Tumours of the colon and rectum: we discover colorectal cancer

By Cristiano Antonino On Sep 27, 2022

Colorectal carcinoma is one of the leading causes of morbidity and mortality due to neoplasia in all Western and highly developed countries

There are 678,000 new cases per year worldwide, 150,000 in Europe and 30,000 in Italy.

The crude incidence in our country is 30 – 50 new cases per year per 100,000 inhabitants; the highest rates are in central and northern Italy with a higher prevalence for rectal cancer in the male sex.

12 % of all cancer deaths in men and 16 % in women are due to malignancies in this district.

Large bowel cancer has a high incidence in Western countries, close to that of gastric cancer and lung cancer (in men), and breast cancer (in women).

The importance of constitutional and genetic factors (e.g., high frequency in some populations compared to others, very high incidence in families with individuals with familial polyposis), as well as the quality and quantity of food ingested, is well established.

A diet low in vegetable fibre may favour the onset of colorectal cancer

Fibre, in fact, resulting in an accelerated intestinal transit, decreases the contact time of the mucosa with possible carcinogens), as does a diet rich in fats (cholesterol and its derivatives: substances with carcinogenic potential); a high protein diet is also capable of altering the bacterial flora of the colon (the growth of anaerobes, capable of transforming bile salts into carcinogens, prevails over aerobes).

The most prevalent colon cancer locations (about 70%) are the sigma and rectum.

Colon carcinomas, from a biological point of view, are generally neoplasms with low malignant potential, especially at an advanced age; surgery, if performed early, therefore has curative possibilities.

Symptomatology: how to recognise colorectal carcinoma?

Colorectal carcinoma is often present for a long time before manifesting itself with clinical signs.

However, depending on the site of onset, there may be different signs with different times of appearance.

Left-sided colon carcinomas are generally recognised earlier by the finding of blood in the faeces accompanied or not by diarrhoea and/or constipation.

Right-sided carcinomas have more subtle behaviour: uncharacteristic symptoms such as asthenia, malaise, rapid weight loss and anaemia for no apparent reason may be the alarm bells.

In any case, the main and common character of such neoplasms remains the high tendency to bleed, so the sign to look for is the presence of blood in the faeces.

Secondary prevention of colorectal cancer

Colorectal neoplasms currently account for 15% of all cancers and are an important cause of mortality for both sexes: in Europe and Western countries in general it is the second leading cause of cancer death both in men, after lung neoplasms, and in women, after breast neoplasms.

In Italy, the data refer to 1994, 17,760 new cases were registered in the male sex and 18,060 in the female sex for a total of 9,731 and 9,318 deaths respectively; the probability of falling ill (per 100 subjects aged between 0 and 74 years) is 4.3 for the male sex and 2.8 for the female sex.

The overall risk of falling ill with colorectal cancer varies between the North and the South in both sexes and is probably related to different eating habits and/or lifestyles; in fact, incidence and mortality are significantly higher in the North and the Centre than in the South, with differences between the extreme values close to or greater than a factor of 2.

Comparing our country’s position with regard to colorectal cancer, Italy currently ranks intermediate on the international scale with a tendency to align with the higher frequency levels typical of North America and Northern Europe.

In general, incidence is increasing while mortality is stationary with a downward trend.

Five-year survival has increased over the last 20 years (estimated percentages between 6 and 8%) with an expectation of around 60%; this positive result is due to earlier diagnosis and more effective post-surgical adjuvant treatments.

Tumours diagnosed at an early stage of disease are radically curable with surgery alone; in fact, cure rates at 5 years are proportional to the stage of disease.

The most frequent anatomical localisation, approximately 70-75%, is at the level of the sigma-rectum of which 30% can be explored manually and 60% can be detected with rectosigmidoscopy: this data is extremely useful for clinical-instrumental investigations of secondary prevention.

In view of the above, it is clear how the natural history of the disease can be influenced by prevention and early diagnosis; secondary prevention would therefore have the potential to significantly reduce disease-related mortality.

The tests available for screening colorectal neoplasms are:

Occult blood in the faeces
Rectal exploration
Rectosigmoidoscopy
Colonoscopy
Opaque cyst with double contrast medium

Recent data show that the use of screening tests increases the chance of detecting forms of colorectal cancer at an early stage, thus leading to a decrease in the mortality rate of these neoplastic diseases.

The National Cancer Institute of the U.S.A. and the American Cancer Society recommend the following rules:

Practice rectal exploration during a physical examination in asymptomatic subjects aged > 45 years;

Carry out a faecal occult blood test annually over the age of 50 and a rectosigmoidoscopy every five years.

The American Geriatric Society suggests that occult blood tests should be performed until the age of 85.

Flexible rectosigmoidoscopy is a highly sensitive test and the American Cancer Society recommends it be performed every 3-5 years.

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A single rectosigmoidoscopy towards the end of the sixth decade should identify most individuals with distal adenomas at risk of cancer.

Monitor patients at risk. Colonoscopy has a high sensitivity and specificity (>95%), but is unlikely to become a standard screening procedure in view of its high cost, low compliance and moderate morbidity; it is a test that should be performed in medium- and high-risk subjects.

The risk factors for such neoplasms are:

Environmental
Age > 50 years,
Diet high in fat and protein, low in fibre and micronutrients,
Obesity,
Smoking/alcohol
Medium-high social status

It appears that environmental factors, and in particular dietary factors, are responsible for the majority of colorectal cancers

Epidemiological studies of dietary habits and population migration have shown that diets high in animal fats and meat and low in fibre increase the risk for these cancers.

Indeed, diets high in protein and animal fats are associated with a high content of bile acids and cholesterol metabolites in the faeces of colorectal cancer patients.

In addition to high concentrations of fatty acids, calcium deficiency and the alkaline pH of stools are also mentioned; on the other hand, the protective effect of a diet rich in vegetables, fruit and cereals has been proven.

Hereditary

Familial Adenomatous Polyposis (PAF): is autosomal dominant characterised by the presence of numerous adenomatous polyps localised mainly in the Sn colon.

The polyps are not present at birth but become evident in late adolescence, exceeding the number of one thousand in several cases.

All individuals with this disease are destined to develop colorectal cancer in their lifetime.

Gardner syndrome: is similar but less frequent than PAF (1 in 14,000 births); it is characterised by the co-presence of polyps of the small intestine, desmoid tumours of the mesentery and abdominal wall, lipomas, sebaceous cysts, osteomas and fibromas; it is an autosomal dominant disease.