Cases of cancer among UK men and women aged 35-69 years have seen a modest rise over the last quarter of a century, but there has also been a substantial decline in death rates, finds a study published by The BMJ today.
The results show a fall in death rates for all cancers combined and for 17 out of 22 cancer types examined, which the researchers say is likely due to fewer people smoking, screening programmes, and improved treatment, while a rise in some less common cancers may be due to higher levels of overweight and obesity, among other risk factors.
The availability of comprehensive UK cancer registration data since 1993 makes comparison of cancer cases (incidence) and mortality trends over 25 years possible, but no recent studies have investigated these trends over such a long time frame.
To fill this knowledge gap, researchers used UK-wide cancer registration and population data to examine trends in cancer cases and deaths for all cancers combined and 22 common cancers in men and women aged 35-69 years who were newly diagnosed with or died from cancer between 1993 to 2018.
Results show the number of cancer cases rose by 57% for men (from 55,014 cases registered in 1993 to 86,297 in 2018) and by 48% for women (60,187 to 88,970).
When analysed by age, the average annual increase in cases was a modest 0.8% in both sexes, predominantly driven by increases in prostate (male) and breast (female) cancers.
However, four less common cancers showed concerning increases in cases (more than 2% per year) in both sexes: liver, melanoma skin, oral, and kidney.
Overall, the number of cancer deaths fell over the 25 year period, by 20% in men (from 32,878 to 26,322) and 17% in women (28,516 to 23,719), with death rates falling even higher by 37% in men and 33% in women when accounting for the growing and ageing population over the 25 year period.
After accounting for differences in age, deaths for all cancers combined fell by 2% per year in men and by 1.6% per year in women across nearly all the cancers examined.
The largest declines were noted for stomach (5.1%), mesothelioma (4.2% from 2001), and bladder cancers (3.2%) in men and stomach (4.2%), cervical cancers (3.6%) and non-Hodgkin's lymphoma (3.2%) in women.
Only liver, oral, and uterine cancers showed an annual increase in deaths of 1% or more.
The authors note that this decline in deaths across the most common cancers in both sexes is likely a reflection of the successes in cancer prevention, earlier detection and improved diagnostic tests and treatment. In contrast, increased levels of alcohol intake and excess body weight are likely factors in the rise in rates of some less common cancers.
This is an observational study so can't establish cause, and the authors acknowledge that cancers not included in the study could well be showing different trends. Excluding older people, where rates of cancer are higher, and being unable to take account of ethnic group and deprivation may have also had an effect.
Nevertheless, by using high quality cancer registry data and focusing only on the 35-69 age range, they present a clear and reliable comparative picture of UK cancer incidence across 25 years.
The conclusions that can be drawn from this analysis are, overall, positive and reassuring, they say. "This analysis also provides a benchmark for the following decade, which will include the impact of covid-19 on cancer incidence and outcomes."
These findings are grounds for optimism, agrees Dr Freddie Bray at the International Agency for Research on Cancer (IARC) in a linked editorial.
However, some early warning signs should raise alarm bells, including the possibility of excess cancer deaths in future years resulting from delays in diagnosis and treatment during the covid-19 pandemic. The rising death rates from common cancers, including among younger (unscreened) age groups, are also of immediate concern, he adds.
"Effective interventions that increase awareness of modifiable risk factors for cancer—including, but not limited to excess body weight and harmful alcohol consumption—must be urgently prioritised," he concludes.
