Genetic Counseling and Testing

Cancer Genetic Testing

  • Genetic testing can be used to determine if someone has a change in their genes (mutation) that make them more likely to develop certain diseases such as cancer.
  • Genes (mutation) that make patients more likely to develop certain diseases such as cáncer of breast, ovarian, colon, thyroid, lymphoma or any other cáncer including pancreatic cancer, and melanoma.
  • Genetic testing can help women diagnosed with breast cancer make surgical decisions such as whether to undergo lumpectomy, neoadjuvant chemotherapy, radiation, breast-conserving surgery or bilateral mastectomy.

You’ve probably heard about testing for the BRCA1 and BRCA2 gene mutations, which can pass through families and increase the risk of breast cancer, ovarian cancer, and other types of cancer. Most people who develop Cancer have no family history of the disease. However, when a strong family history of breast and/or ovarian, colon, thyroid, lymphoma or any other cancer is present, there may be a reason to believe that a person has inherited an abnormal gene linked to higher cancer risk. Some people choose to undergo genetic testing to find out. A genetic test involves giving a blood, cheek swab or saliva sample that can be analyzed to pick up any abnormalities in these genes. Genetic testing identifies changes in chromosomes, genes, or proteins. In summary, genetic testing can be used to determine if someone has a change in their genes (mutation) that make them more likely to develop certain diseases such as cáncer.

An alternative and commonly used genetic testing involve direct tumor testing when a tissue sample is removed. The DNA or protein markers in the tumor are studied to determine if different treatments may be better or worse for you.

A gene is the basic physical and functional unit of heredity. It is a portion of a chromosomal DNA molecule that serves and controls the development of one or more traits and is the basic unit by which genetic information is passed from parent to offspring.  Genes control the characteristics that an offspring will have by transmitting information in the sequence of nucleotides on short sections of DNA.

The word “mutation” refers to a variation in the DNA that disrupts the function of a gene. Sometimes the word “abnormality” is used instead of “mutation.”

Changes in our genes, like mutations, can cause medical problems. Some medical problems are hereditary, meaning they are caused by a gene mutation (or mutations) that are inherited (or passed on) from a parent. Sometimes, a mutation might occur for the first time in someone, and be passed on to their children.

Every person’s genetic risk is unique. An oncologist or genetic counselor can help you decide which genetic test is right for you. Commercial kits have many issues in reliability and the problem surmounts in finding the accurate interpretation of the test

Genetic testing involves taking a sample of blood, cheek swab, or tissue in order to analyze a person’s genes. Genetic testing can be used to determine if someone has a change in their genes (mutation) that make them more likely to develop certain diseases such as cancer.

Three of the most well-known genes that can mutate and raise the risk of breast and/or ovarian cancer are BRCA1BRCA2, and PALB2. Women who inherit a mutation, or abnormal change, in any of these genes — from their mothers or their fathers — have a much higher-than-average risk of developing breast cancer and/or ovarian cancer. (Abnormal PALB2 genes are suspected to raise the risk of ovarian cancer, but larger studies need to confirm that risk.) Men with these mutations have an increased risk of breast cancer, especially if the BRCA2 gene is affected, and possibly of prostate cancer. Many inherited cases of breast cancer have been associated with mutations in these three genes. These genes can also increase te risk for other cancers, including pancreatic cancer, and melanoma. Other gene mutations have been discovered that increase the risk for these cancers including “PALB2,” “CHEK2,” “ATM,” “BRIP1” and others.

 

What are the benefits of genetic testing?

Genetic aberrations impact cancer prognosis and treatment decisions. Genetic testing for certain gene mutations associated with hereditary cancer can provide relevant medical information for the person undergoing the testing and for his or her blood relatives; but also in the medical-decision process most beneficial for the patient. Knowing if you have an inherited risk for cancer can be a useful tool to guide prevention and risk-reduction. If you have an elevated risk of developing cancer-based on your genetic test result, you can work with your oncologist provider to create a plan designed to prevent cancer entirely or help to identify cancer at its earliest, most treatable stage.

Benefits and role of genetic testing for people already diagnosed with cancer include:

  • provide an explanation for your personal or family history of cancer
  • evaluate your risk of developing future cancers
  • make informed medical decisions, including treatment for already-diagnosed cancer and/or surveillance and preventive options to help detect or prevent future cancers
  • It can help women diagnosed with breast cancer make surgical decisions such as whether to undergo lumpectomy, neoadjuvant chemotherapy, radiation, breast-conserving surgery or bilateral mastectomy.
  • It can help women diagnosed with breast cancer make surgical decisions such as whether to undergo lumpectomy and radiation or bilateral mastectomy.
  • It can help people diagnosed with metastatic breast cancer or advanced ovarian cancer make decisions about Immunotherapy with new checkpoint inhibitors.
  • It can help men diagnosed with prostate cáncer make treatment decisions.
  • It can help people diagnosed with cancer qualify for clinical trials enrolling people with hereditary cancer.
  • It can help people already diagnosed with cancer understand their risk for other cancers.
  • It can help family members who have not had cancer better understand their risk for cáncer and  identify other at-risk relatives for whom genetic testing is recommended

What are the point considerations and benefits of genetic testing for people who have not been diagnosed with cancer?

  • Testing negative may mean that the person did not inherit a mutation and they do not have an elevated risk for cancer.
  • It can help people better understand and manage their cancer risk.

Like any other medical laboratory texting, genetic testing has its limitations, Especially its uncertainty in providing in some cases a NO or YES  about hereditary cáncer risk. Another limitation is, that is very expensive when is not covered by insurance.

 

Some of the most common Genetic tests include:

Role of genetics in the diagnosis of breast cáncer.

A genetic variation in BRCA1 or BRCA2 can increase the likelihood that a person will develop cancer in his or her lifetime. Many other genes can increase an individual’s risk of developing breast cancer, including CDH1, PALB2, PTEN, STK11, and TP53. Like BRCA1 and BRCA2, many of these genes also influence risk for other types of cancers. Women with faulty BRCA1 and 2 genes might be candidates for the potential benefits of PARP inhibitor treatments. PARP is a key player in a cell’s DNA repair machinery. Its normal role is to repair tiny nicks in the DNA helix –the little snags and tears that occur during the day-to-day life of a cell. Although a little DNA damage is a bad thing – it can lead to cancer – a lot of it triggers another defense mechanism – cell suicide(apoptosis).

Genes commonly tested include:

 

 

Genetic testing may be appropriate if you have:

  • breast cancer diagnosed before age 50
  • ovarian cancer at any age
  • male breast cancer at any age
  • bilateral breast cancer or two separate breast cancer diagnoses
  • triple-negative (ER/PR/HER2-neu negative) breast cancer
  • both breast and ovarian cancer in close relatives
  • breast cancer in two or more close relatives on the same side of your family
  • a close blood relative with cancer in both breasts
  • a known familial genetic variant in a breast cancer susceptibility gene
  • Ashkenazi Jewish heritage with a family history of breast cancer
  • a clustering of cancers that may suggest an inherited cancer syndrome, such as breast cancer, thyroid cancer, pancreatic cancer, prostate cancer, bone or soft tissue cancer, sarcoma, adrenocortical carcinoma, or leukemia/lymphoma—all on the same side of your family

 

Role of genetics in the diagnosis of colorectal cancer.

 Genes commonly tested include:

 

  Genetic testing may be appropriate if you have:

  • colorectal cancer diagnosed before age 50
  • more than one type of cancer, including colorectal cancer
  • a high number (10 to 1000 or more) of precancerous colorectal polyps
  • 3 or more individuals on the same side of your family with cancers that may suggest an inherited cancer syndrome, such as colon, rectal, stomach, thyroid, uterine, ovarian, or pancreatic cancer

 

Role of genetics in the diagnosis of ovarian cancer.

Genetic testing of the BRCA1 and BRCA2 genes appropriate for any woman with a personal history of ovarian, fallopian tube, or primary peritoneal (the membrane that lines the abdominal and pelvic cavities) cancer. While most women develop ovarian cancer due to a combination of age, environment, lifestyle, and hormonal factors, it is estimated that about 15% of ovarian cancer patients are born with a gene mutation that increases their chances of getting ovarian cancer.

A study published in 2011 looked at 360 women newly diagnosed with ovarian, fallopian tube, or primary peritoneal cancer. Eighteen percent of women tested carried a mutation in the BRCA genes, and six percent carried mutations in other genes, such as TP53, RAD51C, RAD50, PALB2, NBN, MSH6, MRE11A, CHEK2, BRIP1, and BARD1. Thirty percent of positive women had no other family history of breast or ovarian cancer and over 35% were diagnosed after age 65.

Gynecologic cancers include those of the ovary and uterus. About 1.3% of women will develop ovarian cancer and 2.7% will develop uterine cancer. Most cases of gynecologic cancers are sporadic and not inherited; however, approximately 5%-10% of gynecologic cancers are inherited.

Variants in two genes, BRCA1 and BRCA2, account for the majority of hereditary ovarian cancer cases in women with a strong family history or an early-onset diagnosis. These variants can increase your lifetime risk by up to 54%. Lynch syndrome is the most common inherited cause of uterine cancer.

A genetic variation in BRCA1 or BRCA2 and/or Lynch syndrome genes can increase the likelihood that a person will develop not just gynecologic cancer, but also several other types of cancer in his or her lifetime.

Genes commonly tested include:

BRCA Genes

  • TP53
  • RAD51
  • RAD50,
  • PALB2
  • NBN
  • MSH6
  • MRE11A
  • CHEK2

 

Role of genetics in diagnosis & treatment of prostate cancer.

Certain men with prostate cancer and a family history of cancer are more likely to have a genetic mutation that may increase the risk of cancer for themselves and their families. Genetic testing might help such men make better treatment decisions.

Men with faulty BRCA1 and 2 genes are at higher risk of developing an aggressive form of prostate cancer. There are ongoing clinical studies to find out if screening could spot early signs of disease in this high-risk group and looking at the potential benefits of PARP inhibitor treatments.

PARP is a key player in a cell’s DNA repair machinery (we’ll look at some others later). Its normal role is to repair tiny nicks in the DNA helix –the little snags and tears that occur during the day-to-day life of a cell. Although a little DNA damage is a bad thing – it can lead to cancer – a lot of it triggers another defense mechanism – cell suicide(apoptosis).

 

Your oncologist or genetic counselor is the most qualify professionals to advise you on the types of genetic testing that you or your relatives need to identify any cáncer risk

 

Sources:

  • American Cancer Society
  • The National Cancer Institute
  • National Comprehensive Cancer Network
  • American Academy of Gastroenterology
  • National Institute of Health
  • MD Anderson Cancer Center
  • Memorial Sloan Kettering Cancer Center
  • American Academy of Hematology

 

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