Immunotherapy and targeted therapy give patients more options in the battle against gastrointestinal cancers.

In the past, gastrointestinal cancers such as colorectal cancer and stomach cancer were usually treated with surgery, radiation and/or chemotherapy. However, the advent of targeted therapies has had a significant effect of prolonging life for patients with these diseases.

Targeted therapies block the growth and spread of cancer by interfering with specific molecules that are involved in the growth, progression, and spread of cancer.

They are not a magic bullet though as the cancer cells eventually evolve and become resistant to these drugs.

Colorectal cancer

Colorectal cancer is cancer that originates from the colon (the longest part of the large intestine) or the rectum (the last several inches of the large intestine before the anus). Most colorectal cancers are adenocarcinomas, which are cancers that begin in cells that make and release mucus and other fluids.

Colorectal cancer is the most common cancer in Singapore and the incidence of this cancer has been steadily increasing. Singapore has one of the highest incidences of this cancer in Asia.

Thanks to the rise of targeted treatments, oncologists can now turn to targeted agents such as Avastin (bevacizumab) and Erbitux (cetuximab) which have been approved for use in fighting colorectal cancer that has spread.

Avastin works by blocking the growth of new blood vessels into the tumour. This deprives the cancer cells of nutrients and makes them more vulnerable to chemotherapy. Erbitux, on the other hand, in tumours which are sensitive to it, can block the signal that tells a tumour cell to grow.

Regulators have approved the use of Avastin against metastatic colon cancer as well as certain types of lung, ovarian, cervical, kidney and brain cancers. Erbitux has been approved for use against certain types of metastatic colon cancer as well as certain types of head and neck cancer.

Stomach cancer

Stomach cancer is the second leading cause of cancer death in both men and women around the world. In Singapore, it is the sixth most common cancer in men and the eighth most common cancer among women. About 300 people die each year from stomach cancer in Singapore.

Targeted therapy is now on the list of approved therapies for stomach cancer. The targeted therapies that are approved for stomach cancer are Cyramza (ramucirumab) and Herceptin (trastuzumab). Cyramza stops the growth of new blood vessels while Herceptin stops the growth of cancer cells that have too much of a protein known as HER2 on their surface.

"If you have a friend or relative with cancer who asks about what is the latest understanding and what is the latest treatment available, have that conversation with your doctor," said Parkway Cancer Centre's Medical Oncologist Dr Tan Wu Meng.

Immunotherapy

Another new form of cancer treatment is known as immunotherapy. Immunotherapy is a form of treatment that relies on the body's immune system to fight cancer. The body's immune system is already able to fight off bacterial and viral infections. Immunotherapy makes the immune system work against the cancer, said Dr Tan. "For example, some immunotherapies help remove the camouflage some cancer cells use to hide from the immune system," he added.

Another advantage is how it can keep on working for some time, even after treatment stops. "Once you wake up the immune system, in some cases, you are able to keep fighting." He described advances in immunotherapy as "a scientific revolution happening in front of our very eyes".

So far, immunotherapy has had the biggest impact in the treatment of melanoma and lung cancer. Trials are underway to examine its effectiveness in the treatment of gastrointestinal cancers.

Based on a presentation given by Dr Tan Wu Meng at a medical seminar organised by Channel NewsAsia and Parkway Cancer Centre.

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