About Authors: With over 20 years of experience in the field of medicine, Dr Sudhir Borgonha, Chief Medical Officer, Strand Life Sciences leads the targeted therapy business for Strand Life Sciences, since 2015. In a career spanning over 12 years, mostly in high volume centres all across the country, Dr Shabnam Bashir, Associate Consultant Oncosurgery, Apollo Hospitals has performed a large number of varied open and laparoscopic procedures.
Colorectal cancer encompasses both cancers of the colon and the rectum. According to the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC), it is the second most common cancer worldwide after lung cancer. Colon cancer and rectal cancers are often grouped together due to similarities in their invasiveness.
Functionally, the colon reabsorbs large quantities of water and nutrients from undigested food products as they pass through it. The rectum is the end of the colon and stores the waste material of the digested food before being expelled from the body.
In general, most colorectal cancers begin as a form of polyp – that is a kind of growth on the inner lining of the colon or the rectum. Some of these polyps can become cancerous over a period of years. However, it must be noted that not all polyp-like growths are cancerous in nature. The chance of these polyps becoming cancerous depends largely upon the kind of the polyp. Doctors can distinguish between different types of polyps and have found that the kind known as adenomatous polyp has the highest tendency to develop into cancerous polyps.
The usual symptoms of colorectal cancer are diarrhea, constipation, blood in the stool, abdominal pain and bloating issues, fatigue and unexplained iron deficiency in men.
A look at colorectal cancer risk factors
There are several factors which can increase the risk of an individual for colorectal cancer. There are several lifestyle-related factors that have been linked to an increased chance of getting colorectal cancer such as being overweight or obese, lack of physical activity, certain types of diets, especially if they include highly processed meat, smoking and alcohol use
In addition, there are certain medical conditions which can predispose an individual to develop colorectal cancer. These are as follows –
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A personal history of inflammatory bowel diseases
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A family history of colorectal cancer or adenomatous polyps
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Having an inherited syndrome, like Lynch Syndrome for example.
Challenges in colon cancer diagnosis and management
Science and medicine have made rapid advancements in the area of colorectal cancer detection and treatment. Today, colorectal cancers are very much treatable and most of the patients have been known to lead a very normal life after it has been treated. However, at the same time, disease monitoring for such patients is a huge challenge. Carcinoembryonic antigen (CEA) is a routinely used biomarker for the surveillance in colorectal cancer patients which has been shown to be at elevated levels in the event of colorectal cancer. However, it has proved to be not a very reliable marker. Early detection is the basics of cancer research and any effort to increase detection of cancer at an early stage should be welcome.
In recent years, a blood-based liquid biopsy approach for monitoring colorectal cancer has emerged and is about to enter the clinic. Using a liquid biopsy approach, the pathology lab can extract tumor DNA from a blood sample, which can be used for monitoring the disease progression.
Healthy individuals shed very low levels of circulating nucleic acids in their blood due to constant tissue renewal. This delicate balance is thrown off when a person has developed cancer and the amount of DNA that finds its way into the blood stream increases significantly, enough to be detectable by the latest laboratory and analysis techniques.
Liquid biopsies are used to detect such circulating tumour cells and cDNAs screen (non-invasively) for early-stage cancers, to monitor responses to treatment especially in stage 4 cancers, as well as help explain why some cancers are resistant to certain therapies as they give us a real time evaluation of molecular biology. Therefore, this approach has become a promising new method for monitoring therapy response, disease progression and even relapse long before any other screening method would be able to detect that the cancer has relapsed.
Colon Cancer Genetics
With rising cancer incidences in India, including many colorectal cancers, it is crucial to continue to develop newer ways and methods to detect colorectal cancer early on, when treatment is more straightforward and more likely to be successful. Recent advances in genetics have allowed us to get an unprecedented glimpse of tumor biology and the genetic mutations that drive colorectal (and other) cancers. The gene mutations that are most significant for detecting colorectal cancer due to how frequently they occur (Jauhri, M et al, 2017) are:
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KRAS- 35.7%
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BRAF- 7.1%
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PIK3CA- 16.1%
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NRAS- 6.3%
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TP53- 39.3%
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APC-29.5%
