Once a cancer has been diagnosed, we must use our knowledge of biology, medicine, and clinical trials to plan treatment. Treatment can be curative or palliative (that is, with a goal of reducing symptoms or extending life, rather than effecting a cure).
Understanding cancer treatment requires a little bit of basic biology, and as with all of my more “science-y” posts, please forgive any oversimplification (but please also note that this complexity stands in stark contrast to the simplistic altmed cancer “cures”), or for overtopping the head of the hapless non-scientist.
As you recall from Cancer 101, cancer is a proliferation of abnormal cells. This fact alone, that the cells are actively dividing, gives us a target for therapy.
Cells go through particular phases in their lifetimes, but these phases aren’t as simple as “birth, growth, death”. The life of a cell is roughly divided into the cell cycle, during which the cell is preparing for and conducting cell division, and the G0 (G sub zero, or G-naught) phase, where the cell simply goes about all of it’s non-reproductive business, such as structural support and protein production. Normal tissue has a fairly balanced growth fraction, that is the number of cells dividing is roughly equal to the number of cells being lost (to normal programmed cell death and other normal attrition). Cancerous tumors have a higher growth fraction than normal tissue, that is the number of cells in cycle is higher than the number of cells being lost (to programmed cell death, etc.).
Continue reading “Cancer 201—treatment basics”
In Cancer 101, I gave some basics to understanding cancer. A commenter asked a good question, and our next lesson will attempt a simple answer.
The question regarded how a pathologist can tell if a cancer is “invasive” by looking at a specimen. Well, depending on the specimen, the answer changes, but let’s use the colon as an example. Most colon cancers start out as benign polyps. Eventually the cells in the polyp can become malignant, and after that, they can they can begin to grow through layers of normal cells.
Here is a diagram of a cancer of the colon at various stages. As you can see, at a certain point, the cancer begins to grow through each layer. The ability to grow through, or invade, other layers is one of the things that makes cancers behave in a nasty manner.
Here is a piece of colon cancer under the microscope. This could have been from a biopsy of a polyp, or from a tumor completely removed by a surgeon. The stripe of light purple cells labeled “normal muscle layer” should extend across uninterrupted. Instead, a glob of darker purple cells is growing through the muscle layer, destroying it. Once the cancer cells get to a blood vessel, they can go anywhere in the body (metastasize). That’s bad.
I hope that’s helpful.
Cancer is the second leading cause of death in the U.S., and at any moment directly affects almost 4% of the population, or about 10.8 million Americans. A diagnosis of cancer can be one of the most frightening moments in someone’s life, and yet most people understand little about the disease. I hear the same questions about cancer over and over again, so it’s well past time to give a bit of an explanation of this set of diseases.
Continue reading “Cancer 101”
OK, if you insist. This comes with the usual caveat directed at scientists that I know this is oversimplified, but I wish to reach the largest audience possible. Feel free to correct my mistakes, but please don’t bother me about oversimplification.
So here’s the deal. Several decades ago, it became scientifically fashionable to believe that most cancer had a viral cause. This belief coincided with the discovery that some viruses do cause cancer. And while it turns out that most cancers are not caused by viruses (probably), many of them are. Viruses can cause cancers in a number of ways, but since you said you were interested in HPV (human papilloma virus) we can use this as an example.
First, there is no scientific question about the causal relationship between HPV and cervical cancer (and certain oral cancers, anal cancers, and penile cancers, but we’ll use cervical cancer as shorthand for all of them). There is excellent epidemiologic evidence to support this, and virologic evidence that proves it.
Now that we’ve got that out of the way, how does this cancer virus thing work?
Continue reading “DrPal, tell us more about HPV and cancer”