Colon Cancer - Diagnosis

Premise

Colon cancer, mainly represented by adenocarcinoma of the colon, is a malignant neoplasm of the large intestine which, after an early asymptomatic phase, produces numerous aspecific symptoms and signs (where "aspecific" means "common to many other diseases gut ").

Among its most notable clinical manifestations are: diarrhea, constipation, rectal bleeding, blood in the stool, anemia, abdominal pain, abdominal cramps and a feeling that the bowel is not emptying after defecation.

Colon neoplasms arise due to causes that are still unclear; however, it is certain that some factors and conditions have a decisive influence on their appearance, including: an unhealthy diet, cigarette smoking, obesity, a sedentary lifestyle, some hereditary diseases (eg: Lynch II syndrome and familial adenomatous polyposis), a certain family predisposition, the presence of intestinal polyps (or adenomatous polyps) and inflammatory bowel diseases (eg, Crohn's disease or ulcerative colitis).

Diagnosis

The diagnosis of colon cancer is often the result of a long procedure, which begins with the physical examination and the anamnesis; therefore, it continues with laboratory tests on blood and feces, followed by a digital rectal exploration; finally, it ends with several instrumental tests and a tumor biopsy.

Each step mentioned above is fundamental to the formulation of a correct and accurate diagnosis.

Only thanks to an extremely accurate diagnosis, doctors are able to plan the most appropriate treatment.

For further information: Colonoscopy and Occult Blood in Feces

Physical examination and medical history

Physical examination and anamnesis are two diagnostic evaluations that provide useful and important information regarding symptoms (eg: they lead to abdominal discomfort, changes in bowel habits, fatigue, blood on toilet paper etc. .).

Furthermore, they allow the doctor to clarify the patient's general health status and family history, and to hypothesize the possible reasons for the symptomatic situation in progress (the anamnesis, for example, provides for an extensive investigation regarding all the factors of risk associated with a certain symptom picture).

In any case, however useful and important, what emerges from the physical examination and from the anamnesis does not allow us to formulate any definitive diagnosis; this is why more in-depth research is needed, such as laboratory tests and above all instrumental tests.

Investigations that generally characterize the physical examination and the history of a suspected case of colon cancer:

• Measurement of blood pressure, heart rate and body temperature;
• Questions related to bowel habits;
• Questions related to the presence of: diarrhea, constipation, faulty shape and texture of the stool, rectal bleeding, fatigue, abdominal discomfort or pain, etc .;
• Questions intended to clarify whether there was an unexplained drop in body weight;
• Palpatory examination of the abdomen, in search of possible swellings;
• Family history questions. The intent of these questions is to clarify whether there is a familiarity or inheritance for colon neoplasms.

Laboratory tests

Also valid, but not enough for the formulation of a definitive diagnosis of colon cancer, laboratory tests generally consist of:

• Blood tests,
• Faeces analysis e
• Quantification of tumor markers .

BLOOD TESTS

Blood tests show anemia, a consequence more than recurrent in colon cancer, especially when it concerns the descending-rectum colon (80% of cases).

Furthermore, they provide information on renal (ie kidney) and hepatic (ie liver) function, whose efficiency depends directly on the general state of health of the human organism.

ANALYSIS OF FECI

Stool analysis allows us to establish its consistency and shape; furthermore, it allows the detection of blood, not visible to the naked eye.

The blood traces in the feces result from the hemorrhages inside the intestine, caused by the infiltration process of the tumor mass (in essence, it is the search for the so-called occult blood in the feces ).

QUANTIFICATION OF TUMOR MARKERS

The medical-scientific community calls tumor markers those substances found in the blood which, in the presence of a neoplasm, assume particularly high concentrations.

Tumor markers generally have a protein nature.

In colon cancer, the tumor markers that could undergo an increase in quantitative terms, thus becoming interesting from the diagnostic point of view, are three:

• the CEA (or Carcino-Embryonic Antigen ),
• the CA 15-3
• CA 19-9 (or GICA, which stands for Gastro-Intestinal Cancer Antigen ).

However, it should be pointed out that the quantification of these tumor markers is often unreliable, for several reasons including:

• A not inconsiderable number of patients have normal blood levels of CEA, which is the most important tumor marker for colon cancer.

  Therefore, a diagnostic investigation based exclusively on the quantification of this tumor marker would lead to the erroneous exclusion of colon cancer;

• In contrast to the previous case, a fair number of healthy individuals have high blood levels of CEA.

  Furthermore, studies report the rise in blood counts of CEA in 15% of non-colon cancer smokers;

• All three of the aforementioned tumor markers can assume high concentrations in the presence of neoplasms other than colon cancer. For example, CA 19-9 is typical of pancreatic cancer and can also be elevated due to stomach cancer; the CA 15-3, instead, is typically high in the presence of breast neoplasms; etc.

Digital rectal exploration

Digital rectal exploration is an "inconvenient" diagnostic test, but it has the utility of:

• Exclude or not conditions such as hemorrhoids and anal fissures, whose symptoms resemble those of colon cancer, and
• Identify any tumor mass at the level of the rectum.

Instrumental tests

The instrumental tests derive any doubt and perplexity, therefore without their recourse any definitive conclusion would be impossible.

Among the instrumental tests that allow to verify the presence of a colon tumor and study its characteristics, they are of particular importance:

• Colonoscopy,
• Flexible sigmoidoscopy,
• The enema based on barium sulfate e
• Virtual colonoscopy.

However, we must not forget the useful information that can come from:

• CT scan of the chest and abdomen . It provides information on the location and size of the neoplasm, clarifies the relationships that the tumor mass has established with the neighboring anatomical structures and detects the possible dissemination of menstruation in the regional lymph nodes, in the liver and in the lungs;
• PET . Thanks to the use of radiopharmaceuticals, it allows to identify which organs are protagonists, due to a disease against them, of metabolic and functional variations.

  Cancer cells are metabolically very active cells, therefore ideal for recognition by PET;

• Trans-rectal endoscopic ultrasound . It is a diagnostic test that combines the advantages of ultrasound (the absence of harmful radiation) with the advantages of endoscopy (observation of the organs of the human body from the inside).

  In the presence of a colon tumor, it serves to clarify the appearance of the intestinal mucosa and of the organs close to the neoplastic mass;

Colonoscopy

Colonoscopy is, in fact, endoscopy of the large intestine or large intestine; in other words, it is the diagnostic test, which allows visual exploration from within the cecum, ascending colon, transverse colon, descending colon, sigma and rectum.

From the executive point of view, the colonoscopy involves the use of a particular instrument, called a colonoscope, which the doctor gently introduces into the lumen of the large intestine, through the opening of the anus. Tubular and flexible, the colonoscope is equipped with a camera with light source which, thanks to the connection with an external monitor, allows the visualization on the latter of the internal anatomy of the intestinal portions crossed; in essence, therefore, the colonoscope is a probe, which the doctor inserts, starting from the anus, inside the second portion of intestine, to analyze its state of health.

In addition to being the first choice instrumental examination for the evaluation of the internal wall of the large intestine and for the identification of possible neoplastic masses along the colorectal tract, colonoscopy is also the ideal test for the collection of a sample of tumor cells, to be subsequently submitted to specific laboratory analysis (tumor biopsy).

As can be guessed from the brief description of the procedure, colonoscopy requires the sedation of the patient and is one of the invasive medical diagnostic procedures.

FLEXIBLE SIGMOIDOSCOPIA

Flexible sigmoidoscopy is the endoscopic examination aimed at visual exploration from the inside of the anus, rectum and sigma, in other words the last section of the large intestine.

From a procedural and instrumental point of view, it has many points in common with colonoscopy:

• It involves the use of an instrument equivalent to the colonoscope, called a sigmoidoscope ;
• Use the anal opening to insert the sigmoidoscope into the intestinal tract of interest;
• It uses an external monitor for the reproduction of what is "observed" by the sigmoidoscope camera;
• It allows to collect a sample of cells from a possible tumor mass, in order to subject them to specific laboratory analysis (tumor biopsy);
• Requires patient sedation.

Doctors prescribe flexible sigmoidoscopy as an alternative to colonoscopy - which is a test with greater exploratory capabilities - when they are fairly sure that the suspected tumor they are looking for resides in the sigma-ano tract.

BARIUM-SULPHATE-BASED CLISTER

Premise: in medicine, the term enema means the introduction of a liquid substance for laxative, therapeutic or diagnostic purposes into the colon-rectum of the intestine using a small tube inserted into the anal opening.

Also known as barium enema, the barium sulphate based enema is a radiological diagnostic procedure, which involves the introduction, according to the methods described above, of a contrast medium containing barium sulfate.

Barium sulfate is a substance that appears white on radiological images; therefore, after the time necessary for its deposition on the intestinal wall, it allows the radiologist to obtain images of the colon, sigma and rectum with good definition and sufficiently clear and detailed.

Although the barium sulphate enema cannot substitute, for efficacy, for colonoscopy, it is nevertheless an instrumental test with good diagnostic potential. In various circumstances, in fact, it is able to highlight the abnormal formations present on the intestinal wall, whether these tumors, polyps or ulcers.

VIRTUAL COLONSCOPY

Virtual colonoscopy is the radiological exam that exploits the potential of CT (or Computerized Axial Tomography ), to create highly detailed three-dimensional images of the large intestine.

Complementary to colonoscopy, this instrumental examination is painless, it does not include the introduction into the human body of instruments comparable to the colonoscope nor the administration of sedatives; furthermore, it is not absolutely necessary to inject a contrast agent.

The only procedural peculiarity to be reported is the following: shortly before its execution, the doctor inserts a very thin plastic tube, through which he practices, past the patient's anal orifice (therefore in the terminal part of the large intestine of the person under examination) an insufflation of air or carbon dioxide; the insufflation of air or carbon dioxide serves, in a certain sense, to "open" the intestine, so that the images created subsequently by the TAC are even clearer and full of details.

Like any radiological examination based on the principles of CT, even a virtual colonoscopy exposes the patient to a non-negligible dose of ionizing radiation and, therefore, is included in the list of minimally invasive diagnostic procedures.

Tumor biopsy

The tumor biopsy consists in the collection and histological analysis, in the laboratory, of a sample of cells from a tumor mass.

It is the most suitable test to define the main characteristics of tumors, including histology, cells of origin of neoplasia and staging .

On the occasion of a biopsy on a sample of cells belonging to a colon tumor, a pathologist and a gastroenterologist are generally concerned with histological analysis.

STAGING OF THE ADONOCARCINOMA OF COLON

The parameter " staging of a malignant tumor " includes all that information, collected during biopsy, which concerns the size of the tumor mass, its infiltrating power and its metastasizing capacities.

Accurately establishing the staging of a malignant tumor is essential to planning the most appropriate treatment.

For adenocarcinoma-type colon cancer, there is a staging (the so-called Dukes staging ) at 4 levels of increasing gravity, which doctors call stages and identify with the first four capital letters of the alphabet (A, B, C and D ).

The tumor characteristics for each single stage are the following:

• Stage A : the tumor resides almost exclusively on the intestinal mucosa (ie the innermost cellular layer of the intestinal wall); rarely, it goes into the layer below the mucosa.

  It never affects the lymph nodes, not even the closest ones (regional lymph nodes)

  Stage A colon cancer is the least severe.

• Stage B : the tumor mass has penetrated beyond the intestinal mucosa and affects the underlying layer of smooth muscle cells (the so-called muscle tunic).

  As with stage A, it never involves any lymph nodes.

• Stage C : the tumor has gone beyond the muscular habit, also invading the outermost layer of the intestinal wall and the first regional lymph nodes.
• Stage D : the tumor has affected most of the regional lymph nodes and has disseminated its tumor cells ( metastases ) in organs distant from the point of origin (eg: lymph nodes of the chest, liver, lungs, bones, brain, etc.).

  Stage D colon cancer is the most serious.

Screening and surveillance

The demonstration that colon cancer - adenocarcinoma of the colon in particular - arises quite frequently from an adenomatous polyp present for years in the colorectal tract, and that the removal of this polyp allows the implementation of an effective prevention, has allowed the drafting of effective screening and surveillance programs for the general population.

These programs consist of:

• For all individuals over the age of 50 without a familiarity with colon cancer, occult blood research annually and performing a colonoscopy once every 7/10 years;
• For all subjects with a family predisposition, the same two diagnostic tests mentioned above, but both with an annual frequency and starting from the age of 40-45;
• For children of people suffering from familial adenomatous polyposis and Lynch II syndrome, performing a colonoscopy as early as the age of 6-8 years and, if the polyps were numerous and at high risk of malignant transformation, the surgical removal of the entire colon ( total colectomy ).