Despite medical advances and efforts to prevent cancer, worldwide estimates show an increasing number of cases. There are various factors behind this increase, but above all they are due to population growth, greater life expectancy and lifestyle changes following social and economic development in the world’s poorest countries.
In Spain, figures predict 155,971 new cases of cancer in 2018 and 68,919 deaths. The most common type of cancer is prostate, followed by lung, colon, bladder, skin, rectal and kidney cancers. The highest percentage of deaths, 25.5%, occur in people with lung cancer, while skin cancer is the most benign type, causing just 0.6% of deaths.
One in five men have a greater risk of developing cancer, and in the case of women this figure is one in six. Asia is the region with the highest number of cancer deaths, 57.3% of all fatalities, as 60% of the world’s population is concentrated across this continent. In Europe, 20.3% of people who develop cancer subsequently die from the condition.
Incidence, prevalence and survival
The geographically defined incidence of cancer in a population can be calculated from databases created to identify and record all new cases of cancer diagnosed in that region. These records are also essential when it comes to determining patient survival rates at the population level and calculating the prevalence.
In 2012, WHO estimated there were 14.1 million new cases of cancer and 8.3 million cancer deaths worldwide (GLOBOCAN database).
Lung cancer is the main cause of cancer death among men, both in developed and developing countries, and has overtaken breast cancer as the primary cause of cancer-related death in women living in developed countries, although breast cancer remains the leading cause of death among women in underdeveloped countries.
In Spain, according to data published recently by REDECAN, there was a total of 247,771 new cases of cancer in 2015 (148,827 men and 98,944 women). The types diagnosed most frequently in 2015 were colorectal (41,441 cases), prostate (33,370 cases), lung (28,347 cases), breast (27,747 cases) and bladder cancers (21,093 cases).
In men, the five most commonly diagnosed tumours across Spain were prostate (33,370 cases), colorectal (24,764 cases), lung (22,430 cases), bladder (17,439 cases) and stomach cancers (5,150 cases). In women, the five most commonly diagnosed tumours in 2015 were breast (27,747), colorectal (16,677), cervical (6,160), lung (5,917) and bladder cancers (3,654 cases).
The prevalence is the number or proportion of the population with a certain disease over a given period or at a specific moment. The normal definition of prevalence is the number of patients diagnosed with a specific type of tumour who are still alive 1 year, 3 years or 5 years after the diagnosis.
Prevalence includes, therefore, both patients who received a recent diagnosis and those diagnosed in the past.
Prevalence is determined by survival, in other words, it is higher in tumours associated with a higher survival rate; for example, lung cancer is a very common tumour, yet the 5-year prevalence is relatively low because it has a high mortality rate. However, the prevalence of breast cancer and prostate cancer is very high because their incidence and survival are both high.
Patient survival is the main indicator of how effective a healthcare system is in terms of controlling the cancer. While it is usually quoted as the proportion, or percentage, of patients who are still alive 5 years after diagnosis, for many types of cancer it is also useful to know the 1- and 3-year survival rates, especially for the types associated with a high death rate.
This indicator is strongly influenced by the stage of the cancer at diagnosis and the effectiveness of the treatments. The survival rate depends on the type of cancer; with levels of 87% for prostate and breast cancer, 56% in the case of colorectal cancer and 11% of men and 19% of women for the case of lung cancer.
According to the Spanish National Institute of Epidemiology, over the period 2003–2012, the number of tumour-related deaths decreased by 1.32%/year, even though there was an overall increase in incidence.
These patterns reflect an improvement in cancer patient survival rates thanks to preventive efforts, early diagnosis campaigns and advances in treatments.