越来越多的证据表明，50 岁以下成年人中诊断出的早发癌症的发病率惊人地增加，这些癌症发生在结直肠、食道、肝外胆管、胆囊、肝癌、胃癌、胰腺以及骨髓中（多发性骨髓瘤）、乳房、头颈、肾脏、前列腺、甲状腺和子宫体（子宫内膜）。虽然早发癌症研究涵盖了多种器官的研究，但本文重点关注消化系统癌症的研究。虽然消化系统中的少数早发癌症与易患癌症的高外显率种系遗传变异有关，但其中大多数癌症是散发性的和多因素的。尽管已经假设了饮食、生活方式、环境和微生物组从生命早期到成年（即在一个人的生命历程中）的潜在病因作用，但这些因素的确切贡献仍然不确定。饮食、生活方式和环境暴露已被证明会改变口腔和肠道微生物群。为了应对早发癌症的上升趋势，需要跨学科的研究方法，包括生命全程流行病学和分子病理流行病学框架、营养和环境科学、多组学技术等。我们回顾当前的证据并讨论新兴的研究机会，这可以提高我们对其病因的理解，并帮助我们设计更好的预防和治疗策略，以减轻人群的癌症负担。

Accumulating evidence indicates an alarming increase in the incidence of early-onset cancers, which are diagnosed among adults under 50 years of age, in the colorectum, esophagus, extrahepatic bile duct, gallbladder, liver, stomach, pancreas, as well as the bone marrow (multiple myeloma), breast, head and neck, kidney, prostate, thyroid, and uterine corpus (endometrium). While the early-onset cancer studies have encompassed research on the wide variety of organs, this article focuses on research on digestive system cancers. While a minority of early-onset cancers in the digestive system are associated with cancer-predisposing high penetrance germline genetic variants, the majority of those cancers are sporadic and multifactorial. Although potential etiological roles of diets, lifestyle, environment, and the microbiome from early life to adulthood (i.e. in one's life course) have been hypothesized, exact contribution of each of these factors remains uncertain. Diets, lifestyle patterns, and environmental exposures have been shown to alter the oral and intestinal microbiome. To address the rising trend of early-onset cancers, transdisciplinary research approaches including lifecourse epidemiology and molecular pathological epidemiology frameworks, nutritional and environmental sciences, multi-omics technologies, etc. are needed. We review current evidence and discuss emerging research opportunities, which can improve our understanding of their etiologies and help us design better strategies for prevention and treatment to reduce the cancer burden in populations.