Colorectal cancer is the growth of cancer in parts of the large intestine, specifically the colon and rectum. It can be difficult to detect colorectal cancer early because it is not associated with specific tell-tale symptoms.
Instead, patients may present with non-specific symptoms like constipation, diarrhoea, abdominal discomfort, weight loss and blood in the stool. Other patients may not experience symptoms at all.
Based on Malaysian data gathered in 2012, colorectal cancer ranks as the most common cancer diagnosed in men, and the second most common cancer in women. While colorectal cancer is historically associated with more developed countries, the numbers are rising rapidly in the developing world, including Malaysia.
Treatment of colorectal cancer is customised to the patient, based on factors like cancer stage, genetic mutations present in the cancer, and patient’s age and general health status. In its early stages, colorectal cancer is highly curable, with rates up to 90% in certain groups of patients.
For stage 1 cancer, surgery alone is sufficient to cure the disease. In stages 2 and 3, patients may undergo chemotherapy and radiotherapy following surgery to reduce the risk that the cancer may recur and spread, and to improve the chances of survival.
However, most Malaysian patients are diagnosed in stage 4, where the cancer has already spread or metastasised. At this stage, the aim of treatment is to extend life for as long as possible without affecting patients’ lifestyles.
Chemotherapy is the backbone of metastatic treatment. FOLFOX and FOLFIRI are among the chemotherapy combinations with the strongest evidence for effectiveness, measured as tumour response (halting or reversing growth) and improved life expectancy.
Medical breakthroughs have identified biological features that predict tumour behaviour and genetic mutations that accelerate cancer growth. These discoveries have led to new medications that target these genetic mutations.
These medications, such as anti-vascular endothelial growth factor (VEGF) and anti-epidermal growth factor receptor (EGFR), further extend patients’ life expectancies.
Depending on a patient’s disease characteristics, general health and socioeconomic factors, among others, the 2016 guidelines developed by the European Society for Medical Oncologists (ESMO) suggested that a patient can expect to live up to 30 months with access to appropriate treatment.
The standards of European healthcare services may be challenging to replicate in this region, but Asian medical associations are promoting ESMO principles, having recognised that they provide the best possible treatment strategies.
The guideline recommends that a newly-diagnosed patient should be prescribed with the therapies stated above, and one of them includes an anti-VEGF drug that disrupts the blood supply to tumours, slow their growth and extends their lifespan.
As anti-VEGFs were not developed to target a specific mutation, they may be prescribed in most patients with metastatic colorectal cancer.
A combination of chemotherapy and an anti-VEGF may also be prescribed, depending on the patient’s condition, to maintain control of the cancer after the first course of treatment (maintenance therapy), and to treat recurring cancers (second-line therapy).
Maintenance therapy with an anti-VEGF in particular, is important to delay further tumour growth.
Patients who test positive for RAS wild-type, a subtype of colorectal cancer, have activated RAS genes that promote tumour cell growth and survival. In these patients, prescribing an anti-VEGF drug or an EGFR antibody, with chemotherapy, would improve treatment effectiveness.
Treating metastatic colorectal cancer is challenging. Patients should always make it a priority to discuss treatment goals and options with their doctors during their regular appointments, so that they remain adequately informed and in control of their health.