Related information:  Precision Medicine | Preconception Genetic Testing | Targeted Therapy for Cancers

 

In Precision Medicine, the role of the doctor, in addition to the treatment of diseases, is to help prevent disease recurrence as well. For instance, many people may be unaware that some cancers can be genetically inherited, and we are now able to screen for cancer genes in Thailand. The Next Generation Sequencing Technology has the ability to sequence up to 95% of an entire human genome and conduct genetic mapping of families, whereby up to 50 of the most common cancer genes can be detected, including the 3 most common cancers in men and women.

The most common cancers in men are:

  1. Prostate Cancer
  2. Lung Cancer
  3. Colon Cancer

The most common cancers in women are:

  1. Breast Cancer
  2. Lung Cancer
  3. Colon Cancer

The human body is composed of trillions of cells with a wide variety of functions. Inside each of these cells is a nucleus (the command center), and within the nucleus, there are 23 pairs of chromosomes. Each chromosome contains a double helix of genetic material (DNA). Unique segments of the DNA are known as genes, which store genetic information and control cell division and activity.

We can compare genetic code to a book. Each person has their own personal book in which there are 23 chapters (23 chromosomes). Chapter 1 could be the first chromosome pair that controls eye color or hair color; chapter 2 controls bone strength; chapter 3 controls the growth of cancer cells and so on. This means that even if we have 99.9 % similarities, we have differences that are even more detailed than that. This is because although half the content of this book comes from our father and the other half come from our mother, oftentimes errors can occur during DNA replication or from other types of damage, and these mutations can cause cell proteins to malfunction or be missing entirely. When this happens, it can disrupt normal development or cause a medical condition. This kind of condition is called a genetic disorder.

Gene mutations occurs in 2 major ways:

  1. Germline mutations or inherited mutations refer to abnormalities or mutations in a gene that are present in the body cells from birth and are then passed on to the next generation
  2. Acquired mutations are genetic mutations caused by environmental factors, such as toxins in the environment, x-rays, smoking, or from errors made during replication when the DNA copies itself to prepare for cell division (mitosis). Every time a cell divides, it is another opportunity for mutations to occur, and thus gene mutations build up over time, usually appearing as disorders when a person is older. These kinds of mutations cannot be passed to the next generation.

There are about 500 genes involved in cancer out of the over 20,000 genes in the human body. These can be divided into 2 major categories, as follows:

  1. Oncogenes: Genes that stimulate uncontrolled cell growth and division.
  2. Tumor suppressor genes: Normal genes that repair DNA mistakes and slow down cell division.

Testing for specific inherited changes in a person’s genes is carried out for the purpose of prevention and to help assess the risk of cancer in the future. It is suitable for people who have a family history of cancer and for cancer patients who want to know the true cause of the disease, which will also benefit other members in their family. At present, genetic testing can be performed from a blood sample without the patient needing to forgo food or drink before the test, and results are available in just 4 weeks.

If you are found to be at risk, your doctor can help you with treatment and lifestyle planning for the future. For example,

  • You may be advised to undergo screening sooner than would otherwise be recommended with imaging tools such as MRI, mammogram, colonoscopy.
  • For safe medication selection, you maybe suggested dietary adjustments and better lifestyle choices that can help to reduce risk.
  • Your information can be used to notify and provide necessary assistance to other family members who may also be at risk in the same way as you are.

If, when you undergo testing, and no risks are found, this unfortunately does not mean you have no chance of cancer in the future, as this type of testing only tests for inherited risks, which currently represents 10% all cancer risks. The other 90% is made up of environmental risks and lifestyle factors that adversely affect one’s health, and these we must all fight to look out for and prevent.


1. Patients with family members who have died from cancer
2. Patients whose annual health check detected no abnormalities, but are experiencing signs of chronic fatigue, weight loss, flatulence, indigestion, abdominal pain, alternating constipation and chronic diarrhea, bloody or tarry stools, difficulty urinating or blood in urine, yellow or bloody discharge from the nipples, enlarged armpit lymph nodes, new growths or enlargement of black-colored lumps or nodules similar in appearance to a mole or other signs or symptoms.
3. Patients in high-cancer risk environments, such as, people who live or work in or near agricultural areas that use pesticides, areas with heavy traffic or various types of industrial factories, or those with lifestyle-related cancer risk factors, including chronic stress; smoking; intense exposure to the sun; frequent consumption of roasted, fried or grilled, preserved, partially cooked or raw foods; and regular consumption of processed meat products, such as sausages, ham and bacon.

How is Preliminary Risk Assessment Carried Out?

 

Have you ever wondered what the chances are that you have inherited cancer genes from your family?

  • More than 2 close relatives—parents, siblings, direct blood relatives—on the same side of your family (either your father or your mother’s relatives) have passed away from cancer.
  • Those relatives have had the same type of cancer, or different types of cancers that can be caused by the same gene fault.
  • Those relatives passed away from cancer at a relatively young age—below the age of 50.
  • One of your relatives has had a gene fault found by genetic testing.

Generally speaking, cancer is most common in people over the age of 60. If it is found at a young age, it could likely be due to inherited cancer-causing genes.

1. Environmental risk factors such as carcinogenic substances in food and beverages, air pollution, radiation exposure, certain viruses, bacteria and parasites.

2. Behavioral risk factors such as smoking, regular consumption of alcohol, foods that are high in fat, very salty or sweet foods, preserved foods, foods containing preservatives and burnt foods.

3. Genetic risk factors such as abnormal genes inherited from the father or mother.
Some simple principles for cancer prevention are: exercise regularly, stay positive, make sure at least half your meal content is fruit and vegetables, eat a variety of foods, avoid unhealthy foods, and, very importantly, have annual health checkups in order to spot cancer cells early on as well as to detect any latent cancer genes we may have inherited. Nowadays it is possible for doctors to treat and cure many different types of cancer and provide cancer patients with much longer lives and higher survival rates, depending on the type and stage of cancer that is detected. However, as always, prevention is better than cure. Avoiding the risk factors mentioned above, leading a healthy lifestyle, and undergoing regular check-ups and screening are the keys to beating cancer.


Forty years ago, locating the abnormalities of each individual gene on a single strand of DNA was a slow process, requiring almost a week to sequence each gene. Using this older sequencing method, known as Sanger Sequencing, meant that sequencing the more than 20,000 genes contained in the human genome was a difficult and lengthy process that could take almost a year.

Today, medical science has developed a technology known as Next Generation Sequencing, which enables the detection of gene mutations in every gene contained in the DNA of every living organism. This means expedited identification and delivery of genetic results (results can be made available within a month), much easier and more widespread access, and up to 90% accuracy in the detection of various diseases, whether latent cancer-causing genes, recurrent genetic diseases in families, or other mutations found in human DNA.

Medical technology today has adopted Next Generation Sequencing for a number of important applications, such as:

  • Hot Spots or Panel Sequencing: For targeted analysis of specific regions of the genome or key genes in an area of concern known to be a mutational hotspot, or to find a select set of genes with known associations to a particular disease or phenotype. For example, it can help to find genetic disorders or genetic diseases, including cancer, both inherited and non-inherited, and can help in selecting the appropriate cancer medication and treatment for each individual patient.
  • Whole Exome Sequencing or Targeted Region Sequencing: Sequencing of all exons in a person’s DNA in order to identify any possible disease-causing mutations that is of interest to the doctor. (Additional explanation: Exons are parts of the DNA which can be called base sequences or segments that occur along the length of the gene. Exons are important because they are able to be transcribed or translated. Exons are separated by intervening sections of DNA known as Introns, which are not integral in the transcription or translation of the genetic code.)
  • Whole Genome Sequencing: Decoding the whole DNA product to unlock the genetic secrets of an entire genome of both intron and exon mutations. This technology covers diseases in over 95% of an entire human genome, as well as enables the prediction of human chromosome structures and contributes to unlocking the secrets of science in the future.

Related information:  Precision Medicine | Preconception Genetic Testing | Targeted Therapy for Cancers


Our Doctor

Objoon Trachoo, M.D.

Medical Education
Ph.D. Biomedical Science,
University of Sheffield,
United Kingdom 2010.

 

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