Over the last 20 years, deaths from chronic non-communicable diseases have surpassed deaths from acute infectious diseases in all regions of the world, except Africa.
Today, 60% of all deaths worldwide are from chronic non-communicable causes, led by cardiovascular disease, cancer, chronic respiratory disease, and diabetes. In the developed world, non-communicable diseases account for 86% of all deaths; in the developing world, they account for just under 50%.
Cancer accounts for a significant portion of this growing burden. In 2006, the disease will claim approximately seven million lives worldwide, and another 11 million new cases will be diagnosed. Cancer accounts for one in eight deaths – more than AIDS, tuberculosis and malaria combined.
Throughout the world, some 25 million people are living with the disease. A substantial number of them experience a significant reduction in their quality of life due to physical pain, mental anguish and economic hardship.
The rapid growth in the global cancer burden comes at a time when overall age-adjusted cancer incidence and mortality rates are actually falling in most parts of the developed world. In the USA, for example, the overall cancer incidence rate fell 7.6% between 1992 and 2002, and the overall cancer mortality rate fell 10% between 1991 and 2002.
Unfortunately, these declines have been offset by increases in cancer incidence and mortality in low- and middle-income countries. Worldwide, the number of new cancer cases per year is expected to top 15 million, and the number of deaths could grow to as many as 12 million by 2020.
At least 70% of these deaths will be in economically developing countries, where survival rates (20–30%) are often less than half those in the USA and other developed nations (more than 60%). In fact, some 80–90% of cancer patients in developing countries present with late-stage, terminal cancer.
THE TOBACCO FACTOR
Several factors account for the increase in cancer cases and deaths: growing and ageing populations, tobacco use, infectious agents, and poor diet and exercise habits. Limited access to information about cancer and healthy lifestyle behaviours, and early detection and treatment programmes also have an effect.
Tobacco use is the single greatest preventable cause of cancer. Today, nearly a billion men and more than 250 million women are regular smokers – about 20% of the world's population. If current trends continue, tobacco use will kill about 650 million people living today, including as many as 325 million of the world's current children and teenagers. Lung cancer and heart disease will account for the majority of these deaths.
Ironically, as developed nations have succeeded in reducing tobacco use through regulation and intervention, tobacco use in developing nations has grown as the industry has shifted its efforts to less-protected markets.
By 2025, tobacco will account for nearly seven million deaths annually in low- and middle-income nations. China alone predicts two million tobacco-related deaths annually by 2025.
Half of the victims of tobacco-related disease will die in middle age (35–65), just when they are needed most to manage and support their personal households and local economies.
Options to reduce tobacco-related disease and death are currently limited. Well-designed cessation counselling programmes are proven to increase smoking cessation rates and are even more effective when used in conjunction with drug therapy, such as nicotine replacement and bupropion, as well as the newer agents rimonabant and varenicline.
Unfortunately, these therapies are expensive, which limits their availability, and few have been widely tested with smokeless or chewing tobacco use, which is a serious issue in a number of developing regions, including India.
One important advance in tobacco control is the passing of the world's first public health treaty: the Framework Convention on Tobacco Control (The FCTC). The FCTC came into force on 27 February 2005.
The treaty is designed to reduce the devastating health and economic impacts of tobacco through provisions that encourage countries to enact comprehensive bans on tobacco advertising, to place health warnings on tobacco packaging, to ban the use of misleading terms such as 'light' and 'mild', to protect citizens from exposure to tobacco smoke in public places, to combat smuggling and to increase tobacco taxes.
As of 1 January 2006, 168 countries had signed the FCTC, and 116 had become party to it.
THE ROLE OF INFECTION
Infectious agents currently account for about a quarter of all cancers in low and middle-income countries and 17% of all cancers worldwide.
Infectious agents associated with cancer include human papillomavirus or HPV (cervical cancer), hepatitis B and C (liver cancer), and Helicobacter pylori (stomach cancer), among others. In some cases, vaccination and early detection can significantly reduce the number of new cancer cases and deaths.
Unfortunately, technologies commonly used in high-income countries, such as the Pap test, are often prohibitively costly in other parts of the world. Low-cost interventions, such as visual inspection for cervical cancer using acetic acid or Lugol's iodine, may offer effective alternatives for some countries.
Combining these low-tech interventions with newer high-tech interventions, such as HPV testing, is under investigation and may offer further options for early detection.
Cryosurgery as an alternative to colposocopy may be warranted in regions where access to quality treatment centres is limited. Two new vaccines for HPV will be available soon and could further reduce cervical cancer incidence and mortality rates if they can be employed on a widespread basis.
Poor diet and lack of exercise may account for up to a third of all cancer deaths in the developed world. Although the number of overweight and obese adults is higher in the developed world, the developing world is quickly catching up. Today, over a billion adults worldwide are overweight. Of these, nearly a third (300 million) are clinically obese.
The prevalence of obesity ranges from below 5% in China, Japan and most African nations to more than 75% in urban Samoa. However, even in countries such as China, where prevalence is low, obesity rates in some cities are almost 20%.
Perhaps even more troubling is the increasing number of overweight and obese children. Worldwide, 22 million children under age five are estimated to be overweight.
Increases in overweight and obesity reflect societal changes. With the global spread of consumer cultures originating in economically developed nations, people in low- and middle-income countries are increasingly adopting Western lifestyles and behaviours, including changes in diet and physical activity. Shifts towards less physically demanding work have been accompanied by the globalisation of food markets and the spread of the fast-food industry.
Being overweight or obese increases the risks of breast cancer (among postmenopausal women) as well as cancers of the colon, prostate, endometrium, kidney, gallbladder and others. Many risk factors for these cancers are also associated with the development of other chronic diseases, including type 2 diabetes, cardiovascular disease, hypertension and stroke.
Reducing the risk of cancer through better diets, more physically active lifestyles and healthy weight maintenance will also reduce the risk of these diseases. Moreover, there is increasing evidence that the same lifestyle changes that reduce the risk of cancer also affect the quality of life, and potentially the long-term survival rates, of cancer survivors. Among necessary steps to reduce the growth in overweight and obesity worldwide are changes in public policy, health education and urban design.
THE TASK AHEAD
In many ways, the cancer situation in low- and middle-income countries is the same as it was in the USA 25, 50 or even 75 years ago. These regions are often characterised by accelerating cancer incidence and mortality rates, the absence of robust prevention and detection efforts, a scarcity of high-quality cancer information, limited access to quality cancer care, and a host of infrastructure issues.
Huge disparities in the capacity of healthcare systems, governmental programmes and non-governmental organisations also contribute substantially to the unequal burden of cancer in these countries.
Many emerging nations have few, if any, early cancer detection and prevention efforts, and provide only limited treatment options. Since far more cancers are detected at later stages in these countries, the success rates are lower, even when effective treatment options are available.
Currently, more than three-quarters of all healthcare expenditure is directed to patients in the developed world. To make matters worse, public debate around the growing burden of cancer and other chronic, noncommunicable diseases is limited. As a result, few policymakers, public health officials or healthcare practitioners are taking adequate steps to prepare for these significant disease trends. The very first step in preparing for the future is education and debate.
The decline in cancer incidence and mortality rates in developed nations is evidence that cancer can be controlled. However, without aggressive intervention, there is little likelihood that similar results will be realised in developing nations in the near future.