An analysis of the age distribution of colon cancer in adenomatosis coli

Prevention of colorectal cancer: How many tools do we have in our basket?

Prevention is the main strategy in order to reduce colorectal cancer incidence and mortality. It can be accomplished through primary prevention, using measures affecting factors known to confer higher risk of colorectal cancer, or through secondary prevention, aimed at early diagnosis of cancer or preneoplastic lesions in groups of subjects at increased risk of cancer. Although primary prevention should be the goal for future years, because it acts on the probable causes of colorectal cancer, at present it seems that secondary prevention is more effective on colorectal cancer survival, and the approaches which have yielded the most satisfying results, in terms of reduced mortality for cancer, are those aimed at detecting preneoplastic lesions, or cancer at an early stage in selected groups of subjects at average or increased risk of colorectal cancer. These groups are subjects aged 50years or older, affected individuals (gene carriers) or family members of hereditary colorectal cancer syndromes (i.e., Lynch syndrome and familial adenomatous polyposis), and patients with inflammatory bowel diseases. The most effective procedures used, though with some drawbacks, are fecal occult blood tests and colonoscopy. Future research should be addressed to find new approaches that will render preventive strategies more acceptable for the population, and more cost-effective.

Colorectal cancer--time as the most important carcinogen: a risky hypothesis about risk

The likelihood of having cancer increases proportionally with a constant power of age, beginning at 25 years old. An equation has been proposed that reproduces this incidence-age relationship, but until now the explanation remains unknown. In this paper, a hypothesis is presented in which tumoral development in human colon and rectum would be the consequence of having exceeded the 'limit number' of mitoses that every stem cell undertakes, from its origin until exhausting the security mechanisms that control the correct replication of genome. The age of cancer appearance would depend on the epithelial turnover time which basically responds to a genetic control.

Clinical and biologic features of adenomatosis coli in Northern Italy

BACKGROUND

Familial adenomatous polyposis (FAP) is a hereditary disease characterized by more than 100 adenomas scattered in the large bowel and by various extracolonic manifestations. We proposed a) to establish the frequency of the disorder in Northern Italy, b) to describe the most relevant clinical findings, and c) in a subgroup of 21 patients (from 8 families), to evaluate the spectrum of mutations of the APC gene.

METHODS AND RESULTS

Patients with FAP diagnosed between 1961 and 1991 were referred to our Study Group from surgery and gastroenterology units of the region Emilia-Romagna. The incidence of FAP was in the order of 1 in 16,500, with about a third of patients being 'single' cases. Colorectal malignancies were present in 75.6% of symptomatic patients but absent in most (93.75%) of the asymptomatic family members ('call-up' individuals). Gastric, duodenal, and jejunal adenomas were found in 8.2%, 30.6% and 53.3% of the investigated patients, respectively. Congenital hypertrophy of the retinal pigment epithelium and occult jaw lesions were seen in 64.7% and 39.5% of FAP patients but only in 0.5% and 2.5% of a matched, by age and sex, control population. These two clinical markers had a specificity of 99% and 97%, although their sensitivity was 64% and 39%. Finally, mutations of the APC gene were detected in 6 families (16 affected individuals) of the 8 families (21 affected individuals) tested; no correlation could be found between genotype and phenotype.

CONCLUSIONS

This study confirms that early diagnosis is essential for an appropriate management of FAP patients, although this aim remains elusive in single cases. High-risk individuals are ideal candidates for APC gene mutation analysis, which should be offered to all first-degree relatives of affected patients.

Sartwell's incubation period model revisited in the light of dynamic modeling

The objective is to look into the well-known robustness of Sartwell's disease incubation period (IP) lognormal model. A new approach is proposed that embeds the pathogenesis of infection into the framework of percolation theory derived from the physical sciences. A two-step model of the individual disease process is proposed. The first step has a stochastic basis: it is aimed at establishing the threshold position of subjects bound to be diseased. Agent and host factors entertain and help the process reach the threshold. They include all the biologic risk factors (age, exposure dose and intensity, route of inoculation, etc.) to which Sartwell's model is usually found robust. The threshold is the point of no return of the disease process. The threshold provides the initial conditions of the second step. The second step traces the evolution of the pathologic process until disease onset: it is based on a nonlinear deterministic model that progressively unfolds the individual fates. As a chaotic regime is embedded into the model and as chaos unavoidably develops at some time entailing disease onset, the IP distribution becomes independent of the initial conditions laid out at the threshold. Unpredictable disease time courses and onsets are obtained. Biological examples supporting the model are provided. A simulation of 1000 pathologic processes is undertaken according to a simple birth-and-death process of microorganisms or cancer cells. As expected, a lognormal fits the IP distribution over a wide range. A lack of lengthy IPs is, however, observed. A simple multiplicative process coincides exactly with a lognormal model, but a multiplicative-competitive process such as that which is embedded in the nonlinear deterministic model has a narrower distribution. Large sample sizes are, however, needed to uncover this departure from the lognormal. Biologically, at least two phases of the empiric IP should be told apart: lengthy IPs should be distinguished from short and median IPs. Lengthy IPs emphasize interaction (complexity) between the disease progression and the immunological defenses of the host. Simulated distributions involving process complexity closely fit selected cancer data sets. Process complexity of the host pathologic unfolding can actually be recognized and quantified.

Familial adenomatous polyposis: mutation at codon 1309 and early onset of colon cancer

The clinical course of familial adenomatous polyposis (FAP) varies considerably between patients. Prediction of the severity of the disease is important in the interest of effective cancer prevention. We examined whether age at diagnosis of FAP due to gastrointestinal symptoms and age at death due to colorectal cancer are related to the site of mutation in the responsible gene. 225 families with FAP were screened for mutations. The deletion of 5 base pairs at codon 1309 within exon 15 (known to be the most common mutation) was identified in 20 families; other mutations within exons 7-15 were found in 49 families. In patients with the 5 base-pair deletion at codon 1309, gastrointestinal symptoms and death from colorectal cancer occurred about 10 years earlier than in patients with other mutations. The 1309 mutation leads to development of colonic polyps at a younger age, thus giving rise to an earlier malignant transformation. This relationship should be taken into account in strategies for preventing cancer in patients with FAP.

Correlation between relatives for colorectal cancer mortality in familial adenomatous polyposis

It has long been realized that age-specific cancer mortality in Familial Adenomatous Polyposis (FAP) was bimodal, and a theory was proposed in which the involved locus was polymorphic in the general population. After the molecular cloning of the region 5q21, it has been suggested that the phenotypic variability in FAP may be due to the interaction of two loci, one of which is polymorphic. We show that these two hypotheses lead to different predictions of the correlation between relatives for a phenotypic trait, and use colorectal cancer mortality data from the Italian Polyposes Registry to verify them. We conclude that the first of the two is more likely and suggest that the same variation that we observe among the affected subjects is present in the general population, thus causing a significant difference between individuals for colon cancer susceptibility.

The impact of familial adenomatous polyposis on the tumorigenesis and mortality at the several organs. Its rational treatment

The authors reviewed the case records of 1050 familial adenomatous polyposis (FAP) patients who were registered at their institution. The organ-specific morbidity and mortality rates of malignant tumor in FAP patients were compared with those of the general population of Japan, and the prognosis after rectum-preserving operation also was calculated. The cumulative prevalence of colorectal carcinoma at the age of 44 years was 0.52 for men and 0.61 for women. The observed/expected morbidity ratio was 20.9 (95% confidence interval, 10.8-36.6) for thyroid carcinoma, 3.08 (2.03-7.75) for gastric carcinoma, and 295 (263-330) for colorectal carcinoma. The observed/expected mortality ratios was 250 (112-447) for periampullary and small intestinal carcinoma, 3.43 (1.77-6.0) for gastric carcinoma, and 210 (183-241) for colorectal carcinoma. The risk of rectal carcinoma after ileorectal anastomosis was 13% (8.5-17.5%) at 10 years and 37% at 20 years. The results clarified the impact of FAP on the carcinogenesis in several organs as a whole including preserved rectum, and suggested a direction of the rational treatment of FAP.

Childhood brain tumor: presentation at younger age is associated with a family tumor history

In a registry-based sample of 361 children with a brain tumor, those whose grandparents and great-grandparents had a history of any kind of tumor were younger at the time of presentation than were those who lacked this family history (p = 0.1). In post hoc analyses, the age difference was most apparent among children with cerebral tumors, and when family history was limited to brain tumors and to great-grandparents. These findings are in keeping with the hypothesis that a familial tumor diathesis contributes to an early age at onset of a brain tumor in some children.

Impact of a hospital-based register on the management of familial adenomatous polyposis

Colorectal cancer in familial adenomatous polyposis is a preventable disease in at-risk relatives of patients with primary cases. Until the recent establishment of a register in Western Australia, there has been no registration of pedigrees or central organization of surveillance in Australia. In the present study, the experience of 20 such families who were associated with The Royal Melbourne Hospital was documented, with an analysis of the reasons for any failure of management. The impact of a hospital-based register on the management of the disease was studied. In each family, results were categorized according to whether "at-risk" relatives had been diagnosed at surveillance examinations, and whether the Hospital register were involved. Before involvement with the register, 24 family members presented with symptomatic polyposis after the first affected case had been diagnosed. Eighteen of these had colorectal cancer at diagnosis, and 16 subjects now are dead. Identifiable reasons for the failure of surveillance were family communication failure (two cases), family denial (two cases), failure of the hospital clinic (two cases) and a failure to cover extended branches of families who were living locally (nine cases), interstate (four cases) or overseas (three cases). In contrast, only two (6%) of 33 affected cases that were identified at a planned surveillance endoscopy had colorectal cancer at diagnosis. Without the active surveillance of at-risk family members, lethal delays in diagnosis are likely to occur. Most reasons for failure potentially are correctable by a dedicated registry that is responsible for notifying clinicians and patients about the timing of surveillance procedures.

The multihit model of carcinogenesis: etiologic implications for colon cancer

A new multihit model of carcinogenesis is developed for use in evaluating age-specific cancer incidence rates in human populations. The model allows for some heterogeneity in both risk (perhaps genetic) and pathway (number of hits). Fitting the model yields estimates of (1) levels of effect of background exposure to environmental agents, (2) tumor growth times after initiation of a malignant cell, and (3) relative sizes of high-risk groups in a human population. Maximum likelihood procedures are used to fit the model to the polyposis coli data of Veale and the colon cancer incidence data from the Third National Cancer Survey. Model estimates may be verified in some cases by review of independent data in the literature and results have both theoretical and practical implications. Findings are generally consistent with the adenoma-carcinoma etiologic sequence postulated by Hill, Morson and Bussey with one exception. A large proportion of the population may be at risk of four-hit colon tumors following a non-adenoma etiologic sequence.

Multistage risk models and the age pattern in familial polyposis coli

Multistage risk models provide a close fit to most age patterns of adult-onset cancers. Such models posit that a number of events must occur before some cell in a tissue is transformed from normal to neoplastic. When an approximate version of the models has been fitted to data, this number has been estimated to be about 4-6. In fitting the same approximate model to the age pattern of onset of colon cancer in bearers of the Familial Polyposis coli (FPC) gene, several authors have found that the number of stages estimated was about two to three fewer than those for colon cancer in the general population. However, when an exact multistage model is used rather than an approximation to it, this is no longer the case: the number of stages estimated from the general population becomes too large to be compatible with what is known about carcinogenesis from laboratory experiments, and the number estimated from FPC victims is larger than that for the general population. "Inherited-hit" models of the nature of the FPC gene may be correct at the cellular level, but multistage models as commonly formulated cannot be used on data on the age-onset patterns in populations of individuals to infer such mechanisms or estimate their parameters.