Cancer

The number of cancers rises every year because the world is ageing. The age-standardised picture is more mixed. Lung cancer in men, stomach cancer and cervical cancer have fallen for decades, whilst liver, kidney, uterine and skin cancers have risen. Colorectal cancer has seen the most consistent and largest rises since the 1990s. Each generation born after about 1960 has higher rates at a given age than the one before, which is the signature of exposure rather than of detection. Detection is still part of the story, as the rise in thyroid cancer is almost entirely diagnostic and lowered screening ages complicate the recent years.

More cancer is found earlier, by design and by accident. Screening for breast, bowel and cervical cancer is national in most of Europe. Low-dose CT screening for lung cancer in smokers is now a programme in England and the United States. A blood test that claims to detect many cancers at once has now reported from a large randomised trial in England: it did not reduce stage III and IV cancers combined, its main measure, though stage IV diagnoses fell by 14%. The pandemic worked the other way, and registry data now show later-stage diagnosis for some sites in 2020 and 2021, with a measurable mortality cost.

Treatment and prevention have moved survival more than incidence. Immunotherapy has changed the outlook in melanoma and some lung cancers. HPV vaccination has all but eliminated cervical cancer in the first fully vaccinated cohorts. Five-year survival has risen for most sites, although the United Kingdom is still behind comparable European countries.

The mortality data show that age-standardised cancer mortality has fallen by around one to two per cent a year in high-income countries for decades, driven by lung cancer, and that the fall continues. The exception is the one that matters for the under-50 question. Colorectal mortality under 50 has risen in some countries, which detection alone does not produce. The candidate causes of the cohort effect — diet, obesity, antibiotics, the microbiome — remain plausible and unproven.

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