Cancer Type

colorectal cancer Introduction

Colorectal cancer is the most common cancer in Hong Kong. Treatment costs vary depending on factors such as the time of diagnosis, the location and condition of polyps and tumors. Understanding the types of colorectal cancer, risk factors, and treatment methods can help us prevent this high-risk and deadly disease.

The large intestine consists of the colon and the rectum, and is about 150 centimeters long. The colon is located in the abdominal cavity, extending upwards from the cecum in the lower right abdomen to the ascending colon; then it crosses the entire abdomen to the left, called the transverse colon; then it descends to the lower left abdomen, called the descending colon; then it connects to the sigmoid colon, and finally the rectum and the anus.

The wall of the large intestine has four layers, from the inside out: the mucosa, the submucosa, the muscle layer, and the serosa.

The main function of the colon is to absorb the water and electrolytes remaining after food has been digested in the stomach and small intestine, which then slowly forms feces, which are propelled into the rectum by intestinal peristalsis. The rectum is a short section of the intestine connecting the sigmoid colon and the anus, about 12 to 15 centimeters long, and its main function is to store feces.

iI. Types of colorectal cancer

Colorectal Canceris a malignant tumor that forms in the tissues of the colon or rectum.

When a malignant tumor grows in any part of the colon, it is called"colon cancer"; if the tumor grows in the rectum, it is called"rectal cancer".

In Hong Kong, colorectal cancer is the most common cancer among the top ten cancers. According to data from the Hong Kong Cancer Registry, there were 5,634 new cases of colorectal cancer in 2018, with 2,314 deaths.

Early detection leads to a survival rate of over 90%.

Compared to other cancers, such as lung and liver cancer, colorectal cancer has a relatively high cure rate and survival rate. According to research from the University of Hong Kong's Faculty of Medicine, the 5-year survival rate (the chance of surviving 5 years after diagnosis) for stage I colorectal cancer patients can exceed 90%. Conversely, the 5-year survival rate for stage IV colorectal cancer patients is only 8%. The cost of colorectal cancer treatment, patient survival rate, and recurrence rate are all significantly influenced by the timing of diagnosis and treatment.

Issue 1

>90%

Issue 2

55％－70％

Issue 3

25％－55％

Issue 4

Like many other cancers, early-stage colorectal cancer may be completely asymptomatic. By the time symptoms appear, the tumor has actually been growing in the body for some time, and the disease may have already progressed to an intermediate or advanced stage (stage three or four). The clinical symptoms vary depending on the location of the tumor.

Common symptoms of colorectal cancer include:

Bloody stool
Change in stool habits
Change in stool pattern
Unclear bowel movements
Abdominal distension and abdominal pain
Anemia
Unexplained weight loss
Tired

iii. Risk factors for colorectal cancer

Colorectal cancer treatment can place a significant financial burden on patients, and its causes are closely related to lifestyle and diet. In fact, weight, dietary habits, and exercise habits are more closely associated with colorectal cancer than with other cancers. The following are risk factors for developing colorectal cancer:

Modifiable risk factors

Obesity: Overweight (BMI 25 to 29.9) or obese (BMI 30 or above), especially those with excessive waist circumference, have a higher risk of developing colorectal cancer.
Lack of exercise：Regular exercise (equivalent to 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity exercise per week for adults) may reduce the risk of colorectal cancer.
Eating habits：Excessive consumption of red meat and processed meats (such as bacon, sausages, and luncheon meat) increases the risk of colorectal cancer. In addition, meat cooked at very high temperatures (frying, baking, or grilling) produces carcinogenic chemicals, and excessive consumption of such foods may increase the risk of colorectal cancer.
Smoking：Studies have found that smokers have a 20% higher risk of developing colorectal cancer than never-smokers, and data also shows that male smokers face a higher risk than female smokers. Even those who have quit smoking still have a higher risk of colorectal cancer than never-smokers.
Excessive intake of alcohol：Colorectal cancer is associated with moderate to heavy alcohol consumption. It is recommended that men drink no more than two drinks per day and women no more than one drink per day.

Unchangeable risk factors

Age growth：The risk of developing colorectal cancer increases with age. While younger adults can also develop colorectal cancer, it is more common in people over 50.
Individuals who have had colorectal cancer:People with a history of glandular polyps (adenomas) have an increased risk of developing colorectal cancer. Patients should be especially vigilant if the polyps are large, numerous, or show cellular abnormalities. Furthermore, those who have had colorectal cancer (especially at a young age) have a higher chance of developing cancer in other parts of the colon, even if the tumor has been completely removed.
A close relative with a history of colorectal cancer or colorectal glandular polyps:If you have an inflammatory bowel disease, such as ulcerative colitis or Crohn's disease, you should start colorectal cancer screening early and regularly.
Close relatives have suffered from colorectal cancer or glandular polyps of the large intestine：Approximately one-third of colorectal cancer patients have a family history of the disease. Furthermore, colorectal glandular polyps can develop into cancer. If you have this family history, your risk of developing colorectal cancer increases.
Genetics: A small percentage of colorectal cancer cases are hereditary. The most common hereditary colorectal cancers are Hereditary Nonpolyposis Colorectal Cancer (HNPCC) and Familial Adenomatous Polyposis (FAP). HNPCC and FAP account for approximately 5% of all colorectal cancer cases, and there is a 50% chance of passing these genes on to the next generation if a person carries them.

iV. Diagnostic method

Early detection and accurate diagnosis can improve the effectiveness of colorectal cancer treatment and reduce costs. Doctors typically use the following methods to examine for and diagnose colorectal cancer:

Blood test

A blood test is performed to check the number of red blood cells to determine if the patient has anemia, and the level of carcinoembryonic antigen (CEA) in the patient's blood is also tested.
CEA is a tumor marker used in colorectal cancer. In approximately 80% of colorectal cancer patients, cancer cells produce additional CEA, causing elevated CEA levels in the blood. However, the sensitivity of CEA is only about 46%. Therefore, we cannot rely solely on CEA levels to diagnose colorectal cancer.
The ideal reference value for CEA is generally no higher than 5 μg/L. However, smoking and other health conditions, such as colitis, hepatitis, and cirrhosis, as well as cancers of other organs, such as breast cancer, lung cancer, and pancreatic cancer, can all cause elevated CEA levels. Therefore, the primary role of CEA is to monitor the effectiveness of colorectal cancer treatment and track recurrence.

Fecal occult blood test

Check for blood in the patient's feces.

Colonoscopy and tissue biopsy

A colonoscope is a flexible tube about 1.6 meters long, as thin as a finger, with a high-resolution lens at the end. It is inserted into the rectum through the anus and travels through the sigmoid colon, descending colon, transverse colon, ascending colon to the cecum and the terminal small intestine for a detailed examination. Through endoscopic images, doctors can directly observe the mucosa of the entire large intestine. If polyps or lesions are found during the examination, tissue can be immediately extracted or the polyp can be removed for pathological examination. It is the ideal diagnostic tool for colorectal cancer. Before the examination, the doctor will administer sedatives and painkillers to the patient, allowing them to undergo the examination while asleep. The entire process takes approximately twenty to thirty minutes.

Tumor molecular detection

Molecular testing is performed on tumor samples to determine if the tumor carries specific gene mutations. The test results may help doctors develop a treatment plan for colorectal cancer.

Contrast examination

These include magnetic resonance imaging (MRI), computed tomography (CT) scans, and positron emission tomography (PET) scans, which are used to diagnose the size and location of tumors and whether they have spread to other parts of the body.

V. Treatment methods

With advancements in medicine and technology, there are increasingly more treatment options for colorectal cancer, including:

Surgery
Radiation therapy (also known as "electrotherapy")
Chemotherapy (also known as chemotherapy)
Targeted therapy
Immunotherapy

Doctors will develop the most personalized treatment plan based on the stage of the disease, the size and location of the tumor, the patient's age, overall health condition, and their expectations for treatment and quality of life. Sometimes, more than one of the above treatment methods may need to be combined. The treatment plans for colon cancer and rectal cancer will also be different.

Surgical treatment for colorectal cancer

Surgical intervention is the primary treatment for colorectal cancer. The purposes of surgery include:

Radical surgery

The primary tumor of the large intestine, along with adjacent mesentery and lymph nodes, is removed. If there are a few distant organ metastases that do not involve a wide range of areas, they can also be removed at the same time. Then the intestine is reconnected.

Palliative surgery

Although colorectal cancer cannot be cured, palliative surgery may be considered to alleviate symptoms such as intestinal obstruction or bleeding.

Different surgical methods for colorectal cancer

Endoscopic polyp removal surgery

If the cancer is still confined to the form of a polyp, the polyp can be removed via colonoscopy.

Transanal endoscopic surgery

It is mainly used for the removal of mid- and low-lying rectal tumors. Using specialized equipment, tumors no more than 12 centimeters from the anus can be locally removed transanally. Because the surgical site is close to the anus, entering through the anus allows for a clearer view of the tumor, enabling complete removal and better avoiding damage to nerves or sphincter muscles during the procedure, thus preserving the anus's function of controlling defecation.

Traditional laparotomy

Laparoscopic (minimally invasive) surgery

Laparoscopic surgery is a type of minimally invasive surgery. Surgeons make several small incisions of about 0.5 to 1 cm in the patient's abdomen, and one incision of about 5 cm to remove the tissue. Compared to traditional open surgery, laparoscopy allows for a clear and detailed view of the abdominal cavity, especially the anatomical structures of the pelvic cavity. Therefore, the advantages of laparoscopic surgery include greater precision, smaller incisions, less bleeding, and less postoperative pain for the patient. However, laparoscopic surgery requires complex techniques and must be performed by experienced surgeons. The treatment outcomes (survival rate and recurrence rate) are similar to those of traditional open surgery.

Single-port laparoscopic surgery

Single-port laparoscopic surgery is a major breakthrough in minimally invasive colorectal cancer surgery. Its biggest difference from traditional laparoscopic surgery is that it is performed through a small incision of about 3 centimeters. After the surgery, the removed intestine is then removed from the body through the same small incision.

Single-port laparoscopic surgery minimizes abdominal wall incisions, further reducing surgical trauma and postoperative pain. It not only accelerates recovery but also contributes to the ideal of scarless surgery, as most surgeons design the incision at the navel. It is important to note that this procedure requires a high level of skill and must be performed by a highly experienced surgeon.

While laparoscopic (minimally invasive) surgery has many advantages, it is not suitable for all colorectal cancer patients. The following conditions are generally unsuitable for laparoscopic (minimally invasive) surgery:

Colorectal cancer causing acute intestinal obstruction

Intestinal perforation causing peritonitis

The tumor is too large

The tumor has invaded adjacent organs or metastasized to the peritoneum.

The patient has poor cardiopulmonary function.

The patient has abnormal blood clotting function or cirrhosis.

Rectal resection surgery

Since the introduction of mechanical suture devices, sphincter-preserving rectal cancer resection surgery has become increasingly common. Preoperative concurrent chemoradiotherapy in suitable patients also significantly increases the chances of sphincter preservation.

Regarding "ostomy"

Sometimes, rectal cancer patients may need to have a stoma created in their abdomen after surgery to replace the function of the anus. A stoma is an opening made in the abdominal wall to allow feces to pass through and be collected in an external ostomy bag.

Other treatments for colorectal cancer

In addition to surgical treatment, radiation/drug therapy, or a combination thereof, may be chosen when appropriate:

Radiotherapy

Radiotherapy, also known as electrotherapy, is a localized treatment that uses high-energy radiation to focus on the tumor site to destroy cancer cells, thereby preventing their growth and division.

Radiation therapy can be used to shrink tumors before surgery, making the surgery easier and reducing surgical trauma; it can also be used after surgery to further remove residual cancer cells in the body.

For patients with rectal cancer, preoperative radiotherapy is often used in conjunction with chemotherapy. The entire treatment course lasts about one month. Patients need to receive more than ten minutes of radiotherapy every day from Monday to Friday. The purpose is to shrink the tumor. Surgery is performed about four to six weeks after the completion of the treatment course, with the aim of preserving the anus.

For patients with advanced colorectal cancer, the purpose of radiation therapy is to relieve the patient's symptoms, such as reducing pain.

Chemotherapy

Chemotherapy, also known as chemotherapy, uses chemical drugs to destroy the growth and division of cancer cells. Chemotherapy drugs are administered intravenously or orally, and patients may need to receive more than one chemotherapy drug simultaneously. For colorectal cancer, chemotherapy can be divided into preoperative lead chemotherapy, postoperative adjuvant chemotherapy, and palliative chemotherapy.

Lead chemotherapy

In some cases of locally advanced or stage IV metastatic colorectal cancer, doctors may recommend that patients receive neo-adjuvant chemotherapy in conjunction with targeted therapy before surgery. After the tumor shrinks, the efficacy will be reassessed to determine whether the patient can undergo radical surgical treatment.

For patients with rectal cancer, lead chemotherapy is often used in conjunction with radiotherapy to reduce the size of the rectal tumor before surgery, with the aim of preserving the anus.

Adjuvant chemotherapy

For patients with stage II high-risk colorectal cancer and stage III colorectal cancer, it is generally recommended to administer adjuvant chemotherapy after surgery. Studies have shown that this can reduce the risk of recurrence by about 40% and significantly prolong the survival rate compared to patients who only undergo surgery.

For patients with rectal cancer, lead chemotherapy is often used in conjunction with radiotherapy to reduce the size of the rectal tumor before surgery, with the aim of preserving the anus.

Pain relief chemotherapy

Palliative chemotherapy is suitable for patients with locally advanced, unresectable colorectal cancer, as well as stage IV colorectal cancer. The goal of treatment is to control the disease and alleviate symptoms, rather than to cure it.

Targeted therapy

Targeted therapy is a drug that targets receptors, genes, signaling pathways, and angiogenesis factors associated with tumor growth. Targeted drugs only target specific "markers" on cancer cells, and because of this specificity, they have less impact on normal cells compared to traditional chemotherapy.

Currently, targeted drugs suitable for treating colorectal cancer can be broadly classified into the following two categories:

Class I anti-angiogenic targeted drugs

By inhibiting angiogenesis in cancer cells, the tumor's growth is cut off, causing it to die, and reducing the metastasis of cancer cells to other parts of the body via newly formed blood vessels.

Class II Epidermal Growth Factor Receptor Inhibitors

Its function is to block the transmission of tumor growth signals, thereby preventing or slowing the growth of cancer cells.

However, not all targeted therapies are suitable for all colorectal cancer patients. The key lies in whether the patient's cancer cells carry specific tumor genes. Before prescribing targeted drugs, doctors perform genetic testing on the tumor cells to screen for suitable drugs. For example, if the tumor is confirmed to have a RAS gene mutation, it can be determined that it is ineffective against the aforementioned type 2 targeted drugs.

Doctors often recommend that patients with advanced colorectal cancer use targeted therapy in conjunction with chemotherapy.

Immunotherapy

In the case of colorectal cancer, immunotherapy is only applicable to certain cases of advanced metastatic or recurrent colorectal cancer that have been tested and confirmed to be positive for specific gene changes, such as "high microsatellite instability" (MSI-H) or mismatch repair gene deficiency (dMMR).

HER2陽性大腸癌患者接受tucatinib標靶治療，展現個人化精準醫療的突破性效果

Breakthrough in targeted treatment of Tucatinib: New hope for HER2-positive colorectal cancer

Breakthroughs in the treatment of colorectal cancer in the fourth phase, successful cases: HER2-positive patients used the targeted treatment combination of tucatinib and trastuzumab to achieve no signs of disease after one year. The complete course from the failure of chemotherapy to the success of targeted therapy demonstrates the importance of genetic testing to guide personalized treatment. Learn about the efficacy of tucatinib in HER2-positive colorectal cancer and how targeted therapy can bring new hope and improved quality of life to patients with advanced cancer.

September 7, 2025