WHO Projects Cancer Cases to Nearly Double by 2050 as Studies Link COVID-19 to Cancer Risk and Outcomes

Cancer cases worldwide are projected to nearly double by 2050, to 35 million from 19.5 million annually, according to a new report from the World Health Organization. At the same time, new research shows that severe COVID-19 infections may leave lasting changes in the lung that increase the risk of future lung cancer, and that pandemic-related disruptions to cancer care led to worsened 1-year survival and 17,390 excess cancer-related deaths in the United States.

One of the main reasons cases are soaring is that people are living longer. Screening and other forms of cancer detection are also becoming more commonplace. Even the fact a greater proportion of deaths are from cancer is the result of other health threats fading. Today, about 65 million deaths occur globally each year: about 14 million are owing to infectious diseases, while 43 million are because of non-communicable diseases (NCDs) such as cardiovascular disease, cancer, chronic obstructive pulmonary disease and diabetes. Seven of the top 10 causes of death in the world are now non-communicable diseases.

The dramatic drop in infectious disease deaths, particularly the "big three" — tuberculosis, malaria and HIV-AIDS — has allowed people in the developing world to live longer and develop conditions such as heart disease and cancer. Mortality from those diseases has fallen by two-thirds in this century.

The WHO report highlights growing inequities. In wealthy countries like Canada, the five-year survival rate after breast cancer diagnosis is 90 per cent; in lower-income countries it's less than 30 per cent. Twenty-three countries in the world don't even have radiation facilities, one of the most common cancer treatments. Two-thirds of the countries worldwide don't have universal health coverage. In some countries, 90 per cent of cancer patients abandon treatment because it's unaffordable. "Whether a person survives cancer should never depend on where they were born or what they earn," the WHO director-general said in response to the new report. "The inequities documented in this report are not inevitable; they are the consequence of choices."

About four in 10 cancer cases are related to four underlying causes: smoking, alcohol misuse, excess weight and infections. Vaccination against human papillomavirus has nearly eliminated cervical cancer in Western countries, while in sub-Saharan Africa it remains the number one cancer killer. Vaccination against hepatitis B prevents liver cancer, and treating helicobacter pylori bacterium with antibiotics has slashed rates of stomach cancer. The embrace of GLP-1 weight loss drugs in wealthy countries has the potential to dramatically reduce obesity-related cancer — a more than 40-per-cent drop, according to one study.

Separately, a report published June 24 by the American Association for Cancer Research describes the disparate burden of cancer across population groups in the United States. Black populations experience higher incidence and mortality for several cancers, including multiple myeloma and prostate cancer, than Whites, and American Indian and Alaska Natives have higher incidence and mortality for cancers of the colorectum, kidney, and cervix. A disproportionate burden of infection-related cancers, including liver and stomach cancers, is born by Hispanic and Asian populations. The overall cancer death rate remains higher among Black and American Indian/Alaska Native populations; there is a lower five-year relative cancer survival for all racial and ethnic minorities compared with White populations. A disproportionate burden of cancer is also seen among rural residents, those living in persistent-poverty areas, and sexual and gender minority populations. "These cancer disparities contribute to the high national cancer burden and slow the overall progress against cancer," the report's steering committee chair said in a statement.

A new study published in Cell suggests that severe viral pneumonia — including severe COVID-19 — may leave behind lasting changes in the lung that increase the risk of future lung cancer or accelerate tumor growth if cancer emerges. Researchers at Duke University analyzed large human health datasets and found that patients hospitalized with severe COVID-19 had about a 24 percent higher incidence of lung cancer diagnosis over the next four years. The study examined the Epic Cosmos database, including nearly 900,000 individuals hospitalized with severe COVID-19 and tens of millions of control subjects. In mouse models, tumors grew significantly faster in animals that had previously experienced severe viral infection. The researchers traced this effect to persistent changes in lung cells — an "epigenetic scar" — that altered how genes involved in inflammatory signaling were regulated. The lung accumulated high numbers of tumor-associated neutrophils, while cytotoxic CD8 T cells, which normally attack cancer cells, were reduced in both number and activity. Importantly, infection alone did not initiate cancer; instead, it acted as a cooperating factor that accelerates tumor progression when oncogenic mutations — such as KRAS mutations common in lung cancer — are already present. Blocking neutrophil recruitment through inhibition of the chemokine receptor CXCR2 reduced tumor growth in virus-experienced lungs, and when combined with immune checkpoint blockade targeting PD-L1, the treatment restored CD8 T cell activity and further suppressed tumor progression.

Another study, published in JAMA Network Oncology, examined 1-year cause-specific survival among patients diagnosed with cancer in 2020 and 2021 using Surveillance, Epidemiology, and End Results 21 Registries (SEER-21) data, which covers approximately 41.9% of the US population. During 2020 and 2021, 1,008,012 individuals were diagnosed with cancer in the United States. Compared with pre-pandemic trends, 1-year cause-specific survival declined significantly for both early- and late-stage cancers in 2020 and 2021, with larger reductions seen in late-stage disease. These survival declines were associated with an estimated 17,390 excess cancer-related deaths within 1 year of diagnosis during the first 2 years of the COVID-19 pandemic. The largest survival losses occurred among older adults, individuals of other non-Hispanic races and ethnicities, and in site-specific analyses for early-stage esophageal and colorectal cancers and late-stage prostate cancer. Patients diagnosed with cancer in 2020 and 2021 had worse short-term survival than those diagnosed from 2015 to 2016. "The most important takeaway for health systems from this study is the need to build health system resilience," the study's co-author said.