About 1 in 8 cancer cases worldwide are tied to these infections — most of them preventable

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Millions of new cancer cases around the world may be caused by infections that are either treatable or preventable, suggesting that the cancer could have been avoided altogether.

That’s according to new research published in the journal The Lancet Oncology , which found that roughly 1 in 8 cancer cases around the world may be linked to infections – many of which can be prevented through vaccines, screening or relatively straightforward treatments.

“We can intervene before it gets anywhere near cancer,” said Gary Clifford, the study’s senior author and an epidemiologist at the International Agency for Research on Cancer.

“We just need the politics and the finances and the buy-in from the public and the communication to get the programs implemented. Prevention works,” Clifford said. “It’s an awareness-raising issue.”

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About 2.3 million new cancer cases were attributable to infections globally in 2024, which is equivalent to 12% of all cancer diagnoses, the new study found. And two infections stood out in particular: Helicobacter pylori, commonly known as H. pylori, which was mostly associated with gastric cancers and human papillomavirus, or HPV, which was predominantly associated with cervical cancer. Together, researchers estimate that these two infections accounted for more than 1.5 million cancer cases in 2024.

Other infections contributed substantially as well:

Hepatitis B or HBV was linked to an estimated 360,000 cancer cases, which were mostly liver cancers.

The Epstein-Barr virus or EBV was associated with about 260,000 cancer cases, of which a head and neck cancer starting in the nasopharynx was the main driver.

Hepatitis C or HCV was tied to 160,000 cancer cases, mostly liver cancers.

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“Some infection-related cancers, such as liver and gastric cancer, generally have poor prognosis, meaning that a similar proportion of deaths from these cancers are likely attributable to infection. For other cancers, including cervical cancer and Kaposi sarcoma, infection is necessary for cancer development,” Harriet Rumgay, epidemiologist at the International Agency for Research on Cancer and an author of the study, said in an email.

“However, highly effective prevention measures already exist for four of the five leading infectious causes of cancer, as well as for HIV,” Rumgay said, referring to the human immunodeficiency virus. The four infections include HPV and hepatitis B, for which vaccines are available, as well as H. pylori and hepatitis C, for which testing and treatments are available.

Clifford, Rumgay and their colleagues analyzed data from the Global Cancer Observatory’s Cancer Today database to estimate the incidence of cancer around the world in 2024. They examined how many of those cancer cases could be attributable to infections and then analyzed each infection-cancer pair in their data set.

The new analysis builds on earlier work published in 2018 , but the researchers now have a better understanding of the relationships between certain infections and cancer. The new study incorporated 16 additional infection-cancer pairs compared with the previous 2018 global analysis, including some cancers paired with EBV.

“EBV is one of these agents for which we knew it was related to some cancers. In fact, EBV was the first ever cancer-causing agent of infection to be discovered in Burkitt lymphoma,” Clifford said.

“That was like 60 years ago almost, and that was the first realization that a virus could cause cancer. And since then, we’ve identified it in other cancers, particularly nasopharyngeal carcinomas,” he said. “We were already clear about the link with EBV, even back in that 2018 data. So, it was there, but it wasn’t really fully addressed because we didn’t understand the full extent of the cancer burden that it was causing.”

The new research also reveals that the burden of infection-related cancers isn’t evenly distributed around the world. Low-income and middle-income countries accounted for 77% of all infection-attributable cancer cases, reflecting differences in the prevalence of cancer-causing infections as well as access to vaccines, screening, testing and treatment.

But if health officials know which infections are contributing to cancer, and where those infections are most common, they can focus resources on the strategies that have the potential to save lives.

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“Even within the United States, the burden of infection-related cancer is not evenly distributed, and some populations have higher rates of infections such as hepatitis B, hepatitis C, HPV or H. pylori, while others have less access to vaccination, screening or treatment. And these differences can translate into disparities in cancer incidence many years later,” said Veronika Fedirko, professor of epidemiology at The University of Texas MD Anderson Cancer Center in Houston, who was not involved in the new study.

“Infection-related cancers are certainly an important issue in the United States,” she said, referring to a separate analysis from the American Cancer Society that found in 2019, 3.4% of all cancers among adults 30 and older – which was about 60,310 cases – were attributable to seven infections evaluated: EBV, H. pylori, hepatitis B, hepatitis C, Kaposi sarcoma-associated herpesvirus, HIV and, the largest contributor, HPV.

“Having a cancer-causing infection does not mean that a person will develop cancer. These infections increase the risk of certain cancers, but most people who are infected will never develop cancer,” Fedirko said. “Cancer usually develops only in a small proportion of people, often when an infection persists for many years and together with other factors such as age, immune function, smoking, genetics or other exposures.”

Cancer is an enormously complicated group of diseases with many different causes and risk factors, including genetics, environmental exposures, aging and lifestyle factors. But the new findings show that infections represent an area where prevention can make a meaningful difference.

Prevention efforts can include vaccination and, when appropriate, testing for and treating infections that increase cancer risk. For some cancers, screening can also identify precancerous changes so they can be treated before invasive cancer develops.

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Getting tested and following up with a doctor “almost takes away any cancer risk,” Clifford said.

Once infections get diagnosed, “we know how to manage them,” he said. “The large majority of these infections will not cause cancer. Some of them will, and we’re learning more about which ones, but that’s a work in progress. The point is: It doesn’t mean that you’ve got a cancer just because you have the infection.”

For instance, people can be screened for hepatitis C and treated if they are infected, thus helping to prevent cancer from developing down the road.

The same is true for H. pylori. The bacterium is relatively common, and many people who carry it may not immediately realize they have an infection. But H. pylori can cause chronic inflammation in the stomach and become a major risk factor for stomach cancer. Treating the infection with antibiotics can reduce that risk, giving doctors another opportunity to intervene before cancer may develop.

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Additionally, HPV and hepatitis B are examples of how vaccination can help prevent cancer. Hepatitis B infection can damage the liver over time and increase the risk of liver cancer, but there is a vaccine available that can help prevent the viral infection.

HPV is a group of more than 200 related viruses , which can spread through sexual contact. In some cases, HPV infection can lead to six types of cancer : cervical, anal, penile, vaginal, vulvar and oropharyngeal (mouth and throat). But the vaccine can protect against those cancers since it works by preventing HPV infection.

The new research “teaches us the importance of vaccination and how that can prevent different types of cancer,” Dr. Nancy Lee, a radiation oncologist at Memorial Sloan Kettering Cancer Center who was not involved in the new study, said in an email.

“This is no different than getting your flu shot to prevent the flu. The public needs to be made aware and vaccination should be reinforced,” Lee said. “Many different types of cancers are caused by infection and if we prevent the infection, the incidence of cancer should be lower.”

Other prevention measures that reduce transmission of various cancer-attributable infections include “safe injection practices, condom use, and HIV pre-exposure prophylaxis,” Rumgay said. “If implemented widely and equitably, these strategies could prevent hundreds of thousands, if not millions, of future cancer cases worldwide.”

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全球数百万新增癌症病例可能是由可治疗或可预防的感染引起的，这意味着癌症原本是可以完全避免的。

根据发表在《柳叶刀肿瘤学》杂志上的一项新研究，全球大约八分之一的癌症病例可能与感染有关——其中许多感染可以通过疫苗、筛查或相对简单的治疗方法来预防。

“我们可以在它发展成癌症之前进行干预，”该研究的资深作者、国际癌症研究机构的流行病学家加里·克利福德说。

“我们只需要政治支持、资金保障、公众支持和有效的沟通，就能让这些项目得以实施。预防才是关键，”克利福德说。“这关乎提高公众意识。”

简单的血液检查就能检测出50多种癌症。这其中的复杂之处就在于此。

一项新研究发现，2024年全球约有230万例新增癌症病例可归因于感染，相当于所有癌症诊断病例的12%。其中两种感染尤为突出：幽门螺杆菌（Helicobacter pylori，简称H. pylori），主要与胃癌相关；以及人乳头瘤病毒（HPV），主要与宫颈癌相关。研究人员估计，这两种感染加起来在2024年导致了超过150万例癌症病例。

其他感染也造成了相当大的影响：

据估计，乙型肝炎（HBV）与 36 万例癌症病例有关，其中大部分是肝癌。

爱泼斯坦-巴尔病毒（EBV）与大约 26 万例癌症病例有关，其中以鼻咽部开始的头颈癌是主要原因。

丙型肝炎（HCV）与 16 万例癌症病例有关，其中大部分是肝癌。

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“一些与感染相关的癌症，例如肝癌和胃癌，预后通常较差，这意味着这些癌症死亡病例中，有相当一部分可能归因于感染。而对于其他癌症，包括宫颈癌和卡波西肉瘤，感染则是癌症发展的必要条件，”国际癌症研究机构的流行病学家、该研究的作者之一哈里特·鲁姆盖在电子邮件中表示。

“然而，对于五大主要致癌传染病中的四种以及艾滋病毒，目前已经存在高效的预防措施，”鲁姆盖说道。他指的是人类免疫缺陷病毒（HIV）。这四种传染病包括人乳头瘤病毒（HPV）和乙型肝炎（已有疫苗），以及幽门螺杆菌和丙型肝炎（已有检测和治疗方法）。

克利福德、拉姆盖及其同事分析了全球癌症观察站的“今日癌症”数据库中的数据，以估算 2024 年全球癌症的发病率。他们研究了其中有多少癌症病例可归因于感染，然后分析了数据集中的每一对感染-癌症病例。

这项新分析建立在2018年发表的早期研究之上，但研究人员现在对某些感染与癌症之间的关系有了更深入的了解。与2018年的全球分析相比，这项新研究纳入了16个额外的感染-癌症组合，其中包括一些与EB病毒相关的癌症。

“EBV是已知与某些癌症相关的病原体之一。事实上，EBV是第一个在伯基特淋巴瘤中发现的致癌感染因子，”克利福德说。

“那差不多是60年前的事了，那是我们第一次意识到病毒可能致癌。从那以后，我们又在其他癌症中发现了这种病毒，尤其是鼻咽癌，”他说道。“早在2018年的数据中，我们就已经清楚地认识到它与EB病毒的关联。所以，病毒一直存在，但当时并没有得到充分重视，因为我们并不完全了解它造成的癌症负担有多大。”

这项新研究还揭示，感染相关癌症的负担在全球分布不均。低收入和中等收入国家占所有感染相关癌症病例的77%，这反映了致癌感染的流行程度以及疫苗、筛查、检测和治疗的可及性方面的差异。

但是，如果卫生官员知道哪些感染会导致癌症，以及这些感染在哪些地方最常见，他们就可以将资源集中用于有可能挽救生命的策略。

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HPV疫苗可以将某些癌症的发病率降低一半。专家解释了为什么男性和男孩应该接种该疫苗。

“即使在美国国内，感染相关癌症的负担分布也不均衡，一些人群感染乙型肝炎、丙型肝炎、人乳头瘤病毒（HPV）或幽门螺杆菌等疾病的比例较高，而另一些人群则较少有机会获得疫苗接种、筛查或治疗。这些差异可能会在多年后转化为癌症发病率的差异，”德克萨斯大学MD安德森癌症中心流行病学教授维罗妮卡·费迪尔科（Veronika Fedirko）说道，她并未参与这项新研究。

“感染相关的癌症在美国无疑是一个重要问题，”她说道，并提及美国癌症协会的一项独立分析，该分析发现，2019 年，30 岁及以上成年人所有癌症病例中的 3.4%（约 60,310 例）是由评估的七种感染引起的：EBV、幽门螺杆菌、乙型肝炎、丙型肝炎、卡波西肉瘤相关疱疹病毒、HIV，以及最大的致病因素 HPV。

费迪尔科说：“感染致癌物并不意味着一定会患上癌症。这些感染会增加患某些癌症的风险，但大多数感染者终生都不会患上癌症。癌症通常只发生在少数人身上，而且往往是在感染持续多年，并与其他因素（例如年龄、免疫功能、吸烟、遗传或其他暴露）共同作用的情况下才会发生。”

癌症是一组极其复杂的疾病，其病因和风险因素众多，包括遗传、环境暴露、衰老和生活方式等。但新的研究结果表明，感染是预防可以发挥重要作用的领域。

预防措施包括接种疫苗，并在适当情况下检测和治疗会增加癌症风险的感染。对于某些癌症，筛查还可以识别癌前病变，以便在发展成侵袭性癌症之前进行治疗。

美国疾病控制与预防中心表示，所有成年人都应该至少接受一次乙型肝炎筛查。

克利福德说，接受检查并跟进医生“几乎可以消除任何患癌风险”。

他说：“一旦确诊感染，我们就知道如何治疗。绝大多数感染不会导致癌症。有些会，我们正在了解更多关于哪些感染会导致癌症的信息，但这方面的研究还在进行中。关键是：感染并不意味着你一定得了癌症。”

例如，可以对人们进行丙型肝炎筛查，如果感染了丙型肝炎，可以进行治疗，从而有助于预防将来患上癌症。

幽门螺杆菌的情况也是如此。这种细菌相对常见，许多携带者可能不会立即意识到自己已被感染。但幽门螺杆菌会导致胃部慢性炎症，并成为胃癌的主要危险因素。使用抗生素治疗感染可以降低这种风险，使医生有机会在癌症发生前进行干预。

英国研究发现，HPV疫苗可使女性宫颈癌发病率降低87%。

此外，HPV 和乙型肝炎都是疫苗接种如何帮助预防癌症的例子。乙型肝炎病毒感染会随着时间的推移损害肝脏并增加患肝癌的风险，但目前已有疫苗可以帮助预防这种病毒感染。

HPV是一组包含200多种相关病毒的病毒群，可通过性接触传播。在某些情况下，HPV感染可导致六种癌症：宫颈癌、肛门癌、阴茎癌、阴道癌、外阴癌和口咽癌（口腔和咽喉癌）。但疫苗可以预防这些癌症，因为它通过预防HPV感染发挥作用。

纪念斯隆-凯特琳癌症中心放射肿瘤学家南希·李博士（她并未参与这项新研究）在一封电子邮件中表示，这项新研究“告诉我们接种疫苗的重要性，以及疫苗如何预防不同类型的癌症”。

李说：“这和接种流感疫苗预防流感没什么区别。公众需要了解这一点，疫苗接种也应该得到加强。许多不同类型的癌症都是由感染引起的，如果我们能预防感染，癌症的发病率就会降低。”

鲁姆盖表示，其他可减少多种癌症相关感染传播的预防措施包括“安全注射、使用安全套和艾滋病毒暴露前预防”。“如果这些策略得到广泛且公平的实施，就能在全球范围内预防数十万甚至数百万例未来的癌症病例。”