Faecal occult blood testing (FOBT) as screening for colorectal cancer: the current controversy

Effects of a probiotic soy product and physical exercise on formation of pre-neoplastic lesions in rat colons in a short-term model of carcinogenic

Purpose

In this study the influence of moderate or intense physical exercise, alone or in combination with the consumption of a soya product fermented with Enterococcus faecium, on the development of colon cancer induced chemically in rats with 1,2-dimethylhydrazine (DMH), was investigated.

Methods

Eighty male Wistar SPF rats were randomly allocated to 8 groups (n = 10). One week after the start of the program of product ingestion and/or physical activity, all animals except the controls (group I) were injected subcutaneously with 50 mg/kg b.w. of 1,2-dimethylhydrazine (DMH). This procedure was repeated at the end of the second week. At the end of the 6-week experiment, all the animals were euthanized; the colons were removed and numbers of ACF was estimated.

Results

Twenty-four days after the induction of pre-neoplastic lesions, it was evident that the formation of ACF was not significantly reduced by the ingestion of the fermented product, by intense or moderate physical activity or by a combination of these factors, in comparison with the positive control group of rats (p < 0.05). On the other hand, the performance of intense exercise, on its own, increased the number of ACF.

Conclusion

The results reported in this article show that consumption of the fermented soy product described here and the practice of physical exercise (intense or moderate) were incapable, separately or combined, of inhibiting the formation of ACF in DMH-induced rats. The intense physical exercise led to an increased number of foci in the colons of these rats and, probably, to greater susceptibility to colorectal cancer.

The public prefers fecal occult blood test over colonoscopy for colorectal cancer screening

The acceptability of colorectal cancer (CRC) screening tests to the population influences adherence. Population preferences between fecal occult blood test (FOBT) and colonoscopy for CRC screening were examined by previous test experience. The study population was a random sample of 413 members of Israel's largest Health Maintenance Organization (HMO) aged 48-68 years. In a telephone interview, an explanation was provided regarding FOBT and colonoscopy. Participants were asked which they preferred and their degree (1-6) of agreement with each of eight test characteristics. Overall Attitude Scores toward FOBT and colonoscopy were compared. Predictors of colonoscopy preference and of refusal to undergo screening were examined using a logistic regression model. FOBT was preferred as a screening test by 70.2% of the participants, colonoscopy by 9.3%, 7.4% were indecisive, and 13.1% were not interested in screening. FOBT and colonoscopy similarly scored highly as life saving (5.2 vs. 5.1, respectively), with colonoscopy scoring significantly higher as time consuming (3.8 vs. 1.3, P<0.0001), disturbing (4.6 vs. 1.8, P<0.0001), painful (4.1 vs. 1.0, P<0.0001), annoying (4.8 vs. 1.9, P<0.0001), and involving risk (3.2 vs. 1.0, P<0.0001). In a logistic multivariate analysis, preference of colonoscopy was associated with the perception of being at CRC risk [odds ratio (OR): 3.1 (95% confidence interval (CI): 1.3-7.6)], with more positive attitude scores towards this test [OR: 2.2 (95% CI: 1.6-3.0)], and with a more negative one toward FOBT [OR: 0.4 (95% CI: 0.3-0.7)]. Target population preferences for CRC screening supports a policy of FOBT screening for an average risk population and colonoscopy for high-risk individuals.

Detection of colorectal cancer by a quantitative fluorescence determination of DNA amplification in stool

DNA amplification of exfoliated cells in stool represents an inexpensive and rapid test, but has only 50% to 60% sensitivity. A new quantitative method, called fluorescence long DNA, was developed and validated in our laboratory on stool obtained from 86 patients with primary colorectal cancer and from 62 healthy individuals. It consists of the amplification of stool DNA with fluorescence primers and the quantification of the amplification using a standard curve. Results are arbitrarily expressed in nanograms. The potential of the new method compared to the conventional approach was analyzed in a subgroup of 94 individuals (56 patients and 38 healthy volunteers). In the present series, DNA amplification analysis showed a specificity of 97% and a sensitivity of only 50%. Conversely, fluorescence DNA evaluation, using the best cutoff of 25 ng, showed a sensitivity of about 76% and a specificity of 93%. Similar sensitivity was observed regardless of Dukes stage, tumor location, and size, thus also permitting the detection of early-stage tumors. The present study seems to indicate that quantitative fluorescence DNA determination in stool successfully identifies colorectal cancer patients with a sensitivity comparable, if not superior, to that of multiple gene analysis but at a lower cost and in a shorter time.

Fecal multiple molecular tests to detect colorectal cancer in stool

BACKGROUND & AIMS

Evaluation of molecular alterations in fecal DNA is a potential, noninvasive, alternative tool for the detection of colorectal cancer. We analyzed a large panel of molecular alterations involved in tumor transformation and progression to define their single diagnostic contribution in terms of sensitivity, cost, and time required to carry out the different tests.

METHODS

DNA was analyzed in stool from 38 healthy individuals and in paired stools and primary lesions from 56 patients with colorectal cancer. p53 exons 5-8, K-ras exons 1-2, four fragments of adenomatous polyposis coli (APC) exon 15, and 5 microsatellite loci were analyzed. Moreover, DNA amplification was evaluated for 4 exons of both p53 and APC.

RESULTS

K-ras (34%) and p53 (34%) mutations were the most frequent alterations in tumors, followed by microsatellite instability (13%) and APC mutations (13%). The most frequent event in stool was DNA amplification (51%), followed by alterations of K-ras (11%), p53 and microsatellite instability (6%), and APC (2%). K-ras and p53 gene mutations increased the capacity of DNA amplification to detect tumor cells by 8%.

CONCLUSIONS

K-ras and p53 gene mutations were the most frequent alterations observed in stool from patients with colorectal cancer, but DNA amplification was even more frequent, being present in more than half of patients. If these preliminary results are confirmed in a prospective study on a larger case series, this approach could be used for noninvasive colon cancer diagnosis in screening programs.

Epidemiology of colorectal cancer

Colorectal cancer is a important public health problem: there are nearly one million new cases of colorectal cancer diagnosed world-wide each year and half a million deaths. Recent reports show that, in the US, it was the most frequent form of cancer among persons aged 75 years and older. Given that the majority of cancers occur in elder people and with the ageing of the population in mind, this observation gives further impetus to investigating prevention and treatment strategies among this subgroup of the population. Screening research, recommendations and implementation is an obvious priority. While there are many questions to be resolved, it is apparent that many facets of colorectal cancer are becoming increasingly understood and prospects for prevention are becoming apparent. Achieving colorectal cancer control is the immediate challenge.