Expert comment: Global cancer incidence and mortality in young adults
Following the recent publication in The Lancet Oncology of a report on the global incidence of cancer and associated mortality among young adults, medwireNews spoke to Lorna Fern (Teenage, Young Adult and Germ Cell Clinical Studies Group, National Cancer Research Institute, London, UK) about her views on the research and the key challenges faced by physicians looking after young adults with cancer.
What the study adds
Fern described the article – by Miranda Fidler (International Agency for Research on Cancer, Lyon, France) and colleagues – as “a really important paper” and was “not surprised” at the reported incidence of cancer in young people or the lower mortality in this population versus children and older adults. “That’s something we have known for quite a while,” she commented, “particularly for that 15–24-year-old age group, which here in the UK we would typically class as our teenage and young adult population.”
She added, however, that the remit of the Teenage, Young Adult and Germ Cell Clinical Studies research group at the UK’s National Cancer Research Institute does include patients up to the age of 39 years, which was the upper age limit used in The Lancet Oncology study.
Substantial variations in global young adult cancer burden revealed
The paper “provides us with a benchmark” for the cancer incidence and mortality rates in young people and is “a pivotal piece of work” for stimulating the conversation around cancer in this group of patients, Fern said. By identifying the types of cancers that young adults are getting and dying from and providing the data on tumor distribution by age, the study enables us to think about the services and research infrastructure that we need to put in place to ensure that these young people are supported, she continued.
It could also “allow us to reach some consensus on the upper age limit” to define this group of patients “because it can be quite a controversial topic,” with opinions varying across countries, institutions, and research groups, commented Fern.
The key challenges
Noting that cancer is a multistep process resulting from an accumulation of genetic mutations over a lifetime from mainly lifestyle – and occasionally genetic – factors, Fern said that “for our young people, especially those in their 20s, they haven't really been alive long enough to experience those environmental insults – such as diet, cigarette smoking, or environmental agents – to a sufficient degree to cause cancer, so why young people get cancer is still not clear.”
There are exceptions, of course, such as cervical cancer where the link with human papillomavirus (HPV) infection is clear, she observed, which also makes it “probably the most obvious target” in terms of reducing cancer incidence in young adults, especially in light of the global cervical cancer incidence data around the world. “HPV vaccination is a natural starting point,” remarked Fern, noting, however, the challenges with regard to vaccination in lower income countries that have limited resources.
Screening is likewise “invaluable” when it comes to reducing the incidence of cervical cancer, she said, but education is also key. Alongside vaccination and screening, “there has to be an awareness package where you are educating young girls about the importance of using barrier contraception to protect themselves against HPV and attending their screening appointment,” Fern observed. All of this needs resources, which can be difficult in lower-income populations, “but if you look at the cancer incidence, it's obviously a worthwhile thing to do,” she emphasized.
Continuing to discuss the challenges, Fern pointed out that “screening young people for cancers is really difficult.” Although there is a large population of young people with cancer, they make up too small a proportion of cancer diagnoses overall to allow for a national screening program and we lack the appropriate tools for this task, she said.
For instance, it is not effective to screen women aged younger than 50 years for breast cancer because the breast tissue of younger women is not as amenable to the current mammogram screening technology which uses low dose X-rays, explained Fern. “You can screen young people for BRCA1 and BRCA2 mutations, but the frequency of those mutations is also quite low so you wouldn't want to develop a nationwide screening programme.”
Fern believes that another challenge, and one of the reasons for the limited information on why young people develop cancer, is a lack of availability of sufficient biological material. We know from research conducted in individuals in their early 20s – and the findings could possibly be extrapolated up to the 39-year olds – that young adults are less likely to be recruited into clinical trials than children and older adults, she told medwireNews. And it is within the context of clinical trials that high-quality biological samples can be collected, which can be used to identify novel molecular markers or genetic aberrations, but “we just don’t have the infrastructure to collect and analyze tissue from all young people,” she commented.
Furthermore, coordinating a streamlined approach to tissue banking in routine care is also difficult in the young adult setting as “their place of care is much more dispersed” than for pediatric patients who are treated at specialized centers, observed Fern. She added: “We are really fortunate in the UK that we have specialized age-appropriate care units which treat young people generally up to the age of 24, but we know that only half of young people with cancer access those units.”
“Collecting sufficient tissue to understanding the biology of the disease in young people can be quite difficult when they present with numerous cancer types across disparate care settings”, she noted.
Requirements for the future
We need to acquire a deeper understanding of why young people get cancer, said Fern, specifically the biology of the disease, the molecular and genetic drivers, and potential markers that could be used for early diagnosis, accurate screening tests and targeted therapies for this group.
Fern pointed out that three of the top four malignancies that are a focus of research globally –breast, colorectal, lung, and prostate cancer – are not the most common cancers among young adults, as shown by the Fidler et al study. Noting that awareness campaigns often use the most common symptoms associated with these four neoplasms, she commented that these data highlight that this information may not be relevant for young adults, and perhaps awareness campaigns should also encompass rarer cancers such as those seen in young adults.
Highlighting one of the surprising results of the study by Fidler and colleagues, namely that the highest incidence of cancer in young adults was in Australia and New Zealand, driven mainly by melanoma incidence, Fern said that “there is still work to be done around educating young people, and particularly parents, about sun exposure in childhood.” She finds it surprising that the information about sun awareness and melanoma has not filtered through yet, but notes that the study data are from 2012, “so it would be interesting to see more up-to-date information as it becomes available.”
She also stressed the importance of understanding how adolescents and young adults access primary care services in terms of seeking help for potential cancer symptoms; for patients in their 30s, for example, we don’t know whether there are everyday barriers to visiting a family physician.
Fern thinks that the publication of such research in The Lancet Oncology is “really important” because it shines a light on a group of patients that otherwise remain in the shadows. If you are a physician who treats cervical cancer on a regular basis, then you probably are aware of this patient group, but if you see patients with colorectal or lung cancer, “then you are generally not exposed to younger patients and therefore not really thinking about younger people and cancer,” she remarked.
And this research serves to highlight this often under-served group of patients, concluded Fern.
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