A new report examining cancer in adolescents and young adults (AYAs, defined as diagnoses occurring between the ages of 15 and 39) provides updated estimates of the contemporary cancer burden in this age group, with predictions that 89,500 cases and 9,270 deaths will occur in this group in 2020 in the United States. The report was published by Miller et al in CA: A Cancer Journal for Clinicians.
AYAs with cancer are frequently grouped with older or younger patient populations and/or presented in aggregate, masking the wide heterogeneity in cancer occurrence within this population. To address this issue, American Cancer Society investigators also examined cancer incidence, survival, and mortality among AYAs by race/ethnicity and for smaller age groups (15–19 years, 20–29 years, and 30–39 years).
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Racial/Ethnic Group Rates of Incidence, Mortality
Cancer incidence rates among AYAs are highest in those who are non-Hispanic White (83 per 100,000 population during 2012–2016) and lowest in those who are Asian/Pacific Islander (54 per 100,000 population) for both sexes. This reflects higher rates in non-Hispanic White AYAs for thyroid cancer, testicular tumors, and melanoma compared with other major racial/ethnic groups. Unlike adults aged 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 noted that despite patterns in overall incidence, cancer mortality rates are highest in non-Hispanic Black AYAs, particularly women (12.6 per 100,000 vs 9.2 in non-Hispanic White persons), reflecting substantial survival disparities compared with those who are non-Hispanic White. The largest 5-year cancer-specific survival disparities occurred among those who are non-Hispanic Black compared with non-Hispanic White individuals for acute lymphocytic leukemia (57% vs 71%, respectively) and female breast cancer (78% vs 89%, respectively).
Incidence and Mortality Over Time
By age group, the cancer incidence rate in AYAs increased during the most recent decade (2007–2016) overall, but it 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 AYAs who are between the ages of 20 and 39 and 4% among AYAs who are between the ages of 15 and 19. Incidence increased for several cancers linked to obesity, including kidney (3% across all age groups), uterine corpus (3% in the 20–39 age group), and colorectal (0.9%–1.5% in the 20–39 age group).
In contrast to incidence, cancer mortality rates among AYAs for all cancers combined declined in the past decade (2008–2017) by 1% across sex and age groups, except in women between the ages of 30 and 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
Other highlights from the report include:
- Adolescents (aged 15–19) are more likely to be diagnosed with cancers associated with childhood, such as Hodgkin lymphoma, whereas those between the ages of 20 and 39 are more likely to be diagnosed with adult cancers, such as breast. Thyroid cancer is the only cancer predicted to rank among the three most commonly diagnosed cancers in each AYA age group in 2020.
- Leukemia continues to be the leading cause of cancer death in individuals between the ages of 15 and 29. Among those aged 30 to 39, breast (women) and colorectal (men) cancers are the leading cancer causes of death.
- Melanoma incidence rates during 2007 to 2016 rapidly declined in those aged 15 to 29 (4%–6% annually, on average). However, among those between the ages of 30 and 39 years, the rates declined only slightly among men and remained flat among women.
- Overall 5-year relative survival in AYAs for all cancers combined (83%–86% across age groups) is similar to that in children (84%), but it masks lower survival for several cancer types, such as acute lymphocytic leukemia (60% vs 91%, respectively).
The report noted 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 with childhood cancer survivors, AYAs have a higher risk of disease progression and death from the original cancer. Compared with older patients with cancer, 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 said 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 United States 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,” wrote the authors. “AYAs diagnosed with cancer also continue to face challenges in health-care access during early life transitions, which can negatively impact treatment.”
Disclosure: For full disclosures of the study authors, visit acsjournals.onlinelibrary.wiley.com.
