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From genomic profiling to targeted therapy, treatment for colorectal cancer has become more personalised over the last decade. Dr Zee Ying Kiat, Senior Consultant, Medical Oncology explains more.

Singapore has one of the highest numbers of colorectal cancer in Asia, along with China, Japan, Korea and Malaysia¹. Colorectal cancer is the most common cancer in Singaporean men, and the second most common cancer in Singaporean women, with a total of over 11,000 new cases diagnosed between 2015–2019².

The incidence of colorectal cancer in both men and women has been steadily increasing. Fortunately, the number of deaths resulting from colorectal cancer has also decreased over the last decade. This may be attributed to:

1. A rise in people getting screened for colorectal cancer, which can help detect cancer or precancerous conditions early, and;

2. Advances in colorectal cancer treatment, which has led to improved outcomes for patients, especially when the cancer is found in its early stages.

New ways of classifying colorectal cancer

If you are diagnosed with colorectal cancer, your doctor will assess the extent and stage of the cancer (based on whether the tumour has invaded nearby tissues, whether the cancer has spread, and to what parts of the body) to help plan the best treatment for your individual disease.

Genomic profiling has been a useful approach that allows doctors to tailor treatment to the characteristics of the cancer and genetic make-up of the individual patient. It involves studying the genetic information related to an individual person or specific cell type in a laboratory setting, to observe the way their genes interact with each other and the environment.

Genomic profiling may be used to determine why certain individuals get certain diseases while others do not, or why different individuals respond in different ways to the same drug. This information can then be used to develop new ways of diagnosing, treating, and preventing diseases such as colorectal cancer.

More personalised treatment for colorectal cancer

Colorectal cancer treatment is becoming more precise and personalised, contributing to the increase in survival rates for colorectal cancer over the last decade.

Here are some broad strategies for treating colorectal cancer:

• Surgery is the most common and effective treatment for colorectal cancer. It aims to completely remove the cancerous sections of the colon and/or rectum, as well as the surrounding tissue and mesenteric lymph nodes.

  Surgery has evolved over the years from open surgery to more precise procedures such as laparoscopic surgery (also known as keyhole surgery) to minimise the size of the incisions required. With smaller incisions, patients experience less pain and are able to recover more quickly from the surgery.

  Surgery may sometimes be followed by additional treatment with chemotherapy and radiation therapy to improve the patient’s chance of cure.

• Chemotherapy involves the use of chemical drugs to eliminate fast-growing cancer cells in the body. It can be used with curative intent, or for symptom control and prolongation of life.

• Radiation therapy uses linear accelerators to deliver high doses of radiation into the body to kill cancer cells and shrink cancerous tumours.

• Immunotherapy harnesses the body’s immune system to seek and destroy cancer cells in a way that is similar to vaccinations against viruses. This treatment can offer patients long-term control of the disease.

• Targeted therapy involves the use of drugs that are designed to target and block specific mutations that promote cancer cell growth and spread. Compared to conventional therapies, targeted therapy offers greater precision while reducing damage to healthy surrounding cells.

  Colorectal cancer has recently served as a proving ground for new targeted therapies. The use of such treatments to attack tumours with specific genetic profiles can add months to the lives of patients with incurable disease. There is hope that the development of additional targeted therapy drugs can continue to extend lives and cure more patients in the future.

Early detection is key

Generally, colorectal cancer is highly treatable in its early stages, before it has spread to other parts of the body. Early stage colorectal cancer is generally treated with curative surgery.

For advanced stage colorectal cancer, where the cancer has spread to other parts of the body, the mainstay of treatment would be chemotherapy, targeted therapy, and in some instances, immunotherapy. Surgery may also be considered in the palliative setting to relieve symptoms.

In a selected group of patients where the spread of colorectal cancer is limited to the liver, aggressive surgery to remove the primary cancer and affected area(s) of the liver may offer patients the prospect of cure.

Doctors may also often combine different treatments for greater effect, depending on the patient’s individual symptoms and overall health.

As with many cancers, early detection is key to beating colorectal cancer. Detecting colorectal cancer or precancerous conditions early allows patients to receive care at the earliest possible stage, leading to better outcomes. It is therefore important to undergo regular screening based on recommended population screening guidelines, to allow for early detection and intervention.

¹ _{“Prevalence and risk factors of colorectal cancer in Asia”, Wong, MCS, et al., 2019}

² _{Singapore Cancer Registry Annual Report 2019}