This week marks the 30th National Cancer Prevention and Awareness Week in China. A team led by Freddie Bray from the International Agency for Research on Cancer (IARC), an affiliate of the World Health Organization, recently published the latest cancer report in the Journal of Clinical Oncology, a journal with the highest impact factor in the medical field.
IARC's data indicates that in 2022, there were an estimated 19.974 million new cancer cases globally, with 9.744 million deaths.
Of these, lung cancer cases reached 2.481 million, accounting for 12.4% of all new cancer cases worldwide. This marks lung cancer's return to the top spot, surpassing breast cancer, which had overtaken it in 2020.
Lung cancer remains the leading cause of cancer death globally. In 2022, it resulted in 1.817 million deaths, accounting for 18.7% of all cancer fatalities. It is followed by colorectal and liver cancers, with death tolls of 904,000 and 759,000 respectively.
According to an assessment by Freddie Bray's team, about one-fifth of people worldwide will develop cancer during their lifetime, with approximately one-ninth of men and one-twelfth of women dying from the disease.
However, due to varying levels of development, cancer detection rates and survival rates can differ significantly between countries. For instance, in regions with very high Human Development Index (HDI) scores, one in twelve women will be diagnosed with breast cancer and one in seventy-one will die from it. In contrast, in areas with low HDI scores, breast cancer is diagnosed in one out of every twenty-seven women, but one in forty-eight will die from the disease.
What about the situation in China?
In China, lung cancer is the most prevalent cancer among both men and women.
The data on cancer in China provided by the International Agency for Research on Cancer (IARC) was developed in collaboration with China's National Cancer Center (NCC). The NCC has also released several studies, including an analysis of the cancer epidemiology in China for 2022.
For the year 2022, China estimated 4.825 million new cancer cases and 2.574 million cancer deaths, with lung cancer being the most common type.
In China, compared to the global average, lung cancer poses a more pronounced disease burden. Throughout 2022, the country saw a staggering 1.061 million new cases of lung cancer, equating to 75.1 individuals out of every 100,000 being diagnosed with the disease.
Simultaneously, lung cancer stands as the most "fatal" cancer in China. In 2022, 51.9 individuals per 100,000 succumbed to lung cancer. This high mortality rate is attributed to the often asymptomatic nature of early-stage lung cancer, which may progress to advanced stages before detection. Additionally, the prognosis for lung cancer is bleak; research indicates that from 2012 to 2015, the five-year survival rate for Chinese lung cancer patients was a mere 19.7%.
However, within the realm of lung cancer, the incidence and mortality rates for women are significantly lower than those for men.
Thyroid cancer and breast cancer are common health concerns for Chinese women, both linked to estrogen levels. Research has found a mutual increase in risk between these two cancers, with individuals who have either one being more susceptible to the other compared to the general population.
Fortunately, the mortality rates for breast cancer and thyroid cancer aren't very high. Throughout 2022, for every 100,000 Chinese women, there were 10.9 deaths from breast cancer and 1.1 from thyroid cancer. As early as between 2010 and 2014, the five-year survival rate for Chinese breast cancer patients had already reached 83.2%.
Among the top ten prevalent cancers in China, apart from cancers in the reproductive organs, both the incidence and mortality rates for other cancers are higher than the global average.
One striking observation is the lung cancer incidence rate among Chinese women, reaching 2.6 times the global average for females, despite a smoking rate of only 1.85%, which is lower than in many countries worldwide. Researchers speculate that the high incidence of lung cancer in women is partly due to outdoor air pollution and indoor air pollution from solid fuel combustion for heating and cooking.
Furthermore, there are variations in the types of cancer that people need to be especially cautious about depending on the region they live in.
The National Cancer Center analyzed the distribution of cancer incidence rates in different provinces of China in 2018, as outlined in the "Analysis of Malignant Tumor Epidemic Situation in China in 2022." They found that nasopharyngeal cancer is more prevalent in Guangdong, Guangxi, Hainan, Hunan, and Jiangxi, while renal cancer is relatively higher in northern regions, and prostate cancer is more prevalent in economically developed provinces.
Is it an illusion that more people are getting cancer?
Keen readers may notice that the incidence rates of some cancers among Chinese residents in 2022 have increased significantly compared to previous years. For instance, the crude incidence rate of thyroid cancer was 13.9 per 100,000 people in 2017, but by 2022, it surged to 33.0, more than doubling.
The National Cancer Center cautioned in a study that the increasing detection rates of cancer are indeed due to heightened cancer awareness and more proactive medical consultations. However, one statistical factor that cannot be ignored is that previous cancer data from the International Agency for Research on Cancer (IARC) was based on information from some cancer registries in China, unlike in 2022, where data was derived from 2806 county-level cancer registries across China. Therefore, the disparity between the 2022 Chinese cancer data and previous data from IARC may not accurately reflect changes in cancer incidence in China.
So, is the cancer incidence rate among Chinese residents increasing?
Researchers analyzed the changes in cancer incidence and mortality rates in China from 2000 to 2018 based on continuous tracking data from 22 cancer registries nationwide, thereby eliminating the impact of changes in data sources.
Their analysis concluded that over the past 20 years, the incidence of cancer in China has been increasing while the mortality rate has been decreasing. When broken down by gender, there's a significant increase in cancer incidence among women, while the trend remains stable among men.
In 2022, over half of the new thyroid cancer cases worldwide were reported in China, marking a significant annual increase among both Chinese men and women. From 2000 to 2018, the incidence rates rose by 16.9% and 15.7% respectively each year.
However, thyroid cancer is not daunting; it is an indolent, asymptomatic tumor. Its rapid increase in recent years is mainly due to heightened cancer prevention awareness, better healthcare opportunities, and the widespread availability of diagnostic technologies.
Meanwhile, in China, the incidence and mortality rates of cancers with poor prognosis, such as liver, stomach, and esophageal cancer, are continuously decreasing. At the same time, some cancers previously rare in China but common in developed countries, such as colorectal, prostate, and breast cancers, are showing a steady increase.
What can we do about cancer risk?
According to the International Agency for Research on Cancer, by 2050, the global number of new cancer cases is expected to reach 35 million, a 77% increase from the nearly 20 million cases in 2022. As the population ages, China’s cancer burden is also expected to grow.
For the general public, how can we reduce the risk of cancer in everyday life? The International Agency for Research on Cancer suggests that tobacco, obesity, and infections from bacteria and viruses are the three major risk factors for cancer. Therefore, controlling smoking and alcohol consumption, increasing daily exercise to manage weight, and practicing other preventative measures are effective strategies against many common cancers. The National Cancer Center of China has also stated that one-fourth of cancer deaths in China are related to smoking.
In addition, vaccinations and regular health check-ups are crucial. Vaccinations against Hepatitis B and HPV can effectively help us prevent liver cancer and cervical cancer. Colorectal and cervical cancers can be addressed through routine screenings, and if detected and treated early, the survival rates are very high.
Overall, the better our living conditions, the higher our chances of dealing with cancer become. Associate Professor Zheng Rongshou from the National Cancer Center and his team calculated that in 2020, the lifetime risk of developing cancer was 25.0% globally, 28.9% for the Chinese population, and nearly 50% in some developed countries like Japan and the UK. Therefore, take action! Nothing is more important than good health.
