Dear students,
We have many times discussed about cancer during our lessons, especially when we study cell division.
In Malaysia, according to the data released by Ministry of Health some years ago, 1 out of 4 Malaysians is suffering from one type of cancer, that work out to be 25%. While in the UK, 1 in 3 people develop cancer during their lives; and about 1 out of 2 people in the US had cancer. That's scary!
There are about 200 different types of cancer, many are rare cancer while 20 cancer are common cancer types. In Malaysia, the most common cancer among women are breast cancer followed by cervical cancer; for men, it is prostate cancer followed by lungs cancer.
I find this article useful to deal with many questions most of us have on CANCER topic. You can either read the article below or you can get this article from www.newscientist.com or click here.
1. What exactly is cancer?
Cancer is the uncontrolled growth and spread of abnormal cells. These rogue cells invade and destroy healthy tissues around them. Without treatment, cancer is likely to kill.
2. What causes cancer?
For cells to turn cancerous, some of their genes must be damaged through mutation. People may inherit mutations that predispose them to cancer, but damage to genes happens during life too - when cells are exposed to carcinogens such as tobacco, for example. But cells do not easily turn cancerous: at least three "hits", or different types of damage or mutation, are usually needed.
Three main gene groups are involved in changes that lead to cancer.
Firstly, proto-oncogenes normally instruct cells to grow and divide. If these are mutated, they can turn into oncogenes that instruct cells to continue dividing when they should not - imagine a car with the accelerator jammed down.
Secondly, tumour-suppressor genes normally stop cells from multiplying. If they are damaged however, like a car brake failing, cell division goes unchecked.
The third gene group normally helps in the repair of damaged DNA, but if they fail in their task, cells will copy damaged DNA into their daughter cells as they divide.
3. How does cancer develop in the body?
Once a cell has transformed into a cancerous state, it begins to divide and multiply. In most cancers, these cells form a lump, or tumour, that can invade surrounding tissue. The tumour puts pressure on healthy cells around it, and may also secrete enzymes to break down that tissue.
By the time a tumour is detected, it will contain billions of cells. Cancerous cells produce growth factors that stimulate blood vessels to grow near them, enabling the tumour to build itself a nourishing blood supply. At later stages of the disease, cells break off the tumour and spread via blood or lymph vessels to seed secondary tumours in other parts of the body.
4. How common are different types of cancer?
After heart disease, cancer is the second most common cause of death in Western societies. In your lifetime, the risk of developing some kind of cancer is greater than one in three. There are perhaps 200 different types of cancer, but many are rare.
The most commonly diagnosed are non-melanoma skin cancers, many of which are easily treated. For men, the next most common three types of cancer are prostate, lung and bowel. For women, breast cancer is most prevalent, followed by lung and bowel. The number-one killer among all these is lung cancer, for both men and women. Outside of the West, liver cancer and cervical cancer are among the most common types.
photo above shows breast cancer
5. What factors may increase my risk of developing cancer?
Cancer is rarely triggered by a single factor. It usually results from an interplay between environmental factors - such as carcinogens or viruses - on one hand, and factors within the body - such as hormones and inherited genes - on the other. Among numerous carcinogens, tobacco towers over the rest as the biggest killer. In the US, for example, it is responsible for 30% of all cancer deaths and 87% of lung cancer deaths. Researchers estimate that a further one-third of cancer deaths can be blamed on other "lifestyle" factors, such as diet and obesity.
The incidence of lung cancer is highly correlated with smoking. Source:NIH.
Viruses can cause cancer by interfering with the genetic instructions in cells. The worst culprits for this are the hepatitis B virus, which can cause liver cancer, and the human papilloma virus, which can cause cervical cancer. The risk of developing cancer increases with age, simply because cancerous changes in cells usually take years to occur. Two of every three people diagnosed with cancer in the UK each year are over the age of 65.
6. What are some of the most promising new treatments for cancer?
Twentieth-century treatments for cancer - which relied mostly on poisoning tumours through chemotherapy or burning them away with radiation - remain the major weapons in our arsenal. But newer, more sophisticated treatments are starting, slowly, to make an impact.
7. Why does cancer appear so much more common today than in history?
More people are surviving into old age - not only in industrialised countries but worldwide - so there are more cases of cancer. As non-Western nations such as China and India smoke ever-more tobacco, worldwide prevalence could soar to a projected 16 million cases per year by 2020 - compared with 11 million cases today.
8. Do experts believe we could ever have a universal cure for cancer?
No. There are so many different types of cancer, and so many causes, that the idea of a universal cure is too simplistic. However, many experts are hopeful that a combination of better treatments and earlier detection, could whittle down death rates significantly. Some experts talk about "managing" cancer so that it becomes a chronic long-term condition, and not a direct threat to life.
To read more on cancer, click the links below.
1) National Cancer Institute - US
2) Get the facts about tobacco & cancer.
* secondhand smoke
4) Oprah - The Breast Cancer Monologue (+ real breast cancer stories)
