Inherited cancer syndromes have been in the news lately, brought to the fore with recent announcements by Angelina Jolie. In addition to the preventative double-mastectomy that she had a few years back, she has now also had her reproductive organs removed. Jolie has BRCA, a genetic mutation that predisposes the people who carry it to breast and reproductive cancers—at rates high enough that many would say malignancies are virtually inevitable without the steps that Jolie is taking(1).
Lynch syndrome is like BRCA, and credible sources estimate that its rate of occurrence is at least as high if not higher than BRCA. It simply does not get the same press, primarily because there are no high profile spokespersons talking about it.
While Lynch syndrome is not common, it certainly is not rare. Enough people worldwide are afflicted that it does not bear that designation: in the USA, the occurrence rate needs to be less than one in 2000 people for a condition to be considered rare(2). It’s estimated that one in 400 people have Lynch syndrome(3); unfortunately, however, only about 5-10% of those people have actually been diagnosed(4).
But what is this syndrome, why is it worthy of notice, and why is it important that those people who have it are identified?
Watch Out! Here Be Science!
Lynch syndrome is a collection of autosomal dominant gene mutations which are identified by the lack of one or more of a set of proteins in a carrier’s DNA. These proteins are called mismatch repair genes (MMRs), and their lack means that a carrier’s body has a harder time fixing the errors that frequently occur when cells, and their DNA, divide. Thus, while Lynch syndrome does not itself cause cancer, its MMR deficiency means that when errors in cell division occur, a body with Lynch has fewer means to fix or remove those errors, so that the mistakes more often become malignancies(5).
Yikes! That explanation contains a lot of scientific terms, so let’s break them down.
Lynch syndrome is a collection of mutations. Lynch doesn't refer to a single condition but is, rather, a convenient way to group together mutations on five different genes (more may yet be discovered) which all have the same primary effect: a high tendency to develop colon cancer. Most people who have Lynch syndrome have only one of the mutations—although it is possible to have more than one (and increased cancer rates into the bargain). These variants are called by the name of the specific gene or protein that is defective and have names like MLH1 and MSH2 (the two most common variants)(6).
While each mutated gene has its own special powers, they all have a couple of things in common. First, a tendency to high rates of cancers at an early age, and second, a tendency for the colon and uterus to be the primary places where these cancers manifest. Each Lynch mutation also has its own set of additional likely cancers which occur with varying rates of probability, but no matter the type of cancer involved, the statistical likelihood of its occurrence is much higher in Lynch carriers than in the general population(7).
Oh, and one more thing: Lynch mutations are also profoundly under-diagnosed. That is, many more people than the number who’ve been identified to date actually have the condition, and that is a problem(8). More on that later.
Lynch syndrome is an autosomal dominant mutation. A mutation is a deviation from the standard human genome—an individual difference that is permanent(9). If you have a mutation, you have it from birth, you have it in all your DNA, and it makes you special from a genetic standpoint. The fact that it is autosomal dominant means its effects are felt every time the mutation is passed on: Lynch is never recessive, and it can't skip generations(10). If a parent passes on the mutation, the child has the syndrome. There are no people who are carriers yet who experience no effects: the mutation always expresses itself as a lack of a certain protein, that being a protein which provides important protection against cancer.
However, there is good news as a result of this dominant characteristic: a carrier has no more than a 50% chance of passing on the mutation to his or her children. While genes come in pairs, the body’s reproductive cells (eggs or sperm) do not have the gene pairs that full DNA does. Rather, they have only one or other of the genes from each pair in DNA. The chance of the mutated gene, rather than the healthy gene, being in any one reproductive cell is 50%. Half of my sperm, then, have the MSH2 genetic mutation and half do not. Statistically speaking, any children I bear would each have a 50% chance of having Lynch syndrome. In reality, I have three children, and one of them has the mutation. This statistical probability holds up as I look back into my family tree. I can clearly see the effects of the mutation across generations in my mother’s family, discerning from the cancer incidence patterns who the historical carriers are and are not. As I trace the gene’s devastating effects in cancer occurrence, I see its presence in about 50% of my forebears.
Lynch syndrome is a deficiency in one or more mismatch repair proteins (MMR). These proteins are designed to fix problems which regularly occur when cells divide: DNA is a complicated thing, so errors can creep in when it gets duplicated. The job of MMR is to detect errors and then fix them(11). When the errors do not get fixed, they accumulate, eventually resulting in cells which group together, dividing out of control. This uncontrolled division results in tumours—what we refer to as cancer. The biochemical pathways of cancer development are still poorly understood, but a critical factor in Lynch syndrome is that one of the first lines of defence in stopping cancer is absent, thus making cancers appear early (usually before the age of 50), often (60-80% likely in Lynch carriers), and repeatedly (it is not unusual for Lynch carriers to get cancer more than once in their lifetime, more than one kind of cancer, and even different kinds of cancer at once)(12).
The Effects of Lynch Syndrome
People with Lynch syndrome are prone to a variety of cancers. The most prevalent kind is colon cancer, with an occurrence rate of 60-80% before the age of 50. In women who are Lynch carriers, endometrial (wall of the uterus) cancer has almost as high a rate of occurrence. Moreover, in addition to colon and endometrial tumours, a host of other cancers occur with increased incidence, the specific rate depending on the kind of cancer and the variant of Lynch. These include (but are not limited to): small intestine, stomach, esophagus, pancreas, bladder, lung, breast, bladder, skin, brain, and bile duct(13).
All of this is not to say that Lynch syndrome directly causes cancer, because it does not (unfortunately, there are hereditary conditions that do directly cause cancer). Rather, Lynch syndrome allows cancers to happen. So, not everyone who has Lynch will get cancer, despite the very high likelihood.
How Lynch Syndrome is Diagnosed
The gold standard for determining that someone has the mutation is a blood test where the DNA of the patient is examined to detect whether one (or more) of the MMR proteins is absent(14). If it is, the patient is diagnosed with Lynch syndrome. The genetic test can be performed at any point in a person’s lifetime but is generally not done until after a person reaches 18, in order to avoid the ethical problem of testing minors (with or without their express consent) and the psychological difficulty that youngsters may have in bearing such knowledge during their developmental years.
Genetic tests are not done routinely, however, for at least two reasons: these tests are expensive, and there is a lack of capacity in testing labs. They are done only when there is a high likelihood that a person has the mutation. This likelihood is assessed in a couple of ways: first, if a person already has a tumour, the tissue can be tested for certain characteristics to determine the probability of the patient having Lynch; second, if a person does not have cancer, the family tree can be examined to determine whether the occurrence and type of cancers in the family are indicators of an inherited mutation.
One of the prevailing problems with the Lynch testing protocols is that they are not well enough known in the medical community. You would think doctors would be well versed in a condition which affects one in 400 people—as common as HIV-AIDS, Parkinson’s, Crohn’s, and cerebral palsy, and about twice as common as Down syndrome and multiple sclerosis. Nonetheless, many doctors, even in Ivy League medical schools, do not know about Lynch, so too many family trees remain insufficiently examined to detect genetic conditions that may be present.
Moreover, even where knowledge of Lynch does exist, protocols are inconsistently applied. The testing protocols for tumour tissue (most often colon tumours) are not implemented in all jurisdictions in North America. In some places—like Manitoba, Canada, where I live—it is standard practice to test every colorectal tumour for the indicators of Lynch syndrome and to follow up with genetic counselling, DNA tests, and surveillance for patients whose tumours indicate Lynch(15). Follow-up then moves to the family members of Lynch-positive patients. In a neighbouring province, none of this happens.
Thus, you are your own best advocate when it comes to the first steps in determining whether you are at high risk of being a Lynch syndrome carrier. The steps are simple: look at your family tree to see if there has been a high occurrence of cancer (especially colorectal or uterine) in your direct relatives (parents, grandparents, siblings, children), and, if there has, whether those people got cancers at an unusually young age (getting colon cancer before 50 is young). If you see lots of cancers and those showing up at young ages, talk with your family doctor about Lynch syndrome. If he or she is not knowledgable about it, look for a genetic centre with a counsellor you can speak to.
The Treatment for Lynch Syndrome
Lynch syndrome cannot be cured. It often manifests itself as cancer, which can be treated and often cured. However, the underlying genetics cannot be repaired, at least not yet. While there have been some early successes with aspirin therapy to reduce the incidence of colon cancers in people with Lynch, the closest thing to an actual cure for the genetic syndrome is the same as it is with BRCA—to remove the organs in which cancers are most likely to occur(16). Whenever colon cancer occurs in a known case of Lynch syndrome, a subtotal colectomy is generally recommended for both males and females. This entails an almost complete removal of the large intestine, with the small intestine then being connected to a small portion of the rectum to ensure continued bowel control. For women known to have Lynch, a removal of some or all of the reproductive organs—at minimum the uterus, and often the ovaries and fallopian tubes as well—is recommended as soon as their biological families have been completed.
While surgery is one method used to limit the effects of Lynch syndrome, the measure most commonly used is regular surveillance. It is for this reason that identifying people who carry Lynch mutations is so important. Colonoscopies are carried out every one to two years in carriers(17). Not only can any tumours then be detected early, but even better, the polyps which become cancerous over time can be found and snared (removed) even before they turn malignant. When warranted by family or personal history, this surveillance by way of colonoscopy is supplemented by gastroscopy, ultrasound, and MRI procedures to watch for the development of cancer in organs that are the most susceptible. These rigorous surveillance measures can be justified only in people who are suspected or confirmed to have Lynch syndrome.
More People Need to Know More about Lynch Syndrome
More people need to know more about Lynch syndrome: doctors, patients, and the average person. If statistical estimates are correct, about 1.1 million people in North America alone (some estimates are as high as 1.5 million) have Lynch(18). Yet as few as 55,000 of these cases are confirmed. That means there are more than one million people who have Lynch but are not getting regular surveillance for a condition which gives them a 60-80% chance of getting colon cancer. That also means there are 500,000 women with a dramatically elevated risk of uterine cancer who are not being advised of surgical options to reduce their risk. And that is a lot of people.
For more information about Lynch syndrome, check out Lynch Syndrome International at http://lynchcancers.com. To read the journey of one Lynch syndrome carrier, including his two occurrences of colorectal cancer, check out the links to my book at the bottom of this blog— links where you can also read an excerpt from the narrative.
(1) The likelihood is actually about 60% for carriers: http://www.cancer.gov/cancertopics/pdq/genetics/breast-and-ovarian/HealthProfessional/page2
(2) A rare disease is defined as one that occurs in about 1 in 1500 people: http://www.rarediseases.org/rare-disease-information
(3) This according to Kory Jasperson, Vice-Chair of the Hereditary Colon Cancer Foundation: http://youtu.be/cmuEckDiEEQ. Variations of this number exist and some say it is as low as 5%. However, because we are talking about people who are believed to have Lynch (based on extrapolation from existing data)) but who have not actually been tested, there is no way to be sure.
(4) This according to Kory Jasperson, Vice-Chair of the Hereditary Colon Cancer Foundation: http://youtu.be/YPfie1bElno.
(8) This according to Kory Jasperson, Vice-Chair of the Hereditary Colon Cancer Foundation: http://youtu.be/YPfie1bElno
(16) There is a great deal of talk and debate around prophylactic (preventative) surgeries for people with hereditary cancer syndromes like Lynch. Some surgeons recommend removal of most of the large intestine; however, it has not been shown that this is a more effective measure than regular surveillance for people who have not yet had an incidence of colon cancer. For women, it is recommended that both the uterus and ovaries be removed once they have completed their families as cancers in both of these organs are difficult to screen for. Of course, the removal of any organ has its own risks and associated side effects. http://www.mayoclinic.org/diseases-conditions/lynch-syndrome/basics/treatment/con-20025651
(17) In the average population, colon cancers are slow to appear and are usually slow-growing. This is why recommendations are for people to get a colonoscopy at 50 years of age and then 5-10 years after that. However, in people with Lynch, colon cancers appear quickly and grow rapidly. As a result, colonoscopies need to be performed on a 1-2 year interval. http://www.cancer.net/cancer-types/lynch-syndrome
(18) This estimate is based on the number of people who have been diagnosed and the percentage of actual carriers that that number may represent (that is, 5%-10% of carriers).
His latest book, What I Learned from Cancer, is available in electronic form at his payhip.com site: http://bit.ly/wilfc-ebook. Physical copies of the book are available at the Prompters to Life web store, where shipping of the softcover edition is always free (except to the International Space Station). To order a paper copy of the book, visit: http://prompterstolife.com/shoppers