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Thyroid cancer drives increase in cancer incidence among adolescents and young adults

​Cancer mortality rates are highest in non-Hispanic Black AYAs, particularly females

A new ACS report examining cancer in adolescents and young adults (ages 15 to 39) provides updated estimates of the cancer burden in this age group, predicting that 89,500 cases and 9,270 deaths will occur in 2020 in the U.S. The report appears in the American Cancer Society journal CA: A Cancer Journal for Clinicians, and was co-written by ACS researchers Kim Miller, MPH, Rebecca Siegel, MPH, and others. 

To watch a slideshow of key findings, visit cancer.org.

The most common types of adolescents and young adults (AYAs) cancers vary substantially by age

AYAs with cancer are frequently grouped with older or younger patient populations and/or presented in aggregate, masking the wide difference in cancer occurrence within this population. To address this issue, ACS investigators also examined cancer incidence, survival, and mortality among AYAs by race/ethnicity and for smaller age groups (15-19, 20-29, and 30-39). 

The bar graph above shows the difference in the most commonly diagnosed cancers by age group:

  • Ages 15 to 19: The 3 most common types are thyroid cancer, Hodgkin lymphoma, and brain tumors. Teens have a higher proportion of childhood cancers compared to the older age groups. 
  • Ages 20 to 29: The most common are thyroid cancer, testicular cancer, and melanoma. 
  • Ages 30 to 39: The most common are breast cancer (in females), thyroid cancer, and melanoma.

Among these cancers, incidence rates are highest in non-Hispanic whites and lowest in Asian/Pacific Islanders (83 vs 54 per 100,000 people) for both sexes. This reflects higher rates in non-Hispanic white AYAs for thyroid cancer, testicular tumors, and melanoma compared to other major racial/ethnic groups. Unlike adults ages 40 and older, however, female breast cancer incidence rates in non-Hispanic Black AYAs are 14% higher than those in non-Hispanic white AYAs (25.9 vs 22.3 per 100,000 population). 

The authors also note that despite patterns in overall incidence, cancer mortality rates are highest in non-Hispanic Black AYAs, particularly females (12.6 per 100,000 vs 9.2 in non-Hispanic white persons), reflecting substantial survival disparities compared to those who are non-Hispanic white. The largest 5-year cancer-specific survival disparities occur among those who are non-Hispanic Black compared with non-Hispanic whites for acute lymphocytic leukemia (57% vs 71%, respectively) and female breast cancer (78% vs 89%, respectively).

Thyroid cancer diagnoses have driven the overall increase in incidence rates—especially for women

Overall, the researchers found that cancer incidence rates increased across all 3 age groups during the past decade. Notably, thyroid cancer was the only common type among each age group’s top 3 types of cancer. Thyroid cancer incidence rates among women in their 20s are 5 times greater than those in men (15 women vs 3 men per 100,000 people).

By age group, the cancer incidence rate in AYAs increased during the most recent decade (2007-2016) overall but showed signs of stabilizing among men in their 20s. The rise is largely driven by thyroid cancer incidence rates, which rose by approximately 3% annually among those aged 20 to 39 and 4% among those aged 15 to 19 years. Incidence increased for several cancers linked to obesity, including kidney (3% across all age groups), uterine corpus (3% in group aged 20-39 years), and colorectum (0.9%-1.5% in the group aged 20-39 years).  

In contrast to incidence, cancer mortality rates among AYAs for all cancers combined declined in the past decade (2008 through 2017) by 1% across sex and age groups except females aged 30 to 39, among whom rates remained stable due to a flattening of declines in breast cancer mortality. Mirroring incidence, mortality rates increased during the most recent 10 data years (2008-2017) for colorectal and uterine corpus cancers.

Other highlights from the report include:

  • Cancer incidence rates for all types combined are similar for males and females ages 15 to 19. However, 20- to 29-year-old women have rates that are 30% higher than for men of the same age (55 women vs 42 men per 100,000 people). The incidence rate is nearly double in 30- to 39-year-olds (161 women vs 84 men per 100,000 people.) These differences are mainly because of the higher incidence of breast cancer, melanoma, and thyroid cancer in women.
  • Adolescents (aged 15-19 years) are more likely to be diagnosed with cancers associated with childhood, such as Hodgkin lymphoma, while those aged 20 to 39 years are more likely to be diagnosed with adult cancers, such as breast. 
  • Leukemia continues to be the leading cause of cancer death in ages 15 to 29 years. Among ages 30-39 years, breast (women) and colorectal (men) cancers are the leading cancer causes of death.
  • Melanoma incidence rates during 2007-2016 rapidly declined in ages 15 to 29 (4%-6% annually, on average). However, among ages 30-39 years, rates declined only slightly among men and remained flat among women. 
  • The most commonly diagnosed cancer for males aged 20 to 39 is testicular cancer. The incidence rates per 100,000 people are: 13 for non-Hispanic white men;10 for both Hispanic men and American Indians/Alaskan Natives;2.4 for non-Hispanic Black men.
  • Overall 5-year relative survival in AYAs for all cancers combined (83%-86% across age groups) is similar to that in children (84%), but masks lower survival for several cancer types, such as acute lymphocytic leukemia (ALL; 60% vs 91%, respectively).

The report notes an increasing body of evidence that tumors in AYAs are molecularly distinct from those in younger or older populations, suggesting differences in etiology and in treatment options. In addition, studies have shown that compared to childhood cancer survivors, AYAs have a higher risk of progression and death from their original cancer. Compared to older cancer patients, AYAs have a higher risk of long-term and late effects including infertility, sexual dysfunction, cardiovascular disease, and other future cancers. However, further research in these areas is needed. 

The authors say that progress in reducing cancer morbidity and mortality among AYAs could be improved with more equitable access to health care, as AYAs are more likely than other age groups in the U.S. to be uninsured. Increased clinical trial enrollment, expanded research, and improved awareness among clinicians and patients of early symptoms and signs of cancer could also accelerate progress. 

“Although there has been rapid progress in the scientific understanding of cancer in AYAs over the last decade, several research gaps in etiology, basic biology, treatment, and survivorship remain,” write the authors. “AYAs diagnosed with cancer also continue to face challenges in health care access during early life transitions, which can negatively impact treatment.”


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