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According to data provided by Cancer Research UK, the lowest rate of cancer incidence by age occurs between 5 and 15 years. Infants have a higher rate, and the odds of an adult developing cancer increase over time, especially during old age; until the odds plateau around age 85.

I understand that an accumulation of DNA damage over time increases likelihood of cancer with age. But what explains the almost flatline rate of cancer amongst those aged 5-15? Surely it makes more sense for the rate of cancer to increase uniformly every year from infancy?

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    $\begingroup$ "Surely it makes more sense..." doesn't correspond to reality, and isn't an argument. It made more sense for thousands of years that the earth was flat and that spontaneous generation of life existed (after all, people saw it with their own eyes.) Please take into account not only damage of DNA as a cause of cancer (in that case, there would be no childhood cancers) but genetic predispositions and other causes. "Childhood cancers" is easy to google. $\endgroup$
    – anongoodnurse
    Aug 10, 2017 at 12:38
  • $\begingroup$ @anongoodnurse I know I'm just supposing based on a general understanding, which is limited and incorrect; which is why I ask. :) $\endgroup$
    – user24803
    Aug 10, 2017 at 12:40
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    $\begingroup$ It's a good question (+1). The site asks that you make an attempt at answering your own question before asking. See the help section, or look at the close reasons. Googling childhood cancers and editing your question will likely get you a better answer. Thanks. $\endgroup$
    – anongoodnurse
    Aug 10, 2017 at 14:15

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I think one of the conclusions you can draw from your chart is that older adults are more frequently diagnosed with cancer as a disease. Cancer is an accumulation of genetic abnormalities due to genetic instability, and so for children this occurs during embryogenesis (there are caveats), and we can see that these cancers seem to occur in cells that are quite active during development. We can actually see that adult cancers seem to occur in established tissues at an older age (probably due to inflammation, check out SITC's new book on immunotherapy and cancer).

So you can do this with cancerresearchuk's website: the stat for childhood cancers is that brain tumors and leukemia occur significantly more frequently, which actually differs in overall distribution from the world significantly (ref). enter image description here

Figure 1. Cancer incidence in children 0-15 by type.

If you stratify by age by those particular cancers, it's much less of a flat line in the 0-15 age bracket. Explaining why is probably a different question all together. The distribution of types of cancer is different for children than for older adults. Thus, the comparison is made difficult because this isn't a straightforward comparison. The best answer is that certain cancers are actually more frequent in children than in older adults and vice versa.

You can start here. Some of the things you will find interesting:

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Figure 2. Hodgkin Lymphoma, incidence by age bracket. Interesting to note that non-Hodgkin lymphoma does not occur with any appreciable frequency in children or young adults!

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Figure 3. Leukemia, incidence by age bracket.

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Figure 4. ALL, a type of leukemia, incidence by age bracket. Based on the data in the OP, you would expect incidence to be highest for 60-74yr olds, but this is not the case.

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Figure 5. Brain/CNS tumors, incidence by age bracket.

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Figure 6. Bone Sarcoma, incidence by age bracket.

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There are 2 main causes of cancer: "born defective" (heritable or genetic problems producing a large predisposition to cancer) and "accumulated damage" (random mutations accumulated over life).

Due to how the UK health system rations treatment (and the recent stories about Charlie Gard being prevented from traveling to the U.S. or Vatican for treatment), it's likely that the government there often "deprioritizes" (complete guess, no idea if they actually do that) infants with severe heritable/genetic problems causing near-immediate cancer. Obviously this means that those cases never live to the 05-09 age bracket.

Cancer deaths peak at 65 rather than 90 or 100 on similar statistical grounds, although late-in-life cancers are almost always due to accumulated mutations rather than being born defective. Cancer deaths drop off after age 79 because of the relatively large die-offs in the previous few age brackets, in addition to deaths from old age and related conditions.

If there was infinite funding for health treatment and enough hospitals to match, the graph might instead match your expectations as the public would do everything to maximize survival. This means that some of the 00-04 bracket would survive to later age brackets, with the largest cause of death in those cancers being failed treatment.

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More to the point, I think, is the age at which the genetic insult that leads to cancer occurs. It implies that there are two causes, the steady increase of genetic damage over time (standard environmental insults) and the introduction of a specific agent of cancer induction which emerged only recently. Here's an explanation of one of many theories: https://vimeo.com/497792887 The specific mechanisms of action would be homologous recombination and insertional mutagenesis, which correlate with changes in the formulations of the agents. This would explain gender differences in the pediatric population (XX vs XY).

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