SARS or Severe Acute Respiratory Syndrome, an unusual form of pneumonia, has grabbed news headlines recently, with more than 3500 reported cases worldwide and 5% mortality rate. The hardest hit area is China (Guang Dong & Hongkong) accounting for more than 80% of the cases. The outbreak reached its peak around the last week of March and reported new cases are now on the decline. Unprecedented international cooperation by some of the most advanced medical centers help to identify its cause and hasten development of drugs/vaccines to stop the spread of this viral disease.
Now comes another disturbing report from the World Health Organization of the looming threat of increasing cancer rates. Here is an excerpt from the press release.
Global cancer rates could increase by 50% to 15 million by 2020
3 April 2003 | GENEVA -- Cancer rates could further increase by 50% to 15 million new cases in the year 2020, according to the World Cancer Report, the most comprehensive global examination of the disease to date. However, the report also provides clear evidence that healthy lifestyles and public health action by governments and health practitioners could stem this trend, and prevent as many as one third of cancers worldwide.
The predicted sharp increase in new cases - from 10 million new cases globally in 2000, to 15 million in 2020 - will be mainly due to steadily ageing populations in both developed and developing countries and also to current trends in smoking prevalence and the growing adoption of unhealthy lifestyles.
In the year 2000, malignant tumours were responsible for 12 per cent of the nearly 56 million deaths worldwide from all causes. In many countries, more than a quarter of deaths are attributable to cancer. In 2000, 5.3 million men and 4.7 million women developed a malignant tumour and altogether 6.2 million died from the disease. The report also reveals that cancer has emerged as a major public health problem in developing countries, matching its effect in industrialized nations.
Cancer by the Numbers
Lung cancer is the most common cancer worldwide, accounting for 1.2 million new cases annually; followed by cancer of the breast, just over 1 million cases; colorectal, 940,000; stomach, 870,000; liver, 560,000; cervical, 470,000; esophageal, 410,000; head and neck, 390,000; bladder, 330,000; malignant non-Hodgkin lymphomas, 290,000; leukemia, 250,000; prostate and testicular, 250,000; pancreatic, 216,000; ovarian, 190,000; kidney, 190,000; endometrial, 188,000; nervous system, 175,000; melanoma, 133,000; thyroid, 123,000; pharynx, 65,000; and Hodgkin disease, 62,000 cases.
The three leading cancer killers are other than the three most common forms, with lung cancer responsible for 17.8 per cent of all cancer deaths, stomach, 10.4 per cent and liver, 8.8 per cent.
Industrial nations with the highest overall cancer rates include: U.S.A, Italy, Australia, Germany, The Netherlands, Canada and France. Developing countries with the lowest cancer were in Northern Africa Southern and Eastern Asia. (A complete list of cancer rates by countries can be found at http://www-dep.iarc.fr/).
Lung cancer in women
Lung cancer strikes 900,000 men and 330,000 women yearly. Among men, smoking causes more than 80 per cent of lung cancer cases. In women, smoking is the cause of 45 per cent of all lung cancer worldwide, but more than 70 per cent in North America and Northern Europe. In both men and women, the incidence of lung cancer is low before age 40, and increases up to age 70 or 75.
The rise in female smoking prevalence is a major public health concern. In the US, more women die from smoking-induced lung cancer than from breast cancer and in some Nordic countries, including Iceland and Denmark, female lung cancer deaths have begun to outnumber male victims. Considering that in several European countries up to 50 per cent of young women are now regular smokers, this will cause a disease burden that significantly reduces women's health in decades to come.
Colon cancer
Cancers of the colon and rectum are rare in developing countries, but are the second most frequent malignancy in affluent societies. More than 940,000 cases occur annually worldwide, and nearly 500,000 die from it each year.
A major cause is a diet rich in fat, refined carbohydrates and animal protein, combined with low physical activity. Genetic susceptibility appears to be involved in less than five per cent of cases. Epidemiological studies suggest that risk can be reduced by decreasing meat consumption (particularly processed meat) and increasing the intake of vegetables and fruit. Migrant populations rapidly reach the higher level of risk of the adopted country, another sign that environmental factors play a major role.
"The World Cancer Report tells us that cancer rates are set to increase at an alarming rate globally. We can make a difference by taking action today. We have the opportunity to stem this increase. This report calls on Governments, health practitioners and the general public to take urgent action. Action now can prevent one third of cancers, cure another third, and provide good, palliative care to the remaining third who need it, " said Dr. Paul Kleihues, Director of the International Agency for Research on Cancer (IARC) and co-editor of the World Cancer Report.
Examples of areas where action can make a difference to stemming the increase of cancer rates and preventing a third of cases are:
The World Cancer Report - The major findings
Tobacco, the case for primary prevention
Tobacco consumption remains the most important avoidable cancer risk. In the 20th century, approximately 100 million people died world-wide from tobacco-associated diseases (cancer, chronic lung disease, cardiovascular disease and stroke). Half of regular smokers are killed by the habit. One quarter of smokers will die prematurely during middle age (35 to 69 years).
The lung cancer risk for regular smokers as compared to non-smokers (relative risk, RR) is between 20 and 30 fold. In countries with a high smoking prevalence and where many women have smoked cigarettes throughout adult life, roughly 90 per cent of lung cancers in both men and women are attributable to cigarette smoking. For bladder and renal pelvis, the RR is five-six but this means that more than 50 per cent of cases are caused by smoking.
The RR for cancers of the oral cavity, oral cavity, pharynx, larynx and squamous cell carcinoma of the oesophagus is greater than six, and three-four for carcinomas of the pancreas. These risk estimates are higher than previously estimated and unfortunately, additional cancer sites with a RR of two-three have been identified as being associated with tobacco smoking, including cancers of the stomach, liver, uterine cervix, kidney (renal cell carcinoma) nasal cavities and sinuses, esophagus (adenocarcinoma) and myeloid leukaemia.
Involuntary (passive) tobacco smoke is carcinogenic and may increase the lung cancer risk by 20 per cent. There is currently no evidence that smoking causes breast, prostate or endometrial cancer of the uterus.
Infection and cancer: intervention is key
In developing countries, up to 23 per cent of malignancies are caused by infectious agents, including hepatitis B and C virus (liver cancer), human papillomaviruses (cervical and ano-genital cancers), and Helicobacter pylori (stomach cancer). In developed countries, cancers caused by chronic infections only amount to approximately 8 per cent of all malignancies. This discrepancy is particularly evident for cervical cancer. In developed countries with an excellent public health infrastructure and a high compliance of women, early cytological detection of cervical cancer (PAP smear) has led to an impressive reduction of mortality while in other world regions, including Central America, South East Africa and India, incidence and mortality rates are still very high. Today, more than 80 per cent of all cervical cancer deaths occur in developing countries.
Vaccinations could be key to preventing these cancers. HBV vaccination has already been shown to prevent liver cancer in high-incidence countries and it is likely that human papillomavirus (HPV) vaccination will become a reality in 3 to 5 years.
In the gastro-intestinal tract (GIT), any chronic tissue damage with necrosis and regeneration carries an in creased cancer risk, e.g. consumption of very hot beverages (squamous cell carcinoma of the esophagus), gastro-oesophageal reflux (adenocarcinoma of the esophagus), chronic gastritis induced by H. pylori infection (stomach cancer), Crohn's disease (cancer of the small intestines) and ulcerative colitis (colon cancer).
The Western lifestyle and its health risks
The Western lifestyle is characterized by a highly caloric diet, rich in fat, refined carbohydrates and animal protein, combined with low physical activity, resulting in an overall energy imbalance. It is associated with a multitude of disease conditions, including obesity, diabetes, cardiovascular disease, arterial hypertension and cancer.
Malignancies typical for affluent societies are cancers of the breast, colon/rectum, uterus (endometrial carcinoma), gallbladder, kidney and adenocarcinoma of the oesophagus. Prostate cancer is also strongly related to the Western lifestyle, but there is an additional ethnic component; black people appear to be at a greater risk than whites and the latter at higher risk than Asian populations. Similar lifestyles are associated with a similar tumour burden. Since they have a common cause, these neoplasms typically go together. There is no region in the world that has a high incidence of breast cancer without a concurrent colon cancer burden.
Obesity is spreading epidemically throughout the world. It visualizes a chronic energy imbalance and is an independent predictor of an increased cancer risk, particularly for carcinomas of the uterine endometrium, kidney and gall bladder.
Nutrition and cancer - the good news
Stomach cancer is among the most common malignancies worldwide, with some 870,000 cases every year, and 650,000 deaths. About 60 per cent of cases occur in developing countries, with the highest incidence rates coming in Eastern Asia, the Andean regions of South America and Eastern Europe. The good news is that stomach cancer is declining world-wide, in some regions almost dramatically. In Switzerland and neighbouring European countries, the mortality fell by 60 per cent within one generation. If this trend continues, stomach cancer may in some world regions become a rare disease during the next 30 years. The main reason for this welcome development is the invention of the refrigerator, allowing fish and meat preservation without salting. The drop in incidence and mortality rates is therefore particularly impressive in Nordic countries in which fish consumption is traditionally high, e.g. Iceland. In populations that still prefer salty food, e.g. Portugal and Brazil (salted cod, bacalao), Japan and Korea (salted pickles and salad), stomach cancer rates are still high but have also started to decline significantly. An additional factor contributing to this trend is the availability in many countries of fresh fruit and vegetables throughout the year.
Cancer prevention: a healthy diet can help!
Epidemiological studies indicate that the frequent consumption of fruit and vegetables may reduce the risk of developing cancers of epithelial origin, including carcinomas of the pharynx, larynx, lung, oesophagus, stomach, colon and cervix. Recent data from the European Prospective Investigation into Cancer and Nutrition (EPIC), suggests that a daily consumption of 500 grams (1.1 lbs.) of fruits and vegetables can decrease incidence of cancers of the digestive tract by up to 25 per cent.
The report also says that given the multi-faceted impact of diet on cancer, many countries should encourage consumption of locally produced vegetables, fruit and agricultural products, and avoid the adoption of Western style dietary habits. IARC says that such actions would have health benefits beyond cancer, since other common non-communicable diseases, notably cardiovascular disease and diabetes, share the same lifestyle-related risk factors.
Early detection - the best strategy second to primary prevention
The best possible prevention against cancer remains the avoidance of exposure to cancer-causing agents (eg tobacco, industrial carcinogens, etc): this is called primary prevention.
There is sound evidence that the recent decline in cancer mortality observed in several countries is to a significant extent due to early detection. Responsible for this success are not only improvements in imaging (mammography, magnetic resonance (MR) and computed tomography (CT) imaging), but also a higher degree of disease awareness and educational programmes on typical early symptoms. Most successful so far has been the early detection of cervical cancer by cytology and of breast cancer by mammography. A recent analysis by an IARC Working Group concluded that under trial conditions, mammography screening may reduce breast cancer mortality by 25-30 per cent and that in nation-wide screening programmes a reduction by 20 per cent appears feasible. There is also emerging evidence that prostate cancer screening by assessment of serum PSA levels may result in lower mortality rates but management of early lesions is still very invasive. For colon cancer, colonoscopy is considered the gold standard although its application in population-based screening programmes would require considerable medical resources.
Cancer control strategies
The aim of cancer control is a reduction in both the incidence of the disease and the associated morbidity and mortality, as well as improved life for cancer patients and their families. In addition to substantial opportunities for primary prevention, the World Cancer Report also emphasizes the potential of early detection, treatment and palliative care. It urges all countries to establish comprehensive national cancer control programmes, aimed at reducing the incidence of the disease and improving the quality of life for cancer patients and their families. In developing countries in particular, where a large proportion of cancers are detected late in the course of the disease, efforts to achieve earlier diagnosis and delivery of adequate palliative care and pain relief deserve urgent attention.
"By acting now, by the year 2020, countries can achieve significant reductions in cancer rates and in mortality from cancer. These opportunities exist, and the only question is whether we will take advantage of them for the benefit of all humankind." says Dr. Bernard Stewart, Director of Cancer Services, University of New South Wales and co-editor of the report.
--------------For further details, see the World Health Organization website.