Colon Cancer - All the Information at a Glance

Colon cancer refers to a malignant tumor in the large intestine, small intestine, or rectum. This tumor develops when benign cells in the intestinal lining become malignant. In most cases, tumors develop in the large intestine or rectum. Tumors in the small intestine are extremely rare.

Doctors classify colorectal cancer using the following technical terms:

• Colon cancer refers to a tumor of the large intestine. Colon surgery deals with this form of colorectal cancer.

• Rectal carcinoma refers to cancer of the rectum. In this case, the tumor is located in the final section of the intestine.

• Colorectal carcinoma refers to tumors in the large intestine and rectum.

Colorectal cancer ranks second among the most common cancers in Germany for both men and women (Robert Koch Institute 2006).

In Germany, approximately 73,000 people are diagnosed with colorectal cancer each year, and about 28,000 people die from it. Statistically speaking, 6 out of every 100 people in Germany will develop colorectal cancer during their lifetime—that is, one in every seventeen of us.

Colorectal cancer usually develops from benign colorectal polyps. The transformation from a benign colorectal polyp (adenoma) to malignant cancer (carcinoma) takes many years (adenoma-carcinoma sequence).

This transformation is caused by a series of successive genetic changes (mutations) in the mucosal cells of the intestinal wall. These ultimately lead to a loss of control over cell growth, allowing the cells to divide unchecked and spread malignantly.

The process of transformation occurs in several stages:

The mucosal cells begin to overlap locally, gradually forming a small growth known as an adenoma. The most common manifestation of such an adenoma is a colorectal polyp. A polyp grows into the intestinal lumen as a visible bud. It can therefore be easily detected during a colonoscopy and, if necessary, removed.

Removal of a polyp during a colonoscopy | © Ortenau Klinikum, License: CC BY 3.0

If the polyp goes undetected, genetic changes in the cells accumulate until they eventually develop into malignant cancer cells. Once they begin to invade the surrounding tissue, this is referred to as “invasive” tumor growth.

The tumor cells slowly invade the entire intestinal wall. In addition, individual cells can break away and be carried by the blood or lymphatic fluid to other parts of the body. There, they can form secondary tumors (metastases). This entire process, from polyp to cancer, is estimated to take 5–10 years. The risk of such a transformation increases with age; most colorectal cancer patients are over 50 years old.

However, these genetic changes can also be inherited (approximately 20–30% of cases). As a result, cancer can develop even at a younger age. If there is a history of colorectal cancer in a family, special caution is therefore warranted.

Other factors that can alter genes and thus promote the development of cancer include, among others

• tobacco smoke

• excessive alcohol consumption

• obesity

• an unhealthy lifestyle and diet (low intake of fruits and vegetables, and lack of exercise)

• chronic inflammation (Crohn’s disease, ulcerative colitis)

• various chemicals

• radioactive radiation

• UV rays

Certain other types of cancer also increase the risk of developing colorectal cancer. These include, for example, breast or ovarian cancer.

In the early stages, colorectal cancer usually causes no or very few symptoms. As the disease progresses, the following early signs may appear:

• changes in bowel habits (alternating between constipation and diarrhea, changes in stool consistency, color, or odor, or a frequent urge to have a bowel movement)

• Blood in the stool

The presence of blood in the stool does not necessarily indicate colorectal cancer. Other conditions are much more common, such as

• hemorrhoids,

• polyps, or

• inflammation

are the cause. Nevertheless, these cases should always be investigated!

Other warning signs include

• a sudden drop in performance

• weight loss

• night sweats

• fever

However, such symptoms are by no means proof of colorectal cancer. They can also occur with other conditions. Therefore, a thorough evaluation is recommended.

The earlier colorectal cancer is detected and treated, the better the chances of recovery. Through regular screening, colorectal cancer can be almost completely prevented or cured. Everyone aged 50 and older can and should take advantage of the colorectal cancer screening program offered by public health insurance providers. Until age 55, you are entitled to a digital rectal exam and a fecal occult blood test once a year.

After turning 55, a colonoscopy is also offered as a screening measure, even if you have no symptoms. If there is a family history of colorectal cancer, the colonoscopy may need to be performed earlier. When detected early, colorectal cancer has a very good prognosis and can be completely cured.

Examination methods for screening or detecting colon cancer

First, the doctor performs a digital rectal exam. During this exam, the doctor palpates and assesses the rectum, the anal sphincter, and the prostate. Any abnormal findings from the digital rectal exam must be investigated further via a colonoscopy.

If necessary, further tests may follow. The goal is to:

1. to determine whether colorectal cancer is actually present (tumor detection),

2. and, if detected, to determine how far it has progressed (tumor staging).

During a detailed consultation, the doctor will ask about current symptoms, comorbidities, and risk factors.

Test for hidden blood in the stool (occult blood test, Hemoccult)

The rectum, the anal sphincter, and the prostate can be examined and assessed by digital rectal exam. Any abnormal findings on digital rectal exam must be clarified by a colonoscopy.

Test for hidden blood in the stool (occult blood test, Hemoccult)

Three consecutive stool samples are examined in the laboratory for blood that is not visible to the naked eye. If blood is detected in the stool, a colonoscopy must be performed for further evaluation.

Colonoscopy

Only a colonoscopy, in conjunction with the removal of a tissue sample, can reliably detect colon cancer. In addition, the doctor can identify colon polyps—which may be precancerous—and remove them immediately.

Depending on the section of the colon being examined and the endoscope (camera and light instrument) used, colonoscopy can be further subdivided into:

• Colonoscopy (flexible examination of the entire large intestine)

• Sigmoidoscopy (flexible examination of the lower large intestine and the rectum)

• Rectoscopy (rigid examination of the rectum up to approximately 15–20 cm)

Colonoscopy with Normal Findings | License: CC-BY-SA-3.0

X-ray diagnostics, CT, and MRI

These radiological procedures are not part of routine screening but may be important in specific clinical situations. Computed tomography (CT) and magnetic resonance imaging (MRI) produce cross-sectional images of the body’s interior. These images are processed using specialized computer software to create a three-dimensional view of the interior of the bowel.

In addition to the general assessment of the heart and lungs, a chest X-ray is also used to screen for possible colorectal cancer metastases in the lungs. CT can visualize not only the tumor itself but also any enlarged lymph nodes or metastases.

MRI does not use X-rays, but rather alternating magnetic fields. This technique provides the most precise depiction of a tumor’s extent and anatomy. This is important for surgical planning, for example, in cases of rectal cancer. As with CT, enlarged lymph nodes or other organ metastases (especially in the liver) can be clearly identified.

X-ray Examination (Barium Enema)

In a barium enema, the large intestine is filled with a contrast agent through the anus and visualized on X-ray images. However, inflammation and small polyps are more difficult to assess than during a colonoscopy. Added to this are the radiation exposure and the limited applicability of CT/MRI for patients with metal implants, pacemakers, or claustrophobia.

Abdominal Ultrasound

Ultrasound (sonography) is a simple and risk-free examination method for visualizing internal organs such as the liver, kidneys, or spleen. An ultrasound examination of the abdomen is used to determine whether colorectal cancer metastases are present in other abdominal organs (e.g., the liver).

Blood tests, including tumor markers (CEA)

Blood tests can be used to measure so-called tumor markers. Tumor markers are substances that are produced in greater quantities by tumor cells but can also be found in healthy individuals.

A negative or normal tumor marker does not rule out cancer, nor does an elevated tumor marker prove it. These values are therefore primarily used to monitor the course of the disease. An increase in these values following tumor surgery would indicate a recurrence of the disease.

The most important tumor marker for colorectal cancer is CEA (carcinoembryonic antigen).

Positron Emission Tomography (PET)

Cancer cells grow faster and therefore consume more energy and sugar than normal cells. Positron emission tomography makes this visible.

To do this, a labeled sugar is injected, which is taken up more readily by active cancer cells than by normal cells. A special scan then visualizes the different distribution of the labeled sugar.

PET is not part of routine screening for colorectal cancer but is used only in specific clinical situations. These include, for example,

• assessing response to chemotherapy or radiation therapy, or

• diagnosing recurrence.

Based on the test results, it is also possible to assess the risk associated with surgery (operability). This includes a thorough evaluation of the function of vital organs such as the heart and lungs.

Surgical removal of the tumor is the most important part of the treatment plan for colorectal cancer. Surgery is usually the only chance for a complete cure.

In general, however, a cure is only possible if the tumor cells have not yet spread to other organs. Only in certain circumstances is a cure still possible in such cases today.

For this reason, it is very important to conduct a precise assessment of the extent of the disease (staging) before any surgery.

Colon Cancer

In the case of colon cancer, surgery is performed as soon as possible after diagnosis and staging. The patient can only be cured if the tumor is completely removed.

To ensure this, the removed tumor is examined and further analyzed by a pathologist after surgery. The pathologist checks both the margins of the specimen and the lymph nodes that were removed along with the tumor.

Depending on the results, additional chemotherapy may be necessary afterward.

Rectal Cancer

In the case of rectal cancer, once the diagnosis has been made, the exact size and depth of invasion of the tumor must first be determined.

For smaller tumors, immediate surgical removal is recommended. For large tumors, pretreatment with chemotherapy and radiation therapy (or radiation therapy alone) is usually performed first to shrink the tumor.

This simplifies the surgery, reduces its risks, and lowers the risk of the tumor recurring after surgery.

Radiation therapy requires extremely precise planning. It is administered on an outpatient basis for a few minutes, 5 days a week, over a period of about 5 weeks. Side effects can occur here as well, including

• diarrhea

• skin irritation (dryness, redness)

• occasional skin discoloration

• Hardening of the subcutaneous fatty tissue

Whether additional chemotherapy is necessary after surgery depends on various histopathological criteria.

Radiation therapy (usually in combination with chemotherapy), however, is used only for rectal cancer. Before surgery (neoadjuvant), it is used to shrink the tumor, while after surgery (adjuvant), it is intended to prevent recurrence.

What information does the pathological examination of the surgical specimen provide?

After surgery, the pathologist’s work begins. The pathologist performs a histological examination of the surgical specimens. During this process, both the specimen and all removed lymph nodes are cut into very thin sections. This is followed by treatment with special stains that make it easier to identify tumor tissue.

Only these examinations can

• determine the exact size of the tumor,

• the depth of invasion, and

• the degree of differentiation

.

In addition, the pathologist examines the surgical margins to ensure they are free of tumor, thereby confirming that the tumor has been completely removed. The pathologist typically observes the surgery in person. This allows them to instruct the surgical team to remove additional tissue if necessary.

Tumor Classification

Important information can be obtained by examining the surgical specimen. This enables an accurate classification of the tumor.

This classification is known as the TNM classification. It reflects the individual extent of tumor involvement for each patient. This is crucial for determining further treatment. In the TNM classification, three factors are assessed as follows:

• T = Tumor: Used to assess the depth of invasion and the extent of tumor involvement in the individual sections of the intestine (T1 to T4)

• N = Nodus (lymph nodes): Used to assess regional lymph node metastases (N0 = none, N1 = few, to N2 = numerous). Lymph node metastases are generally associated with a poorer prognosis for the patient; therefore, subsequent chemotherapy is recommended starting at stage N1.

• M = Metastases: Used to assess distant metastases in other organs. The M stage is classified as M0 (= no metastases) or M1 (= metastases).

Tumor Stage

Based on the tumor findings and the resulting TNM classification, the tumor is staged according to UICC criteria. There are four stages, I–IV:

• Stage I: T1 or T2 N0 M0

• Stage II: T3 or T4 N0 M0

• Stage III: any T, N1 or N2, M0 (lymph node metastases present)

• Stage IV: any T, any N, M1 (presence of distant metastases)

In addition, “grading” is also assessed, which indicates the tumor’s differentiation. The degree of differentiation describes how similar the tumor tissue still is to its original intestinal tissue. The more degenerated the tissue is, the more aggressive the cancer:

• G1 = well-differentiated,

• G2 = moderately differentiated, and

• G3 = poorly differentiated.

Another important factor for prognosis and treatment is the R classification. It describes whether any residual tumor remains in the body (residual tumor status).

This involves assessing any metastases remaining in the body and the margins of the surgical specimen. The greater the distance between the margins and the tumor, the better the prognosis for the patient:

• R0 = no tumor visible on histological examination

• R1 = Histological evidence of residual tumor

• R2 = Residual tumor or metastases visible to the naked eye.

In tumor stages III–IV, additional treatment for recurrence or metastases may be considered following colorectal cancer surgery. Post-surgical follow-up care is planned and organized in consultation with all participating physicians. Prerequisites for this include

• a complete colonoscopy before or as soon as possible after colorectal surgery and

• an assessment of the patient’s general condition.

Whether and how often post-surgical follow-up is indicated in an individual case can only be determined once all test results are complete.

The goal of follow-up care is to detect as early as possible if

• the tumor begins to grow again (recurrence) or

• new secondary tumors (metastases) form.

The risk of this is highest in the first two years after colorectal cancer surgery. Regular checkups are therefore essential. After that, the risk of recurrence continues to decrease over time. The intervals between checkups can therefore be gradually extended:

• for colon cancer, every 6 months for the first 3 years, and annually in the 4th and 5th years;

• for rectal cancer, however, 3-month intervals are recommended in the first year.

After 5 years, colorectal cancer follow-up care can usually be discontinued.

What does follow-up care for colorectal cancer involve?

Basic follow-up care includes

• a consultation with the doctor

• a physical examination

• monitoring of blood test results

• measurement of the CEA tumor marker

• an ultrasound examination of the abdominal cavity

• A chest X-ray

Another integral part of follow-up care is a colonoscopy.

For colon cancer, it is recommended to undergo a colonoscopy once a year. For rectal cancer, a rectoscopy is particularly recommended at the beginning of each follow-up examination.

Computed tomography (CT) is not routinely used as part of colorectal cancer follow-up care. However, it can be helpful for establishing the baseline status after surgery, allowing even the smallest changes to be detected quickly.

Nutrition After Colorectal Cancer Surgery

Through diet, patients can specifically influence

• stool consistency,

• flatulence, and

• their general well-being

. However, there are neither mandatory dietary recommendations nor blanket prohibitions.

Avoiding Certain Foods

The basis of dietary therapy is the “light, balanced diet,” which involves avoiding foods and beverages that, based on experience, frequently lead to intolerances. These include

• legumes

• mushrooms

• cabbage vegetables

• raw onions

• garlic

• Leeks

• Fried foods

• Whole-grain bread with whole grains

• freshly baked bread

• hard-boiled eggs

• acidic foods

• Heavily fried foods

• Smoked foods

• Spicy foods

• Foods and beverages that are too hot or too cold

• carbonated beverages

• unripe fruit

It is recommended that you keep a food and symptom diary to assess your individual food tolerance.

Nutritional Recommendations

Sometimes, during colorectal cancer surgery, an artificial opening is created in the small intestine (ileostomy or jejunostomy). In this case, the large intestine no longer functions, which leads to reduced reabsorption of water and electrolytes. This results in loose, mushy stools and more frequent bowel movements.

It is important for the patient to know that every time they eat or drink, it triggers a bowel movement. Eating and drinking slowly, as well as chewing thoroughly, can be very helpful in this situation.

In the long term, it is recommended to switch to a Mediterranean diet. It not only helps prevent heart disease and obesity but also certain types of cancer. The Mediterranean diet includes

• daily and generous consumption of fruits, vegetables, and salad

• a preference for plant-based fats, such as canola, olive, or soybean oil

• reducing fat intake (dairy products in moderation, less frequent consumption of red meat and processed meats)

• frequent consumption of fish (2–3 servings per week)

• moderate alcohol consumption, if at all

In addition, the Mediterranean diet also includes

• a healthy lifestyle,

• taking your time and relaxing while eating, as well as

• regular physical activity

.

Do I need chemotherapy after colorectal cancer surgery?

If tumor-involved lymph nodes are detected, postoperative (adjuvant) chemotherapy is recommended.

In this case, although the tumor itself has been completely removed, there is still a risk (up to 50%) that individual cancer cells have already spread to other parts of the body. These cannot be detected using current methods.

Large-scale studies have shown that prophylactic (adjuvant) chemotherapy significantly reduces the risk of recurrence.

Other indications for adjuvant chemotherapy would include, for example, earlier tumor stages if

• the tumor ruptured during colorectal cancer surgery,
• the tumor exhibits poor cellular differentiation (G3), or
• fewer than 12 lymph nodes were removed during surgery.

In these cases, experts must decide on a case-by-case basis whether chemotherapy is indicated or not.

If colorectal cancer is detected only at a late stage, it has already metastasized. In such cases, so-called palliative chemotherapy is indicated. A cure is usually no longer possible at this point. The goal of treatment in this case is to improve quality of life and prolong survival.

In some cases, chemotherapy can shrink colorectal cancer metastases to the point where they can be surgically removed.

Chemotherapy targets cells that divide rapidly—such as cancer cells. Unfortunately, this also affects healthy tissue with a high division rate, such as hair cells. The blood distributes the drugs, also known as cytostatic agents, throughout the body, making this a “systemic therapy.”

Which drugs are used?

A wide variety of different drugs are now available. Oncologists select and combine them based on each patient’s individual case.

In most cases, several drugs are used according to a fixed, proven regimen (e.g., the FOLFOX regimen). Provided there are no health issues that would preclude it, chemotherapy can be administered on an outpatient basis. The implantation of a venous port catheter may be necessary for administering the medications. This makes treatment easier and more comfortable for colorectal cancer patients.

Adjuvant chemotherapy typically lasts half a year. However, in the metastatic stage, the duration of treatment may be extended depending on the patient’s response to therapy.

In these cases, in addition to traditional cytostatic drugs, so-called antibodies (e.g., cetuximab, bevacizumab) may also be used. Antibodies bind to specific surface structures on cancer cells that are important for tumor growth and block them. In standard “adjuvant” therapy, however, antibodies have not (yet) played a significant role.

What side effects can occur with chemotherapy?

The potential side effects of chemotherapy result from the fact that rapidly dividing healthy cells are also killed. However, they do not necessarily occur.

This includes, for example, the bone marrow, where various blood cells are produced, which can lead to

• anemia,
• bleeding, and
• infections

may occur.

White blood cells are the most important for fighting infections. It is essential to monitor them regularly (complete blood count) during chemotherapy. If their count drops too low, treatment must be interrupted to allow for a recovery period.

The digestive tract is also one of the rapidly dividing tissues. Chemotherapy can cause various side effects here. These include

• nausea
• vomiting
• Loss of appetite
• Altered sense of taste
• Diarrhea

Fortunately, there are some very effective medications available to treat these side effects (e.g., antiemetics).

Another possible side effect of some cytostatic drugs is hair loss. However, complete hair loss is not expected with the drug combinations used to treat colorectal cancer.

In any case, the hair will grow back after treatment ends. The other side effects mentioned above also disappear once treatment is complete.

With the antibodies mentioned earlier, there are generally few side effects to worry about. Since they are proteins, allergic reactions can rarely occur (e.g., acne-like rash with cetuximab). In general, your treating oncologist should inform you about the side effects to be expected based on your treatment regimen. If necessary, they will treat these side effects with additional medications.

Research has shown that there are no universal factors that improve or worsen our quality of life. The term “quality of life” refers to the personal experience of having cancer. This includes feelings and symptoms related to emotional, physical, and social well-being.

There are therefore significant differences among individuals in how they cope with the disease. Each patient processes the stress caused by the disease or treatment differently.

Many of these stresses are temporary, but they can also persist and require psychological treatment.

During hospitalization, fear of surgery is often the primary concern. It is important to ask as many questions as you wish to know and understand during discussions with your treating physician. You should also address your own anxieties and concerns. After being discharged from the hospital, the many demands often lead to feelings of being overwhelmed. The main concern for many cancer patients is that the disease might recur or spread (“fear of progression”). This concern is normal and appropriate, but it can also become overwhelming.

In this situation, it can be helpful to talk about it and confront the fear. The importance of psychological coping with illness is increasingly recognized. As a result, there are now a wide variety of support options available in psycho-oncology.

The overall prognosis for colorectal cancer depends primarily on how completely the tumor could be removed. The earlier the tumor is detected and removed, the better the chances of a cure.

Thanks to improved screening programs, over 50% of cases are curable today. However, if colorectal cancer metastases are already present in other organs or lymph nodes at the time of diagnosis, the prognosis is significantly worse.

Specialists in colorectal cancer typically come from the departments of visceral surgery and/or gastroenterology. These two departments collaborate in the treatment of colorectal cancer, particularly with the following specialties:

• oncology,
• radiation oncology,
• radiology, and
• pathology.

In addition to these medical specialties,

• pain management and physical therapy,
• specialized oncology nursing, and
• so-called supportive care

play a major role. Supportive care includes, among other things,

• pastoral care,
• psycho-oncology,
• social services,
• nutrition counseling, and
• self-help groups.

The latter support colorectal cancer patients and their families throughout the entire treatment process.