Physicians of the Zane Cohen Centre

What are the cancer screening guidelines for LS?

Colorectal Cancer Screening

• Colonoscopy every 1-2 years beginning at age 20-25

• Some families may be advised to start screening at an earlier age.

  *Evidence shows that regular colonoscopy reduces the risk of developing colorectal cancer in LS patients.

Gynecological Cancer Screening

• Annual trans-vaginal and pelvic ultrasound

• Annual CA125 blood test

• Be aware of signs and symptoms of endometrial cancer such as irregular or heavy vaginal bleeding and prompt evaluation if any of these symptoms occurs.

• Prophylactic hysterectomy and bilateral salpingo-oophorectomy (removal of uterus, fallopian tubes and ovaries) may be considered when child-bearing is completed.

*The effectiveness of screening for endometrial and ovarian cancer is limited and its value has yet to be established.

Other LS-related Cancer Screening

Individuals with LS are at increased risk of developing other types of cancer. At this time, routine screening of other organs has not been shown to be effective. Based on family history of non-colorectal or non-gynecological cancer, other screening procedures may be recommended.

Some families with LS may develop specific skin lesions called keratoacanthomas or sebaceous adenomas which occasionally lead to sebaceous carcinomas. Any unusual skin findings should be reported to a physician.

Individuals with LS are encouraged to discuss all changes in general health with their physician.

Please note: Screening recommendations must be given by a genetics specialist and/or physician after a complete assessment of a family. Please talk to your physician if you have questions or concerns about screening recommendations for you.

What causes LS?

LS is a hereditary condition. This means that it can be passed down from parent to child through our genes. Each cell in our body carries thousands of genes that tell our bodies how to grow, develop and function properly. LS is a condition caused by a change in a gene; this is called a mutation. Mutations cause our genes not to work correctly and this can lead to certain diseases such as LS.

Everyone has two copies of every gene (including the LS genes); one copy was inherited from their father and one copy from their mother. For families with LS, the children and siblings of someone with LS have a 50% (1 in 2) chance of inheriting that same LS mutation.

It is not actually the cancer that is inherited, but rather the increased risk of developing cancer that is inherited. The gene mutation increases a person's chance of developing cancer but does not mean that they will definitely develop cancer.

How does genetic testing for LS work?

A person referred to a genetics clinic will be asked to provide family history information so that a family tree can be developed. This helps us determine if the family history looks like sporadic CRC or LS.

Patients may be asked to sign medical release forms that would allow to access medical records pertaining to a cancer diagnosis. Similar forms may be provided for the patient to share with relatives (or their next of kin) who have had cancer.

If a family is suspected of having LS, genetic testing may be offered. The first step in testing for LS is to look at tumor samples. The majority of tumors that are associated with LS show particular characteristics called microsatellite instability. The tumors may also show the loss of the normal product of a LS gene (called immunodeficiency). If these characteristics are seen in a tumor then we move on to the second step.

The second step is genetic testing of a blood sample. There are four genes (MLH1, MSH2, MSH6 and PMS2) that are known to be associated with LS. Genetic testing looks for a mutation in one of these genes. If a mutation is identified in a family, other relatives in that family can be tested to see if they inherited the gene mutation.

Sometimes the testing process does not identify a mutation in a family. In these cases we may not be able to confirm or rule out a hereditary cancer syndrome.

The decision to have genetic testing involves a careful consideration of the potential impact of the results. If an individual is eligible for genetic testing, they must receive genetic counseling prior to testing to learn about the benefits, risks, and limitations of genetic testing.

Who is at risk for LS?

All individuals have a chance of developing cancer throughout their lifetime. Colorectal cancer (CRC) refers to cancer that starts in either the colon or the rectum. CRC is very common in Canada. The chance of developing colorectal cancer in the general population is about 1 in 16, or 6%. The average age of diagnosis of CRC in Canada is approximately 65 years.

As we age, the cells that line the colon and rectum are damaged by environmental factors, such as diet and as a normal part of the aging process. Over a lifetime this damage accumulates and can lead to colorectal cancer. This is thought to explain the majority of cases of CRC, which we call sporadic.

We see differences between families with sporadic cases of CRC and families with LS. LS families often have multiple individuals with CRC and other LS-related cancers (i.e. endometrial cancer), several generations with these cancers and the cancers are often diagnosed at younger ages (typically under age 50).