Colorectal Cancer

Colorectal cancer is one of the most common cancers in Hong Kong, with a total of 5,036 new cases in 2015, accounting for 16.6% of the total number of new cancer cases, of which 2,891 were men and 2,145 were women, with a ratio of 1.3 to 1. Based on the number of new cases, colorectal cancer is the second most common cancer among men in Hong Kong. 

Referring to the data from 2009 to 2013, the incidence rates of both genders started to increase at the age of 30; up to the age of 50, the incidence rates of both genders were very similar, but the increase in the incidence rate of females started to lag behind those of males, with the greatest difference between the two genders at the age of 80, which was around 500 for males and 350 for females per 100,000 population. 

After the age of 80, the morbidity rate for both sexes begins to drop. As for the mortality rate, it rises for both sexes from the age of 40 onwards, with females lagging behind males until the age of 85, where the mortality rate is close to 400 for males and less than 300 for females per 100,000 population.

Common symptoms of colorectal cancer include:

• Abdominal distension
• Intestinal colic
• Sudden change in bowel habit, e.g. diarrhoea or persistent constipation, stools become streaky, etc.
• Blood in the stool
• Black coloured stools with mucus
• Bleeding from the rectum
• Failure to pass stools that feel like they have not been emptied yet
• Weight loss
• Symptoms of anaemia, such as cold hands and feet, rapid heartbeat, pale face, dizziness, etc.

Colorectal cancer may not have obvious symptoms in the early stage. If you experience any of the above symptoms, you should seek medical advice as soon as possible to check if you have colorectal cancer.

Colorectal cancer is mainly caused by poor lifestyle habits, especially in diet, such as eating too much food containing high animal fat but not enough fibre-rich fruits and vegetables, or eating barbecued or processed meat frequently, which will increase the risk of colorectal cancer. Long-term lack of physical exercise and bad habits such as smoking and alcohol abuse are the main causes of colorectal cancer.

In addition, personal medical history is also a risk factor. People with chronic inflammation or polyps in the colon are more likely to have colorectal cancer than others. In addition, if someone in the family has suffered from colorectal cancer, other family members who are related by blood, such as siblings and children also have a higher chance of suffering from colorectal cancer.

In view of the above risk factors associated with colorectal cancer, to prevent colorectal cancer, the first step is to improve your lifestyle, such as eating more fruits, vegetables and whole grains that are rich in vitamins, minerals and fibre; drinking alcohol only in moderation if necessary; and developing a habit of regular exercise, trying to do at least 30 minutes of exercise every day to maintain a healthy body.

In general, doctors recommend colorectal cancer screening for people aged 50 or above. As colorectal cancer may not show obvious symptoms in its early stages, people without symptoms can undergo colorectal cancer screening first to find out if they are at higher risk or even if they have already developed the disease, so that they can receive treatment as early as possible.
 

If you notice symptoms of colorectal cancer, you should seek medical advice and examination as soon as possible. Doctors usually use the following methods to check whether a patient has colorectal cancer.

• Rectal examination

This is the first step to check if a patient has colorectal cancer. The doctor will put on gloves and insert a finger into the rectum to check for lumps or swelling.

• Endoscopy

An endoscopy is used to look directly inside the colon to see if there are any abnormalities. The patient should abstain from eating high-fibre foods for a few days, take laxatives and drink plenty of water the day before the test. During the examination, an endoscope is passed through the anus into the large intestine. If necessary, a sample of cells may be taken for biopsy.

• Barium enema

This is an X-ray examination of the large intestine. Prior to the examination, a bowel wash may be required, in which water is pumped into the rectum through a flexible tube and then expelled from the body. During the official examination, a contrast medium containing barium is poured into the rectum to give a clear projection of the large intestine, which is then analysed by the doctor.

In addition to the above tests, further tests will be performed to see if the tumour has spread to the lungs and liver.

• Liver Function Test

Blood tests are done to measure the chemical response of the liver. Any abnormalities may indicate that the cancer has spread to the liver.

• Chest X-ray

To see if the cancer has spread to the lungs.

• Computed Tomography

A computerised radiography (CT) scan uses X-rays to create a three-dimensional image of the body, which is much more informative than a flat X-ray film and can help the doctor make a diagnosis.

• Ultrasound

The doctor moves a small probe around the abdomen. The sound waves emitted by the probe are analysed by a computer and converted into images of the abdominal cavity and liver.

• Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) uses a magnetic field to create cross-sectional images of the body to look at internal tissues.

Through these tests, the doctor will stage the patient's condition. Colorectal cancer is generally classified into the following four stages:

There are three main treatments for colorectal cancer, namely surgery, chemotherapy and radiotherapy. In the early stage of colorectal cancer, surgery alone can be used to remove the cancer cells. However, in the later stage of colorectal cancer, it depends on the condition of the cancer cells: if the cancer cells have not spread, chemotherapy and radiotherapy can be used in addition to surgery; if the cancer cells have spread, chemotherapy can be relied upon to control the disease.

• Surgery

The surgeon will choose the appropriate surgery according to the shape and size of the tumour. One of the most common treatments is colon or rectal resection, in which the diseased portion and adjacent lymph nodes are removed and the ends of the large intestine are connected. However, there is a chance that the bowel may not be able to be connected, so the end of the bowel is connected to the outside of the abdominal cavity to serve as a bowel evacuation tube and is temporarily covered with a pouch to collect faeces. If the cancer has spread to the lungs or liver, the following surgeries may be performed:

• Radiofrequency Cautery

A needle electrode is inserted into the liver where the cancer is located and an electric current is emitted to destroy the cancer cells with high temperature.

• Microwave ablation

The same procedure is used to kill the cancer cells, but microwaves are used instead.

• Cryotherapy

A device is inserted into the cancerous tumour to kill the cancer cells by lowering the local temperature.

The sooner the patient can start moving around after surgery, the better the recovery will be, but a urinary catheter may be needed for the first few days to help with urination, or a drain may be placed in the wound to remove secretions. Drinks should not be consumed until bowel movement has returned to normal, and then, two to three days after surgery, small amounts of boiled water can be consumed, with portion sizes gradually increasing; after four to five days, lighter foods can be consumed.

After colorectal cancer surgery, patients can resume normal sexual life, but some male patients may be unable to have an erection or ejaculate because the nerves connecting to the sex organs were touched during rectal resection, which is rare and may only be temporary.

• Chemotherapy

Simply called "chemotherapy", it uses drugs to kill cancer cells, which divide faster than normal cells. The drugs are usually administered through a vein in the arm or through a catheter in the chest, where they are dissolved into the bloodstream and travelled throughout the body, searching for cancer cells and killing them along the way. Treatments are usually given two to three weeks apart, and the amount depends on the disease and the patient's response to the drugs.

In some cases, after surgery to remove a cancerous tumour, the cancer has metastasised to a nearby lymph node, or the doctor assesses that there is a high chance of recurrence, and other treatments are needed. The chemotherapy used at this time is called "adjuvant chemotherapy" to reduce the risk of recurrence.

Patients may experience various side effects after treatment, such as fatigue, hair loss, nausea and diarrhoea. In addition, individual chemotherapy drugs, such as Flurouracil, may cause redness, swelling and pain in the palms of the hands and heels, but these do not usually last long.

• Targeted therapy

Targeted therapy is also a type of anti-cancer drug that can be used in conjunction with chemotherapy to enhance the effectiveness of the treatment or prolong the patient's life. Although the side effects of targeted drugs are relatively mild, they may also affect the body, depending on the type of drug: EGFR inhibitors [Note 2] may cause fever, muscle pain, and even respiratory distress and shock after the initial injection; vasopressors [Note 3] may cause hypertension, proteinuria, and even vascular embolism. 

• Radiotherapy

Radiotherapy, commonly known as "electrotherapy", uses high-energy rays to destroy cancer cells. It can focus on the cancerous tumour and avoid damaging normal cells. As it is a localised treatment, areas not touched by the rays will not be affected. Before radiotherapy is administered, the doctor will mark the patient's skin to ensure that the rays will reach the exact target inside the body.

For colorectal cancer, radiotherapy is more commonly used for rectal cancer and less often for colon cancer. Electrotherapy is given before surgery if the doctor assesses that surgery would be difficult or if the cancer is in a more advanced stage after a scanning assessment. After surgery, some patients still have a higher risk of recurrence and may require radiotherapy. In addition, if the patient's health condition permits, radiotherapy and chemotherapy can be used together to enhance the therapeutic effect, but at the same time, there will be an increase in the number of side effects.

After receiving radiotherapy, patients may experience a variety of side effects, including nausea, diarrhoea, fatigue and skin irritation. In addition, if electrotherapy involves large areas of bone marrow, it may reduce the number of white blood cells, platelets and red blood cells, making the patient susceptible to infection, bleeding or anaemia. In this case, patients should have sufficient rest to avoid injury or dizziness.

In terms of sexual function, electrotherapy in the pelvic area may cause loss of ovarian function, permanent menopause and symptoms such as hot flashes, sweating and dryness of the vagina in females, while testicles in males may lose their sperm-producing function, resulting in infertility. Electrotherapy may also cause inflammation of the bladder lining, or redness, pain or even ulceration of the skin of the genitals and perineum, causing painful urination and affecting sexual behaviour. The extent of side effects depends on the dosage of electrotherapy and the duration of treatment, but most of the discomfort can be relieved with medication.

After receiving treatment for colorectal cancer, patients should discuss with their doctors and make arrangements for follow-up treatment and follow-up consultation according to their individual conditions, so as to detect any recurrence or anomalous tumour and provide timely treatment, and at the same time, manage other complications arising from the treatment, so as to speed up the progress of recovery. Patients should also change their dietary habits, avoiding high-fat foods that are difficult to digest and foods that irritate the intestinal tract. 

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1. A contrast agent is injected through a blood vessel and travels with the bloodstream to the organ to weaken the X-ray rays and make the tissue more visible.
2. EGFR inhibitors are a type of targeted drug that is used to block cancer cells from receiving messages that direct their growth and cause them to die.
3. Vasculosuppressants are targeted drugs that make it difficult for cancer cells to grow blood vessels so that they do not receive nutrients and die.

1. Cancer Fund: Understanding Cancer: Colorectal Cancer from https://heal-oncology.com/cancer/colorectal-cancer/