According to data from the World Health Organization (WHO), the most common are those of the lung, breast, colorectal, stomach and liver, which together account for almost half of the new cases of cancer that arise in the world each year. But what is this disease that scares so many people? Cancer can appear in virtually any part of the body when a cell mutates and divides uncontrollably. These diseased cells are able to induce the formation of new blood vessels to feed themselves and, when they reach the stage called metastasis, they use these open paths to spread throughout the rest of the body.
The lethality of cancer, that is, its ability to kill, depends on several factors. “First, the characteristics of the cancer itself, such as the speed with which it grows and invades tissues and organs”, says molecular biologist Roger Chammas, from the Faculty of Medicine of the University of São Paulo (USP). In addition, lethality depends on the ability of each organism to react and fight the disease. Finally, the existence of some type of effective treatment also weighs. “Testicular cancer, for example, which was once lethal, now has up to a 95% chance of being cured”, says Roger. Currently, experts have invested in two major areas in search of a definitive cure for the disease. One line of research focuses on trying to cut off the cancer’s blood supply, killing diseased cells for lack of food. Another works with the idea of stimulating the patient’s immune system, helping the body to recognize cancer cells in order to eliminate them.
LUNG – The most dangerous
With 1.2 million new cases each year, this is the most common type of cancer and also the one that kills the most in the world. It is dangerous because it is usually accompanied by other diseases associated with smoking, such as emphysema, which reduces lung capacity and can make surgery unfeasible, a treatment recommended in cases of non-advanced lung cancer. The main symptoms are cough, bloody sputum, chest pain, shortness of breath and inflammation in the bronchi. Ninety percent of cases are caused by smoking, an addiction that affects one third of the world’s adult population.
MAMA – National problem
It is the cancer that most kills women in Brazil. Around the world, there are about 1 million cases annually. The incidence increased tenfold in the 60’s and 70’s, but lethality was reduced thanks to prevention campaigns, which allowed earlier diagnosis of the disease. Self-examination, annual clinical examinations and frequent mammograms can reduce mortality in women prone to the problem, especially after 50 years of age. With the exception of the hereditary aspect, the risk factors for breast cancer are not well known, but it is possible that excessive consumption of alcoholic beverages is one of them.
COLO-RECTAL – Late symptoms
This cancer, which affects the region of the large intestine and rectum, is the third most common type in the world, with 940,000 new cases per year. In the United States, it is the second most deadly cancer, after the lung. The main symptoms are diarrhea, constipation, gas, pain in the abdomen, nausea, vomiting and weight loss. It is mainly caused by high-fat diets, meat consumption, obesity and physical inactivity. Symptoms usually only appear in more advanced stages, which makes this type of cancer quite lethal.
STOMACH – Risk diet
In terms of incidence, it is the fourth most common type in the world, with 870,000 cases per year. But it is the second that kills the most. This is because its symptoms are non-specific: weight loss, fatigue, lack of hunger, vomiting, nausea and abdominal discomfort. The result is that the disease often goes unnoticed until it reaches an advanced stage, when the cure is much more difficult. Diet is the biggest risk factor, especially the ingestion of foods preserved in salt or smoked, which makes stomach cancer more frequent in poor countries, where the use of this preservation method often replaces the refrigerator.
LIVER – Frightening evolution
Fifth in incidence (with 560 thousand new cases per year), it is the third that kills the most. It is usually associated with alcoholism and hepatitis B and C, but the disease can also be caused by the consumption of improperly stored grains, in which fungi grow that produce carcinogenic toxins. The main symptoms are pain and swelling in the abdomen, nausea, lack of appetite and yellowish skin. This type of cancer develops very quickly, and can double in size in just four months. The liver is also a common target for other cancers, which metastasize and spread throughout the body.
MELANOMA – Rare but feared
Melanoma is a rare cancer. There are about 130 thousand new cases per year, which corresponds to only 5% of all cases of skin cancer in the world. But, although rare, it is very lethal. As the disease appears as a mole on the skin, it is often ignored, being diagnosed too late. Other less frequent and dangerous cancers are that of the pancreas, which has no obvious symptoms, and the so-called “non-Hodgkin’s lymphoma”, which attacks cells in the ganglia and can spread quickly throughout the body.
100 thousand new cases per year in the world