Scientists have known for a long time that childhood cancers are not the same as adult cancers. The number of cases, the biology of the tumors, the treatments needed, and the survival rates are all different. More recently, researchers have recognized that cancers in adolescents and young adults (AYAs) are also distinct.
Cancers in this group, which covers ages 15 to 39, are the focus of a new report published in CA: A Cancer Journal for Clinicians on September 17, 2020. “Cancer Statistics for Adolescents and Young Adults, 2020" was co-written by American Cancer Society (ACS) researchers Kim Miller, MPH, Rebecca Siegel, MPH, and others. The AYA statistics were overviewed earlier this year in the special section of Cancer Facts & Figures, 2020.
The report details the cancer incidence and mortality rates in AYAs, which describe the frequency with which new cases and deaths occur in a given population. The researchers looked at rates and trends by sex and race/ethnicity, across 3 smaller age groups:
In the report, ACS researchers estimate that in 2020, there will be approximately 89,500 new cancer cases and 9,270 deaths from cancer in AYAs. Cancer incidence rates are highest in non-Hispanic Whites and lowest in Asian/Pacific Islanders (83 vs 54 per 100,000 people). However, mortality rates for all cancers combined are highest in non-Hispanic Black AYAs despite having 25% lower incidence rates than non-Hispanic White AYAs.
This bar graph shows the difference in the most commonly diagnosed cancers by age group.
The number of diagnoses for all these cancers increases with age, except for Hodgkin lymphoma, acute lymphocytic leukemia (ALL), and bone tumors, which are more common in teens.
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). The rising rates of diagnosis are largely due to increases in medical imaging tests that have detected more cancers—but studies show the increasing trend may reflect a true rise in the diagnosis of advanced-stage thyroid cancer.
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.)
The differences between the sexes are mainly because of the higher incidence of breast cancer, melanoma, and thyroid cancer in women.
The most commonly diagnosed cancer for males aged 20 to 39 is testicular cancer. These are the incidence rates by race, from high to low.
The overall increase in breast cancer incidence rates in AYAs in recent years is driven largely by non-Hispanic White women, for whom rates have increased since at least 1995. The fact that women are having fewer children and are older when they first give birth may be contributing to this.
Incidence rates in non-Hispanic Black AYAs are 14% higher than in non-Hispanic White AYAs, whereas in older women, rates are highest in Whites. However, the higher incidence rates in Black AYA women are confined to hormone receptor-negative breast cancer. In particular, the incidence rate for triple-negative breast cancer is 50% higher in Black AYAs than in White AYAs.
Compared to older women diagnosed with breast cancer, AYA women are more likely to be diagnosed when the cancer is already at an advanced stage. Less than 50% of AYAs are diagnosed while the cancer is still at a local stage (just in the breast), compared to 60% in 45- to 54-year-olds and 65% in those ages 55 to 64.
Most of these differences are likely due to cancer screening guidelines by age. For example, breast cancer screening, which can often detect cancers at an earlier stage, isn’t recommended until at least age 40 for most women. Likewise, screening for colorectal cancer isn’t recommended until age 45.
Many types of cancer that are commonly diagnosed in AYAs have very high survival rates that contribute to the high overall rate. These include thyroid cancer, testicular cancer, melanoma, and Hodgkin lymphoma.
The high 5-year relative survival for these types (all ≥94%) masks lower survival for several other cancer types. For example, 5-year relative survival is lower in AYA cancer patients compared to children for acute lymphocytic leukemia, 60% versus 91%, respectively.
In addition, 5-year survival for breast cancer is lower in AYA women than in screening-aged women, (86% vs 91% in women aged 45-64 years). The lower survival rate reflects the higher proportion of AYA women diagnosed at a later stage and a higher occurrence of triple-negative disease among AYA women.
The 5-year survival rate in AYAs for all cancer types combined is lower in racial/ethnic minorities. One of the biggest disparities is for female breast cancer. About 89% of non-Hispanic White women survive at least 5 years after being diagnosed with breast cancer. That rate drops to 85% for Hispanic women and to 78% for non-Hispanic Black women.
Non-Hispanic Black AYAs also have the highest cancer death rates, even though they have a 25% lower incidence rate than whites. In women, this disparity is largely due to breast cancer. The breast cancer death rates in non-Hispanic Black women in their 30s are nearly double those in non-Hispanic white women (8.5 vs 4.5 deaths per 100,000 people, respectively). The Black-White disparity in breast cancer death rates is largest in AYAs and declines with age.
Brain tumors are the second leading cause of death from cancer in AYAs overall, after breast cancer. Leukemia continues to be the leading cause of death from cancer in those aged 15 to 29. This point is masked when adolescents’ statistics are combined with children—where brain tumors are the leading cause of cancer death.
Nearly 1 out of 3 women are diagnosed with cervical cancer after it has spread outside the cervix. This may reflect some women delaying screening exams or having a more aggressive subtype, particularly in younger AYA women.
Most cervical cancers develop slowly, so cancer can usually be prevented if a woman is screened regularly. Indeed, most women diagnosed with cervical cancer have not been screened recently.
Smoking may also increase susceptibility of developing cervical cancer. It’s one of the few smoking-related cancers that’s among the more common in AYAs.
Although it is highly preventable, cervical cancer is the second leading cause of cancer death among AYA women overall.
AYA cancer survivors have:
Notably, a substantial proportion of AYA patients with cancer, especially women, do not receive adequate information about fertility preservation. In one study of AYA cancer survivors, 18% of males and 38% of females who did not make fertility-preservation arrangements failed to do so because they were not aware of their options.