I always think that the best way to understand cancer (especially quickly!) is by understanding the life cycle of the cell. Cancer is caused by problems in the DNA, so you need to understand a little bit about how DNA can get damaged in order to more easily understand cancer.
Remember the process of Mitosis? Well, you need to review it if you don’t. 🙂 During mitosis, mistakes can sometimes be made when copying the DNA. If one (or more) of those mistakes happens to be in an unfortunate place, it can give the cell instructions to do something that it is not supposed to do. These wrong instructions often tell the cell to replicate itself a lot faster than it should, which is why a tumor grows faster than the normal cells around it.
Another way that DNA can get mistakes is if a mature cell is exposed to some kind of damaging force…like certain medications, x-rays, UV from the sun, smoking, or radiation. If a cell’s DNA is damaged by any of those things, it first tries to repair the damage. But if the cell undergoes Mitosis before the DNA can be repaired, or if the damage cant be repaired at all, then the new DNA mistakes will be inherited by the 2 daughter cells when it divides. And if those DNA mistakes happen to be in an unfortunate place, then you have the same problem that I explained above…a cell that misbehaves and replicates a lot faster than the normal cells around it.
Understanding how cancer is ’caused’ will help you remember a lot of details about it. For example, the older you get, the more our bodies are exposed to things that could potentially damage our DNA. In addition, our cells have also gone through more and more cycles of Mitosis, which increases the chances that an occasional DNA mistake will be made. As the mistakes in our DNA accumulate over time, the chance that one of those mistakes will be in an unfortunate location that causes cancer also increases. That’s why cancer is so much more common in the elderly, who have had a lifetime of DNA mistakes slowly building up in their cells. In kids, on the other hand, cancer is still relatively rare.
Another detail that becomes more obvious from this explanation is that the cells that are most likely to become cancerous are the same cells that experience the most mitosis. For example, skin cells and GI cells divide and replace themselves relatively rapidly, and both cell types are very common locations for cancer. Brain cancer, on the other hand is much more rare because brain cells don’t go through Mitosis very often, so there’s fewer chances that those cells with get DNA mistakes.
Pay attention, because now I’m REALLY going to blow your mind…
Not only are the skin and GI two of the most common systems to get cancer, but they are also the two systems that experience the most common side effects from chemo and radiation therapy. And that’s because chemo and radiation therapies actually work by causing damage to both cancerous AND healthy cells.
Wait a second…WHAT?!?! How’s that work?
I’m glad you asked. Remember how I said that cancer cells go through mitosis more often than healthy cells? Well, if a cell has some serious DNA damage when mitosis occurs, than there’s a high likelihood that cell is not going to survive the process. AKA: Cell Death. So the reason that chemo and radiation can sometimes get rid of cancer is because the cancerous cells get damaged DNA, start mitosis shortly after, and die. They just don’t have the time needed to repair the damage before mitosis happens.
The healthy, non-cancerous cells, however, start mitosis less frequently than the cancerous cells, which increases the chance that any chemo and radiation-caused DNA damage can be repaired. Even so, some healthy cells are going to start Mitosis before the DNA damage can be fixed, and those healthy cells will end up dying, too.
The healthy cells at the highest risk of dying from chemo/radiation-caused DNA damage are…
(wait for it…)
…the same cells that tend to go through mitosis most frequently! Like skin and GI cells! Are you seeing a pattern here yet? This explains the most common symptoms we see for chemo and radiation: skin breakdown, GI lesions, and hair loss (another quickly replicating cell in the body). But we don’t see as much nervous system or cardiac damage because those cells do not replicate nearly as often.
One More Observation
Let’s use mitosis, DNA damage, and the cell cycle to draw one final conclusion about cancer. Patient’s who survive and become cancer free can sometimes discover that one of the more unfortunate long-term side effects of chemo and radiation is…the development of another type of cancer!!
It seems crazy that the treatment could also cause the disease down the road. But when you think about the cell damage that is done to healthy cells during chemo treatment, it makes sense. They have been exposed to DNA damage that can eventually turn into enough DNA mistakes to turn the once-healthy cells cancerous. This will not always be the same cancer that a person originally had, it could be a completely new cancer in a new system (is anybody thinking about the skin or GI system, maybe?).
When studying cancer, it is best to focus on having a general understanding of how cancer develops and progresses, what are some signs of cancer (hint: it will usually be related to the system the cancer is in!), what are the treatments (memorize some of the classifications of chemo drugs, and be able to recognize 1-2 of the common drug names in each classification). And of course, nursing and safety considerations for the treatments. This will usually include comfort measures related to nausea, skin breakdown, hair loss, and also teaching related to chemo/radiation, safety issues when administering radiation or chemo, and teaching related to treatments.