Cancer cases increase, and greater impact is in countries with worse sociodemographic index

Cancer cases grew 26% from 2010 to 2019, when 23.6 million new diagnoses of the disease were recorded worldwide, compared to 18.7 million in 2010. In the same period, deaths caused by cancer increased by 20, 9%, from 8.29 million in 2010 to ten million in 2019.

In addition, more than 250 million years of life lost due to disability (DALYs) were recorded by the disease in the same year, an increase of 16% compared to the beginning of the decade. In 2010, that number was 216 million.

The results are from the analysis of the Global Weight of Cancer, published at the end of 2021, with data from 204 countries and territories, including Brazil. The report replaces the previous version, from 2017, which had pointed to a 33% growth in the number of new cases from 2007 to 2017.

The five main types of cancer reported, excluding non-melanoma skin cancers, were: lung, bronchus and trachea, corresponding to 18.3% of total cancer-related DALYs; colorectal (9.7%); stomach (8.9%); breast cancer (8.2%); and liver (5%).

According to experts, DALY is the indicator that best illustrates how a disease can affect population health. It calculates the years of life lost due to the disease (YLLs), referring to how many fewer years of life an individual had in relation to the population’s life expectancy, and the years living with the disease (YLDs), which may indicate loss of quality of life.

In addition to data on new cases and new deaths, the study evaluated the incidence and mortality in different regions according to the sociodemographic index (SDI), which gathers data on education, per capita income and number of children up to 25 years of age.

In the study, countries with high SDI registered for the first time cancer as the main cause of DALY in the last decade, compared to cardiovascular diseases, which still represent the main cause of mortality globally. Rich countries also recorded the highest number of cases globally and the highest incidence by age group.

In the countries with medium SDI, despite registering the highest absolute number of cancer-related DALYs and the highest number of deaths, the authors highlighted that these countries also concentrated the largest population range in the analysis.

Finally, the countries with the lowest SDI, despite having the lowest rates of cancer incidence and cases, had the greatest proportional increase in the last decade and the greatest weight of cancer in population mortality.

For the epidemiologist and professor at the USP School of Medicine, Paulo Lotufo, as well as other so-called non-communicable diseases (NCDs), the burden of cancer is directly associated with socioeconomic indices. “In São Paulo, there is a difference between middle and upper class women and those of lower classes in relation to the incidence of cervical cancer. The poorest women have a very high mortality from this type of cancer”, he says. .

In the last decade, there has also been a significant shift in the position of the main types of cancer, with colorectal cancer rising from the third to the second leading cause of years lost due to illness, and liver cancer from seventh to fifth position. Lung cancer remained, as in previous analyses, the most common type of cancer, except for non-melanoma skin cancer.

According to Maria Paula Curado, oncologist, head and neck surgeon and chief epidemiologist of the Department of Epidemiology and Statistics at Hospital AC Camargo, the fact that the number one cancer in cases and mortality is still lung cancer, which has a risk factor that can be prevented, worries. “Despite having several public policies to reduce smoking, it remains the most common cancer and the main cause of years lost due to disability”, she says.

Although the rates have improved compared to 2017, experts say that new cancer cases worldwide are expected to grow in the coming years due to the damming of new diagnoses caused by the Covid-19 pandemic.

According to the authors of the study, it is in the poorest regions that the greatest absolute growth in cancer-related cases and deaths was recorded between 2010 and 2019, and the upward trend may lead to the prediction that, by 2040, two thirds of global cases of cancer are reported in low SDI countries.

For Curado, cases in countries with a low sociodemographic index are probably held back, which explains this upward trend until 2040. “The so-called developing countries are now learning and adopting new diagnostic and treatment techniques, so there will be an increase in incidence in the next twenty years”, he says.

Regarding deaths, Lotufo says that there are two factors that explain this increase in mortality in low-SDI countries when compared to rich countries. “First, early diagnosis, which in developed countries is much more advanced. The other is life expectancy, which is also higher in these countries. The longer people live, the greater the chances of discovering some type of cancer, but will not necessarily be the cause of their death,” he explains.

The capacity of the health system is another limiting factor, according to Curado. “The cancer patient today in a public health system in low SDI countries suffers from the delay of exams, treatment, everything. The system is still unfair to these patients”, he says.