Dr. Maryam Mirzakhani, courtesy Stanford News Service
At 2:20 am, I gave up my quest to try to sleep and decided to work on my post. When I opened my laptop, a picture of sweet Y, a really supportive former labmate and truly kind friend, was smiling at me. I had forgotten to close my Facebook page and a friend had shared Y’s smiling picture as an announcement of her passing away. Trembling in total shock and disbelief, I frantically contacted a few of my other labmates and anxiously waited to hear what had happened. Y had passed away due to an invasive ovarian cancer.
Over the past few months, my life has been filled with stories of loss – all due to cancer.
My summer began with the devastating news of the passing of one of my role models from my childhood. Dr. Maryam Mirzakhani, the first woman to ever receive the Fields Medal, the equivalent of a Nobel prize in mathematics, passed away due to breast cancer. (If you are interested to know more about her achievements, read this.)
When I was just beginning high school, Dr. Mirzakhani made the news by winning the gold medal in the International Mathematical Olympiad two years in a row. Many Iranian girls looked up to her and were fascinated by her achievements and hard work through the years. Her death came as a shock and was a true loss to the math world and to women in the STEM community. Two losses from cancer, coming so close together, is what inspired me to write this post.
Cancer is the disease of the century: one in every two Canadians is expected to develop cancer in their lifetime. There are many different mechanisms at play when a normal cell becomes cancerous, which is still under investigation. The common belief is that a group of cells just won’t stop growing and never dies, and overpopulates a specific region in the body. This causes problems for the function and viability of the other cells. As Dr. Sidartha Mukherjee, author of the best selling “The Emperor of All Maladies: A Biography of Cancer” puts it: “there is deep commonality between all different types of cancer but it gets a different face in each one of them.”
Can we screen for cancer?
There are common and well-known risk factors for certain cancers, such as smoking and lung cancer. There are also cases where a perfectly healthy person with a healthy lifestyle and diet gets cancer. The main culprit in such cases seems to be genetic mutations. One of the most notorious is a mutation in the BRCA genes. Which, incidentally, has a strong causal relationship to cancer in breast and ovarian tissue.
During DNA replication inside cells, there are certain checkpoints where defects in the DNA are detected and repaired. When BRCA1 and BRCA2 genes are mutated, the lack of these proteins at the checkpoints will result in an overlooked, damaged DNA strand, which in turn can result in a cancerous cell. It is estimated that someone who inherited BRCA mutations will have a 40-85% chance of developing breast cancer at some point.
Fortunately, screening for genetic mutations such as BRCA is available these days. A team of researchers at University of Toronto has started a cost-effective program called the screen project. Through this program, individuals who might have a genetic predisposition to cancer, due to a family member with cancer, can get an affordable screen. I contacted Dr. Mohammad Reza Akbari, one of the principal investigators of the screen project, to get some information for Signals’ readers about this project and how it pertains to breast cancer.
Q: How can an early screen be helpful in the diagnosis and treatment of breast cancer? Can it replace imaging tests such as mammography, or is it a complementary test?
A: Genetic screening is not a replacement for imaging screening. The main purpose of imaging screenings is to detect cancer after it happens in early stages, but the main goal of genetic screening is to identify the people at very high risk for breast cancer and prevent it from happening. Then, we can offer more intensive imaging screening to those at high risk to be able to detect cancer at an earlier stage. Also, we can offer them more targeted treatments after diagnosis, if we know they are carriers of the mutation.
Q: What would a positive result mean? And what are the next steps to take for a patient with positive results?
A: A positive result means that the tested individual carries a pathogenic mutation in one of the BRCA1 and/or BRCA2 genes. This mutation increases the risk of breast cancer up to 80%. The next step will be to offer full genetic counseling to carriers to understand the options they have for preventing or reducing their cancer risk and also the things they can do to detect cancer at early stages.
Q: How accurate would a DNA screen be, and are there any chances of false negatives? Or if someone receives a negative result, does that mean they are safe?
A: The DNA test is much more accurate than all other types of cancer test we currently use. For example, the false positive rate for this test is zero while false positive rates for some tests – like PSA – is up to 75%. The false negative rate for this test is not zero, but it is very close to it. A negative result does not mean that people are safe, it just means that they are not at higher risk due to carrying a mutation in these genes.
Q: When looking for statistics regarding BRCA mutations and a likelihood of breast cancer, I came across a range of 40-85% of increased probability of breast cancer with a BRCA mutation. Why is there such a big range in the statistics?
A: The risk is different based on the type of the mutation and the gene mutated, and also the population that has been studied.
Q: What are the differences between this screen and other DNA screens such as the one 23andme provides to people?
A: Tests like 23andme test for a couple of known mutations, such as Jewish specific mutations in BRCA genes, while our test screens the entire coding regions of the genes in search for any mutation. Additionally, we provide a guided direct-to-customer service. Meaning that a genetic counselor will contact the person with positive results and ensure they receive adequate information to make the best decision for their health.
Immunotherapy: the new development in cancer treatment
A novel approach to treating cancer is immunotherapy. The main idea is to use the body’s own immune system to attack cancerous cells. Normally, our immune system is able to get rid of foreign cells and invaders. However, cancerous cells typically do not have a “foreign” cell flag or antigen that is detected by the immune cells. Even in cases where they do, the immune system might not be able to defend and get rid of them.
Immunotherapy approaches either help the immune system by flagging cancerous cells that need to be destroyed or provide it with man-made immune system components and proteins to boost the patient’s immune system. Such strategies have been shown to be effective in slowing or stopping cancer growth and spread.
When a foreign body attacks or is multiplying in our body, the first line of defense are T cells. Many immunotherapy techniques focus on ways to “train” the body’s T cells into recognizing and attacking the cancerous cells. Recently, the U.S. Food and Drug Administration (FDA) approved a new immunotherapeutic drug called Tisagenlecleucel, or Kymriah,
by Novartis for the treatment of acute lymphoblastic leukemia (ALL) in children and young adults. Kymriah is called a CAR-T gene therapy. You can learn more about CAR-Ts and other recent FDA approvals here, and the Canadian Cancer Society explains different immunotherapy techniques and advances here.
Even though it’s really promising, there are reports of serious side effects to the use of immunotherapy strategies. And, although immunotherapy for a certain type of breast cancer has shown promise, this approach has yet to be proven effective in treating solid tumours. One reason is the complexity of a tumour’s structure and a variance in the type of cellular markers found in different layers of cells within it. Also, different types of cancerous cells and antigens might be active within a tumour structure and one of the main challenges for treatment is developing the appropriate combination of drugs to use against a specific tumor. More research is needed to make use of the knowledge in this field and develop clinically relevant therapeutics.
Reading about cancer and how complex it is has been eye opening for me. The light at the end of the tunnel is that there are amazing researchers, oncologists, physicians, surgeons, social workers and caretakers who are working on finding a cure and ways to make a cancer patient’s life easier. While a definite cure is not in sight at the moment, as Dr. Mukherjee eloquently reminds us at the end of his book: “… to keep pace with this malady, you need [ed] to keep inventing and reinventing, learning and unlearning strategies. “ Hopefully there will be a day when an effective strategy against cancer is at hand.
(To find a Canadian cancer trial, click here.)
