Two important reports regarding cancer incidence in the United States¹ and globally² have been recently released. In summary, almost 20 million people worldwide were diagnosed with cancer in 2022, and almost 10 million died of their disease.² Lung cancer is the most common cancer globally, followed by female breast, colorectal, prostate, and stomach cancers. For women, breast cancer is the most common and is most often fatal; whereas, for men, the most common is lung cancer.² Cancer statistics from the United States released late last year indicated an alarming trend which was not covered in the global statistics: that colorectal and cervical cancers are increasing among individuals younger than 50 years and that colorectal cancer is now the first cause of cancer death among men and the second cause among women in this age group.¹ This is not an observation restricted to the United States; although the data are not as robust, increases in young-onset colorectal cancer have been documented from Chennai (India) to Korea.³ Siegel et al. reported that, for three countries in Europe (Netherlands, Cyprus, and Norway), the increase in colorectal cancer incidence was twice as rapid as that in older adults.³ Still, data are sparse when it comes to the Middle East and North African nations.

Recent reports from the United Arab Emirates (UAE) demonstrate that the issue is indeed global. The UAE National Cancer Registry (UAE-NCR) records cancer incidence rates stratified by age, sex, nationality (Emirati citizens vs. non-Emirati residents), and primary cancer site. The latest report published in February 2024 included all malignant and in-situ cases diagnosed in the UAE during the year 2021.⁴ Data were collected by registry staff at the Ministry of Health and Prevention and through focal points from stakeholders across the UAE (Department of Health Abu Dhabi central cancer registry, Dubai Health Authority central cancer registry, public and private hospitals [using codes from the International Classification of Diseases, Tenth Revision and International Classification of Diseases for Oncology], medical professionals, and pathology laboratories) through a standardized form and according to recommendations of the International Agency for Research on Cancer.⁴

Although the incidence rate for the most common cancers in the UAE are at or below global averages in countries with a high/very high Human Development Index, and although the age-specific incidence rates follow predicted trends and increase with advancing age across most cancers, a notable clustering of colorectal cancer incidence at early ages is similarly observed in the latest 2021 UAE-NCR report, which is consistent with available reports since 2014 from the same national registry.⁴ For instance, in total, 82 of 532 colorectal cancers (15.4%; 13.1% in Emiratis vs. 16.3% in non-Emiratis) occurred in patients younger than 40 years, whereas 107 colorectal cancers (20.1%: 8.1% in Emiratis vs. 25.2% in non-Emiratis) occurred in patients between ages 40 and 49 years.⁴

It is alarming to note that our population, although mixed between Emiratis and non-Emiratis, reflects other concerning trends among young people (Table 1).⁴ In the UAE, 25.4% of all cancer cases were diagnosed in patients younger than 40 years, with a similar range of 20%–30% observed across both men and women and in Emirati and non-Emirati patients. The peak frequency of cancer cases was in the group aged 40–44 years in the overall population and in both Emirati and non-Emirati women, whereas the peak was in a younger age group in non-Emirati men (aged 55–59 years) compared with Emirati men (aged 70–74 years).⁴ In total, 236 of 1139 breast cancers (20.7%: 17.4% in Emiratis vs. 21.5% in non-Emiratis) occurred in patients younger than 40 years, whereas 407 breast cancers (35.7%; 25.2% in Emiratis vs. 38.2% in non-Emiratis) occurred in patients between ages 40 and 49 years.⁴ By comparison, only 4% of breast cancers in the United States occurred in patients younger than 40 years, and 13% occurred in patients between ages 40 and 49 years.⁵ Similarly, in total, 293 of 595 thyroid cancers (49.2%; 50.3% in Emiratis vs. 48.8% in non-Emiratis) occurred in patients younger than 40 years, whereas 169 (28.4%; 25.9% in Emiratis vs. 29.6% in non-Emiratis) occurred in patients between ages 40 and 49 years.⁴

This may be primarily attributed to the UAE being a young nation populated mostly by expatriate, young residents. The median age of the UAE population, according to 2021 data, was approximately 30 years overall.⁶ In fact, the age-specific incidence rates for breast cancer among women illustrated in the 2021 UAE-NCR report are comparable to those reported in the United States; they rise steadily from age 25 years, cross the 100 per 100,000 threshold between ages 40 and 49, and peak at ages 70–74 years.^{4, 5} Therefore, one cannot assume an increased risk of developing cancer in young individuals in the UAE compared with other countries but, rather, a higher percentage of cancer cases in this age group. Nonetheless, and looking at the absolute rather than the relative risk, having such a high burden of cancer in younger age groups stresses the need for understanding risk factors for early onset disease that can inform optimal (early) screening and preventive strategies.^{7, 8}

The prevalence of obesity and overweight in the UAE youth is high, similar to other Arab countries facing increased consumption of unhealthy diets with poor nutritional benefits. Obesity and smoking (including all forms) have been prioritized on the UAE public health agenda, with multiple initiatives to control them. Several efforts to optimize the uptake of gender-neutral human papillomavirus vaccination and to mandate hepatitis B vaccination in high-risk groups have also been launched in the past 2 decades.⁷ Further research into the roles of other risk factors, such as the unique genetic admixture in a country highly populated by expatriates, cultural habits, environmental risks, and the microbiome, are called for to shed better light on cancer epidemiology in the UAE, and various projects have been recently launched with this objective, including the Emirati Genome Program.

The study of cancer incidence in young individuals must be global, with contributions from various nations and regions, so all can benefit from research outcomes with potential impact on screening guidelines and policy.

最近发布了两份关于美国¹和全球²癌症发病率的重要报告。总之，到 2022 年，全球将有近 2000 万人被诊断出患有癌症，近 1000 万人死于癌症。 ²肺癌是全球最常见的癌症，其次是女性乳腺癌、结直肠癌、前列腺癌和胃癌。对于女性来说，乳腺癌是最常见的，而且通常是致命的。而对于男性来说，最常见的是肺癌。 ²美国去年底发布的癌症统计数据显示出全球统计数据中未涵盖的令人震惊的趋势：50岁以下人群中结直肠癌和宫颈癌呈上升趋势，结直肠癌现已成为全球癌症死亡的首位原因。在这个年龄段中，男性是第二个原因，而女性则是第二个原因。 ¹这并非仅限于美国的观察；尽管数据并不那么可靠，但从印度钦奈到韩国，年轻发病的结直肠癌的发病率有所增加。 ³西格尔等人。报道称，欧洲三个国家（荷兰、塞浦路斯和挪威）的结直肠癌发病率增长速度是老年人的两倍。 ³尽管如此，中东和北非国家的数据仍然很少。

阿拉伯联合酋长国（UAE）最近的报告表明，这个问题确实是全球性的。阿联酋国家癌症登记处 (UAE-NCR) 记录了按年龄、性别、国籍（阿联酋公民与非阿联酋居民）和原发癌症部位分层的癌症发病率。 2024 年 2 月发布的最新报告涵盖了 2021 年阿联酋诊断的所有恶性病例和原位病例。4^数据由卫生和预防部的登记人员以及阿联酋各地利益相关者的联络点收集。健康阿布扎比中央癌症登记处、迪拜卫生局中央癌症登记处、公立和私立医院[使用《国际疾病分类》第十版修订版和《国际肿瘤疾病分类》代码]、医疗专业人员和病理学实验室）通过标准化表格并根据国际癌症研究机构的建议。 ⁴

尽管阿联酋最常见癌症的发病率等于或低于人类发展指数高/极高的国家的全球平均水平，并且尽管大多数癌症的特定年龄发病率遵循预测趋势并随着年龄的增长而增加，最新的 2021 年 UAE-NCR 报告中也观察到了早期结直肠癌发病率的显着聚集，该报告与 2014 年以来同一国家登记处的现有报告一致。 ⁴例如，总共 532 例结直肠癌中有 82 例（阿联酋为 15.4%；阿联酋为 13.1%，非阿联酋为 16.3%）发生在 40 岁以下的患者中，而 107 例结直肠癌（阿联酋为 20.1%；阿联酋为 8.1%，非阿联酋为 16.3%）发生在 40 岁以下的患者中。 25.2%（非阿联酋人）发生在 40 岁至 49 岁之间的患者中。 ⁴

令人震惊的是，我们的人口虽然是阿联酋人和非阿联酋人的混合体，但也反映出年轻人中其他令人担忧的趋势（表 1）。 ⁴在阿联酋，所有癌症病例中有 25.4% 是在 40 岁以下的患者中诊断出来的，男性和女性以及阿联酋人和非阿联酋患者的相似范围为 20%–30%。癌症病例的峰值频率出现在总人口中 40-44 岁的群体以及阿联酋和非阿联酋女性中，而峰值发生在非阿联酋男性的较年轻年龄组（55-59 岁）与阿联酋男性（70-74 岁）相比。 ⁴总共 1139 例乳腺癌中，有 236 例（阿联酋人为 20.7%；阿联酋人为 17.4%，非阿联酋人为 21.5%）发生在 40 岁以下的患者中，而 407 例乳腺癌（阿联酋人为 35.7%；阿联酋人为 25.2%，非阿联酋人为 38.2%） （非阿联酋人）发生在 40 岁至 49 岁之间的患者中。 ⁴相比之下，美国只有 4% 的乳腺癌发生在 40 岁以下的患者中，13% 的乳腺癌发生在 40 岁至 49 岁之间的患者中。 ⁵同样，总共 595 例甲状腺癌中有 293 例（阿联酋人为 49.2%；阿联酋人为 50.3%，非阿联酋人为 48.8%）发生在 40 岁以下的患者中，而 169 例（阿联酋人为 28.4%；阿联酋人为 25.9%，非阿联酋人为 29.6%） （非阿联酋人）发生在 40 岁至 49 岁之间的患者中。 ⁴

这可能主要归因于阿联酋是一个年轻的国家，人口主要为外籍年轻居民。根据 2021 年的数据，阿联酋人口的中位年龄总体约为 30 岁。 ⁶事实上，2021 年 UAE-NCR 报告中显示的女性乳腺癌特定年龄发病率与美国报告的数据相当；他们从 25 岁开始稳步上升，在 40 至 49 岁之间突破每 10 万人中 100 人的门槛，并在 70 至 74 岁达到顶峰。 ^{4, 5}因此，与其他国家相比，我们不能认为阿联酋年轻人患癌症的风险更高，而是认为该年龄组的癌症病例比例更高。尽管如此，从绝对风险而不是相对风险来看，年轻群体中癌症负担如此之高，强调需要了解早发疾病的风险因素，以便为最佳（早期）筛查和预防策略提供信息。 ^{7, 8}

阿联酋年轻人肥胖和超重的患病率很高，这与其他阿拉伯国家类似，也面临着营养不良的不健康饮食消费增加的问题。肥胖和吸烟（包括所有形式）已成为阿联酋公共卫生议程的优先事项，并采取了多项措施来控制它们。过去 20 年来，还开展了多项努力，以优化不分性别的人乳头瘤病毒疫苗接种，并强制高危人群接种乙型肝炎疫苗。 ⁷需要进一步研究其他风险因素的作用，例如外籍人口众多的国家的独特遗传混合物、文化习惯、环境风险和微生物组，以更好地了解阿联酋的癌症流行病学，并最近为此目标启动了各种项目，包括阿联酋基因组计划。

对年轻人癌症发病率的研究必须是全球性的，需要来自不同国家和地区的贡献，这样所有人都可以从对筛查指南和政策产生潜在影响的研究成果中受益。