Colon Cancer is an Important Public Health Problem

Colon cancer is a worldwide health problem that brings with it high morbidity and mortality. According to the American Cancer Society, the total number of new cases of colon cancer for 2013 is estimated to be around 102,480. In addition, it is also estimated that over 50,800 people will die in 2013 of colorectal cancer. It is these numbers and a lot more that make it a fairly important public health problem.

In this article we will cover colon cancer in a lot more detail, and discuss the treatment options available.

Etiology

There are a number of causes of colorectal cancer and are associated with risk factors. However, the etiological factors are not very clear cut, and below is a list of factors associated with development of colon cancer –

1. Family history of colorectal cancer – This is probably the most important cause.

2. APC gene mutation – Genetic mutations in a gene called the APC gene is one of the causes. Mutation in the APC gene causes familial adenomatous polyposis, which can give rise to colon cancer in the future.

3. Hereditary nonpolyposis colon cancer syndrome (HNPCC) – This is also called Lynch syndrome, and occurs due to a deficient mismatch repair (dMMR) of one of many genes. It can develop into colon cancer in the future.

4. Other risk factors – These include smoking, alcohol abuse and consumption of high quantities of red meat.

5. Inflammatory bowel disease – This includes ulcerative colitis and Crohn’s disease.

Clinical features

Patients with colon cancer are these days diagnosed even before they have symptoms due to the screening tests that relatives are put through should a family member be diagnosed with colon cancer. This means that many of them do not present with symptoms. However, some cases do go unnoticed, and patients who do develop colon cancer can complain of the following

  • Abdominal pain
  • Diarrhoea
  • Weight loss
  • Bleeding – blood on toilet tissue
  • Bowel obstruction
  • Anemia – usually iron deficiency anemia due to blood loss.

There are no specific signs on examination either. Patients may appear pale due to blood loss. On occasions a mass may be palpable in the abdomen as well.

Diagnosis

The diagnosis of colon cancer should be made early to prevent metastasis. There are a number of diagnostic techniques; some of them point towards a diagnosis while some confirm it and enable staging of the disease.

1. Blood tests – As patients with colon cancer lose blood, they will have a low haemoglobin and serum ferritin level. Blood markers such as serum carcino-embryonic antigen (CEA) will be elevated and carry prognostic implications.

2. Chest x-ray – This helps in assessing for lung metastasis. In some cases, a CT scan of the chest will need to be performed.

3. CT scan – This test will involve scanning both the chest and the abdomen to assess for local and distant spread.

4. Positron Emission Tomography (PET) scan – This test is becoming more and more popular these days given its usefulness in colon cancer staging. It has a high sensitivity at picking up metastasis.

5. Endoscopy – This is probably the most often performed test as it provides for direct visualization for the walls of the colon and the cancerous lesion. However, it is used these days for screening family members of patients with colon cancer. Tissue samples can be taken and analyzed to assess any histological changes in the cells or appearances suggestive of cancer.

The endoscopy tests performed include colonoscopy and flexible sigmoidoscopy.

Colon cancer appearance on endoscopy

Once a diagnosis of colon cancer is made, staging of the cancer is required to decide on treatment options.

Staging of colon cancer

A detailed staging analysis of colon cancer is out of the scope of this article. However, parameters that are assessed to determine stage of colon cancer (TNM staging) include-

  • Tumor size and extent – whether it invades different layers of the walls of the colon
  • Node size and numbers affected – Colon cancer can affect lymph nodes. Depending on the number of lymph nodes involves, it is staged.
  • Metastasis – This refers to spread to either nearby structures or distant structures.

The image below will provide a better picture on how staging is conducted –

TNM staging of colorectal cancer

Once TNM staging is complete, stage grouping is performed. This is illustrated in the table below –

Stage Group

TNM Stage

O

Tx,N0,M0

I

T1-T2,N0 M0

IIA

T3,N0,M0

IIB

T4a,N0,M0

IIc

T4b,N0,M0

IIIA

T1-T2,N1,M0; T1,N2a,M0

IIIB

T3-T4a,N1,M0;
T2-T3,N2a,M0; T1-T2,N2b,M0

IIIC

T4a,N2a,M0; T3-4a,N2b,M0;
T4b, N1-2,M0

IVA

Any T, Any N, M1a

IVB

Any T, Any N, M1b

 Stage grouping of colon cancer

Once staging is complete, it is decided what treatment options should be offered to the patient.

Treatment

Colon cancer can be treated medically or surgically or with both. Radiation therapy is also used.

1. Medical therapy

This consists of chemotherapy with 5-Fluorouracil. Other agents such as capecitabine may also be used as combination therapy or monotherapy, and long term survival rates have been shown to be good. Newer biological agents have been developed such as Bevacizumab which can be used in combination with 5-fluorouracil.

2. Surgical treatment

Surgery is the best available curative treatment for early colon cancer and for ones that have only limited spread. Depending on the site of the cancer, different parts of the colon are surgically removed.

  • If the right side of the colon is involved, a right hemicolectomy is performed.
  • If the transverse colon is involved, an extended right hemicolectomy is performed
  • If the left side of the colon is performed, a left hemicolectomy is performed
  • In case of involvement of the rectum, low anterior resection or a transanal resection is performed

In most cases of colon cancer, following surgery, post operative 5-fluorouracil is also prescribed.

Following surgery, patients may require a colostomy bag. Training is provided to learn how to use it at home.

3. Radiation therapy

This is usually offered as an adjunct to surgery. It can be either external beam radiation therapy or brachytherapy. Newer radiotherapy treatments are also offered these days.

Conclusion

Colon cancer can be a devastating diagnosis. Screening methods have made it easier to diagnose earlier or even to prevent it from manifesting. Treatment options are many but can have a drastic impact on the patient’s quality of life.