidence (Level II) favoured TEM over RR and laparoscopic resection in term of mortality and morbidity. There was no difference in recurrence at follow-up of 41 and 56 months but neither study was adequately powered to detect a difference in recurrence/survival. Three retrospective case comparisons (Level III) also favoured TEM over RR but were subject to selection bias. Twenty eight published case series (Level IV) reported varying results due to different cancer stages, study population, full excision, adjuvant therapy and treatment indication. The oncological outcomes in TEM are similar to RR in highly selected cases but with far less mortality (near 0%), morbidity, blood loss, hospital stay and genitourinary/gastrointestinal dysfunction. TEM alone (+/- adjuvant therapy) appears sufficient for 'favourable' T1 tumours. 'Unfavourable' T1 or T2 tumours require adjuvant treatment. TEM should only be used for palliation in T3+ cancers. Seven functional studies reported significant transient dysfunction following TEM with full clinical recovery within a year. TEM is cost-effective providing sufficient cases are performed.

CONCLUSION

Significant heterogeneity limits conclusions from current literature. A trial is required. Alternate end-points to local recurrence may be required in assessing the optimal surgical approach, which balances disease control with quality of life, and probability of noncancer related death.

Detection of colorectal neoplasia with peanut-agglutinin (PNA)-reactive carbohydrate structures in rectal mucus

In contrast to normal colorectal mucosa, peanut-agglutinin-(PNA)-reactive glycoconjugates are commonly expressed in most colorectal carcinomas and in some pre-malignant conditions such as adenomas and ulcerative colitis. Since enzymatically detectable galactose-beta1-3-N-acetyl-galactosamine residues are found in rectal mucus obtained from patients with carcinoma of the large bowel, it was investigated here whether PNA-reactive carbohydrate structures in rectal mucus can be exploited in the detection of colorectal neoplasia. Samples of rectal mucus obtained from 261 randomly selected patients with colorectal symptoms were applied on nitrocellulose filters. The presence of PNA-reactive glycoconjugates in mucus samples was determined by a peroxidase-conjugated PNA-overlay procedure. The results were correlated to findings from total colonoscopy/surgery and histopathology. PNA-reactive carbohydrate structures were detected in 76% of patients with carcinoma (p < 0.005), in 62% of patients with adenoma (p < 0.005), in 69% of patients with inflammatory bowel disease (p < 0.005), and in 38% of patients with hyperplastic polyps (NS), in contrast to 21% of the control subjects with macroscopically normal colorectal mucosa. These results show that PNA-reactive carbohydrate alterations in rectal mucus correlates with neoplastic and hyperproliferative conditions of the colorectal mucosa. The specificity of the PNA test for colorectal neoplasia was 76%. Therefore the use of more discriminate carbohydrate probes are needed for the pre-symptomatic detection of colorectal neoplasia.

Results of a pilot study of endoscopic screening of first degree relatives of colorectal cancer patients in Italy

STUDY OBJECTIVE

Screening recommendations for colorectal cancer include sigmoidoscopy in asymptomatic, average risk persons aged 50 and over and colonoscopy every three to five years in high risk groups. Little is known about the eligible population's compliance with endoscopic screening. This is the first Italian report of an endoscopic screening programme for colorectal cancer patients' relatives.

DESIGN

In 1986, a pilot project for colorectal cancer screening by endoscopy in high risk subjects was started in the Desio (Milan, Italy) public health service region. The results obtained after seven years are described.

SETTING

The names of 536 inhabitants with colorectal cancer diagnosed between January 1975 and December 1984 and their relatives' addresses were obtained from the Regione Lombardia Health System records and from the municipal registry offices respectively.

PARTICIPANTS

From October 1986 to October 1993, 778 first degree relatives aged 20-75 were offered colonoscopy.

MAIN RESULTS

After seven years, 233 (29.9%) had undergone endoscopic examination, mostly up to the splenic flexure. Being > 60 in age at the start of the programme negatively affected the participation (p < 0.05). Two cancers were detected and adenomatous polyps were found in another 24 of those screened (frequencies 0.9% and 10.3% respectively). Male gender (p < 0.05), increasing age in males (p < 0.01), and two or more affected relatives in females (p < 0.01) positively affected the frequency of polyps detection.

CONCLUSION

These results suggest that about 30% of the eligible population would comply at least with sigmoidoscopic screening. The collaboration of family doctors and more widespread public information about the ability to cure colorectal cancer are necessary for better compliance.

Colorectal cancer screening

The decision whether to launch a screening program in asymptomatic patients of average risk for colorectal cancer and the selection of the appropriate protocol for screening are complex issues. There are still many unanswered questions. Many organizations such as the American Cancer Society, the World Health Organization Collaborating Center for the Prevention of Colorectal Cancer, and the U.S. National Cancer Institute advocate screening with annual Hemoccult tests and screening with flexible sigmoidoscopy every 3 to 5 years in patients more than 50 years of age. The U.S. Preventive Services Task Force, the Canadian Task Force on Periodic Health Examination, and the International Union Against Cancer have not recommended screening asymptomatic average-risk patients for colorectal cancer. One study showed a small but significant benefit (3 per 1000) of the rehydrated annual Hemoccult test in reducing mortality from colorectal cancer. To embark on a mass screening strategy as recommended, however, would require significant costs, increases in physician training, improved access to the requisite technology, and enhancements in patient and physician compliance. Furthermore, the high false-positive rates of the rehydrated Hemoccult tests would lead to many unnecessary tests, causing greater expense as well as patient discomfort and anxiety. It is, therefore, premature to recommend mass screening for colorectal cancer in asymptomatic individuals at this time. Further research is needed to identify risk factors (such as genetic markers) better and to develop and evaluate screening strategies targeted at those with high risk for colorectal cancer. In the meantime, efforts at primary prevention for the general population should be increased (through nutrition and exercise). Patients over the age of 50 who desire screening should be given information of the benefits and risks of screening and together with their physicians decide on a screening strategy that suits their needs and values.