A diagnosis of colorectal cancer is always bad news, but with the recent developments in cancer therapy, patients with this cancer can find a ray of hope. Dr. Beatrice J. Tiangco, a medical oncologist at The Medical City, details the exciting breakthrough of newer targeted therapy, which may be combined with standard chemotherapy to improve the survival rates of patients with colorectal cancer
Dr. Beatrice J. Tiangco, MD, MSCE, FDCP, FPSMO, FPSHBT, is the head of the section of medical oncology and the consultant director of the chemotherapy unit of The Medical City. She’s also the assistant director of the Center for Cancer Care and Research of the
Colorectal carcinoma (CRC) is the third most commonly diagnosed cancer in males and the second in females. In the year 2008, there were over 1.2 million newly diagnosed cases worldwide and there were over 600,000 deaths due to this disease.
In the Philippines, roughly 8,500 new colorectal cases were diagnosed in 2012, and nearly 5,000 colorectal patients died of complications of their disease. It is unclear why, but data shows that mortality from CRC is around 25 percent higher in men than in women.
Certain familial conditions like familialpolyposis and Lynch syndrome lead to higher risk of developing CRC. A personal or family history of sporadic CRCs or adenomatous polyps likewise increases the risk for future development of CRC. Other observed risk factors are diabetes and insulin resistance, history of abdominal radiation, and to a lesser extent, cholecystectomy and high alcohol consumption.
Early warning signs and symptoms
Early in the natural course of colorectal cancer, the cancer cells are seen only within the sites of origin in the lumen of the large intestines or may penetrate deeper and deeper into the layers of the muscular walls of the colon.
Unless removed, the cancer may also be seen in enlarged lymph nodes surrounding the original mass. Beyond thesurrounding lymph nodes, cancer cells may pass through the lymph or blood vessels and form malignant tumors in the abdominal cavity, liver, lungs, or in women develop “drop” metastases to the ovaries and may be mistaken as ovarian carcinoma.
Early signs and symptoms may include alternating constipation and diarrhea, blood in the stool, stools that are smaller and rounder or thinner and longer, gassiness, fatigue, unexplained weight loss.
A physician will usually order a complete blood count and note anemia, likely due to a bleeding mass in the colon or rectum. Stool analysis may show microscopic or visible blood, a colonoscopy will show the cancerous mass which may or may be bleeding.
Colorectal cancer is considered to be in the early stage as long as it has not spread to the liver or other organs, and as long as it is not a recurrent cancer (already previously treated). As long as proper treatment is applied while the disease is localized in the colon or rectum, there is an almost 90 percent chance the patient will still be alive in five years. This percentage goes down to 70 percent if proper treatment is applied when the disease has spread to the surrounding lymph nodes.
In cases where the cancer has spread to other organs, only 13 percent are expected to be alive in five years, despite receiving proper treatment. This is the reason why there is a continuous search for better and better treatment which will allow patients with colorectal cancer to live longer lives free from the signs and symptoms of the disease.
Standard medical treatments
Systemic or drug treatment for cancer given in the form of pills or by injecting into the blood stream is also knowm as chemotherapy. Chemotherapy works by recognizing cells undergoing growth and multiplication or those that are rapidly dividing and then killing these cells.
Unfortunately, many normal cells of the body are constantly rapidly dividing and these too are killed by chemotherapy. Hair roots, for example, are rapidly dividing; hence some chemotherapeutic agents cause hair loss.
The lining of the mouth to the stomach are also rapidly dividing and chemotherapy can cause mouth sores and nause and vomiting. The bone marrow cells are likewise rapidly dividing, explaining the lowering of the red and white cells of a patient undergoing this drug treatment, and also explaining why the immune system functions poorly when a patient has cnacer and is undergoing drug treatment.
There are molecules found on some colorectal cancers which have an important role in the propagation of the disease. They are targets of drug treatments because when exposed to these drugs, the cancer cell dies instead of growing bigger.
One such class of targets is called the epidermal growth factor receptor (EGFR). EGFR which belong to the ras pathway have K-ras and N-ras molecules which, when they are seen in their natural state and are not mutated, are recognized and targeted by drugs called EGFR inhibitors.
These medicines, for example, cetuximab and panitumumab, are not chemotherapy but rather are called biologic or targeted treatment for cancer. Another term for these medicines ending in “-mab” are monoclonal antibodies. These monoclonal antibodies work best together with chemotherapy and can extend or even save lives of colorectal cancer patients, even when already in the advanced stage.
Another target in the biologic treatment of colorectal cancer is the Vascular Endothelial Growth Factor Receptor (VEGFR). This class of biologic treatment of cancer are the anti-VEGFR therapies. Regorafenib is an example of an anti-VEGFR drug. The “-nib” denotes that it is a tyrosine kinase inhibitor (TKI), and not a monoclonal antibody. As a general rule TKIs are smaller molecules and can be absorbed in the stomach and so are in tablet form (monoclonal antibodies are larger and have to be given through the veins). Also as a general rule, TKIs can work on its own, without partnering with chemotherapy treatment.
“Monoclonal antibodies work best together with chemotherapy and can extend or even save lives of colorectal cancer patients, even when already in the advanced stage”
The future of cancer treatment
The treatment of colorectal cancer with chemotherapy will continue over the next few decades. The improvement in survival rates, however, will likely come from newer targeted treatments to be used together with chemotherapy.
Harnessing the immune system will also come into play via the creation of personalized vaccines unique to the patient’s very own cancer. This, together with better screening and prevention methods, will lessen the number of people afflicted with this disease, and someday soon hopefully get rid of the disease or at least allow a people afflicted with it to live longer lives with better quality.
February 2015 Health and Lifestyle