Rates of cancer increased by 30% from 1973 to 2015 in adolescents and young adults (AYAs) (persons aged 15–39 years) in the United States, according to a review of almost a half million cases in the National Institutes of Health’s Surveillance, Epidemiology, and End Results database.
There was an annual increase of 0.537 new cases per 100,000 people, from 57.2 cases per 100,000 in 1973 to 74.2 in 2015.
Kidney carcinoma led with the highest rate increase. There were also marked increases in thyroid and colorectal carcinoma, germ cell and trophoblastic neoplasms, and melanoma, among others.
The report was published online December 1 in JAMA Network Open.
“Clinicians should be on the lookout for these cancers in their adolescent and young adult patients,” said senior investigator Nicholas Zaorsky, MD, an assistant professor of radiation oncology and public health sciences at the Penn State Cancer Institute, Hershey, Pennsylvania.
“Now that there is a better understanding of the types of cancer that are prevalent and rising in this age group, prevention, screening, diagnosis and treatment protocols specifically targeted to this population should be developed,” he said in a press release.
The reasons for the increases are unclear, but environmental and dietary factors, increasing obesity, and changing screening practices are likely in play, the authors comment. In addition, “cancer screening and overdiagnosis are thought to account for much of the increasing rates of thyroid and kidney carcinoma, among others,” they add.
It’s important to note, however, that “this phenomenon is largely driven by trends for thyroid cancer, which is thought to be a result of overdiagnosis,” said ACS surveillance researcher Kimberly Miller, MPH, when asked to comment on the new study.
“As such, it is extremely important to also consider trends in cancer mortality rates among this age group, which are declining overall but are increasing for colorectal and uterine cancers. The fact that both incidence and mortality rates are increasing for these two cancers suggests a true increase in disease burden and certainly requires further attention and research,” she said.
Historically, management of cancer in AYAs has fallen somewhere between pediatric and adult oncology, neither of which capture the distinct biological, social, and economic needs of AYAs. Research has also focused on childhood and adult cancers, leaving cancer in AYAs inadequately studied.
The new findings are “valuable to guide more targeted research and interventions specifically to AYAs,” Zaorsky and colleagues say in their report.
Among female patients ― 59.1% of the study population ― incidence increased for 15 cancers, including kidney carcinoma (annual percent change [APC], 3.632), thyroid carcinoma (APC, 3.456), and myeloma, mast cell, and miscellaneous lymphoreticular neoplasms not otherwise specified (APC, 2.805). Rates of five cancers declined, led by astrocytoma not otherwise specified (APC, –3.369) and carcinoma of the gonads (APC, –1.743).
Among male patients, incidence increased for 14 cancers, including kidney carcinoma (APC, 3.572), unspecified soft tissue sarcoma (APC 2.543), and thyroid carcinoma (APC, 2.273). Incidence fell for seven, led by astrocytoma not otherwise specified (APC, –3.759) and carcinoma of the trachea, bronchus, and lung (APC, –2.635).
Increased testicular cancer rates (APC, 1.246) could be related to greater prenatal exposure to estrogen and progesterone or through dairy consumption; increasing survival of premature infants; and greater exposure to cannabis, among other possibilities, the investigators say.
Increases in colorectal cancer might be related to fewer vegetables and more fat and processed meat in the diet; lack of exercise; and increasing obesity. Human papillomavirus infection has also been implicated.
Higher rates of melanoma could be related to tanning bed use.
Declines in some cancers could be related to greater use of oral contraceptives; laws reducing exposure to benzene and other chemicals; and fewer people smoking.
Although kidney carcinoma has increased at the greatest rate, it’s uncommon. Colorectal and thyroid carcinoma, melanoma, non-Hodgkin lymphoma, and germ cell and trophoblastic neoplasms of the gonads contribute more to the overall increase in cancers among AYAs, the investigators note.
Almost 80% of the patients were White; 10.3% were Black.
The study was funded by the National Center for Advancing Translational Sciences. The investigators have disclosed no relevant financial relationships.
JAMA Netw Open. Published online December 1, 2020. Full text
M. Alexander Otto is a physician assistant with a master’s degree in medical science. He is an award-winning medical journalist who worked for several major news outlets before joining Medscape, including McClatchy and Bloomberg. He is an MIT Knight Science Journalism fellow. Email: [email protected].