Cancer

Cancer is a collective term for a number of diseases with common characteristics. All cells in our body have an “internal clock” that controls the different phases of the cell cycle, i.e. the stages that take place in the cell during its growth, cell division and/or cell death (apoptosis). In cancer cells, this regulatory mechanism (“internal clock”) is altered.

The onset and development of cancer is a complex process that has a multifactorial origin. Among the causes related to cancer are genetic and environmental factors. These factors alter the genetic material (DNA) of cells, leading to dysregulation of the “internal clock” and uncontrolled proliferation.

Some of the factors that promote these changes and play a role in the development of cancer are:

• The natural ageing process
• Lifestyle (unbalanced diet, insufficient exercise, smoking, alcohol consumption…)
• Certain external influences (viruses, pollutants, UV radiation, etc.)
• Hereditary or genetic factors

To summarise, the main stages of the different types of cancer are as follows:

• Uncontrolled multiplication (proliferation) of normal cells that turn into cancer cells (tumour cells).
• Invasion of the surrounding tissue by cancer cells, causing displacement and destruction of the surrounding tissue.
• Metastasis formation when some cancer cells move from their place of origin and form new tumours (metastases) in other parts of the body.

There are families in which certain types of cancer, especially breast cancer, ovarian cancer or intestinal cancer, are more frequent. However, this frequent occurrence does not automatically mean that there is a genetic predisposition to suffer from it.

Certain criteria and tests are used to determine whether a cancer is hereditary. If there is a suspicion, it is possible to receive genetic counselling or advice and, if appropriate, genetic testing which can identify whether there are certain mutations in the family that carry an increased risk of developing a type of cancer.

To summarise, a family is suspected of having one of these mutations if:

• Several members of different generations have developed the same type of cancer, usually at young ages (15-20 years earlier than the population average). For example, a mother and sister with breast cancer or a father and daughter with bowel cancer.
• The same person having suffered from several types of cancer.
• Ashkenazi (Eastern or Central European) Jewish ancestry and a family history of breast or ovarian cancer.
• Polyposis or multiple polyps in the stomach or intestines.

In the event that a person is a carrier of a genetic mutation that predisposes to a higher risk of suffering from some type of cancer, he or she can transmit this mutation with a 50% probability to his or her offspring. If a person has not inherited the mutation from their parents, their own children will not be affected as the mutation does not skip a generation.

Breast and ovarian cancer

• In five to ten percent of those affected, breast cancer develops as a result of an inherited predisposition (inherited mutations). In the case of ovarian cancer, the hereditary proportion is ten to twenty percent.
• If a predisposition exists, women have a higher risk of developing breast and ovarian cancer than those without. Men with such mutations have an increased risk of breast and prostate cancer. Both men and women may have an increased risk of pancreatic cancer or melanoma.
• Genes associated with an increased risk of breast or ovarian cancer: BRCA1, BRCA2, MLH1, MSH2, MSH6, PMS2, EPCAM, TP53, PTEN, STK11, CDH11, PALB, CHEK2, ATM, NBN, BARD1, BRIP1, RAD51C, RAD51D.

Prostate cancer

• About ten percent of prostate cancers are hereditary.
• The risk of developing prostate cancer is higher if a relative (father or brother) is affected by prostate cancer.
• Genes associated with an increased risk of prostate cancer: BRCA1, BRCA2, MLH1, MSH2, MSH6, PMS2, EPCAM, TP53, CHEK2, ATM, NBN.

Colon or rectal cancer

• About 5% of cases are hereditary.
• Other cancers are also more common in families affected by colon cancer than in the average population. These include cancers of the endometrium, stomach, small intestine, kidneys, ureter, bile ducts, pancreas and ovaries.
• Genes associated with an increased risk of colorectal cancer: MLH1, MSH2, MSH6, PMS2, EPCAM, TP53, PTEN, STK11, BMPR1A, SMAD4, GREM1, POLD1, POLE, CHEK2.

• Single gene analysis: Analysis of a single gene associated with an increased risk of developing the type of cancer in question.
• Gene panels: Complete sequencing of several genes associated with an increased risk of the type of cancer in question to determine if the person is a carrier of one of the mutations. This test uses massive sequencing technology or NGS (next generation sequencing).
• Exome
• Genome

It is important to understand that what is inherited is the risk, the susceptibility to suffer a certain type of cancer. In other words, not all people who have inherited one of these mutations will develop the disease, but the probability that they will end up suffering from cancer will be greater than the probability of the general population. Only some people with a genetic mutation will develop cancer.

If the test result is negative, there is no proven genetic risk of developing cancer. However, this does not mean that you cannot develop cancer during your lifetime.

In other words, a woman can have a 45% to 65% chance of developing breast cancer and never develop the disease. While a woman with a 25% chance can develop breast cancer.

Genetic counselling can help determine whether cases of cancer in the same family have a common genetic origin and, if so, communicate to family members the risk of developing cancer at some point in their lives.

To do this, the genetic counselor:

• Reviews your personal and family history of cancer
• Creates a family tree (pedigree)
• Provides a personalized cancer risk assessment
• Discusses whether genetic testing is recommended

He/she will also inform high-risk patients about preventive measures:

• Lifestyle (diet, physical exercise…)
• Intensive screening programs including examinations staggered according to age (palpation, ultrasound, mammography, endoscopy and other imaging procedures)

The genetic counselor will take into account and inform the patient about the possible social and economic consequences, as well as the psychological burden. He/she will give him/her all the necessary information to be able to reflect, also within the family circle, on the consequences of the results of the genetic study.