Increasing incidence of early-onset kidney cancer in young adults aged <50 years in England: an analysis of the national cancer registration data by age and gender, 1985-2020

<p dir="ltr"><b>Background</b> <p dir="ltr">The incidence of kidney cancer, which is 34% attributable to obesity and smoking, has been steadily increasing over the past few decades in many countries in Europe, North America and Oceania. In recent years, there have been several reports of increasing incidence of early-onset cancer in young adults aged <50 years. We conducted a retrospective population-based cohort study to examine whether there have been changes in the incidence of kidney cancer in England during the past four decades. <p dir="ltr"><br> <p dir="ltr"><b>Methods</b> <p dir="ltr">Individual-level, national (population-based) cancer registration data for patients diagnosed with kidney cancer (ICD-10 code, C64) in England from 1985-2020 were obtained from the Office for National Statistics/Public Health England. Average annual incidence rates (AAIR) were calculated by two age categories (<50, 50+ years) and gender during the six five-year time periods (1985-89 to 2010-14) and the recent six-year period (2015-20). The percentage change in the incidence rates in each age group and gender was calculated as the change in the AAIR from the first (1985-89) to the last time period (2015-20). The Average Annual Percentage Change (AAPC, year-on-year increase in incidence rates during 1985-2000) was estimated using the slope of the linear trend line fitted to the incidence rates by year of diagnosis. <p dir="ltr"><br> <p dir="ltr"><b>Results</b> <p dir="ltr">During the 36-year study period (1985-2020), a total of 206,816 cases (62.4% males, 37.6% females) of kidney cancer were registered in England. In young adults aged <50 years, the AAIRs (per 100,000 population) increased by 157% in males and 133% in females (from 1.4 in 1985-89 to 3.6 in 2015-20 in males and from 0.9 in 1985-89 to 2.1 in 2015-20 in females). In older adults aged 50+ years, the AAIRs increased by 127% in males and 144% in females (from 24.5 in 1985-89 to 55.5 in 2015-20 in males and from 11.9 in 1985-89 to 29.0 in 2015-20 in females). The AAPC during the 36-year period was 5.0% in people aged <50 years compared to 4.7% in those aged 50+ years. <p dir="ltr"><br> <p dir="ltr"><b>Conclusion</b> <p dir="ltr">There has been a steady and substantial increase in the incidence of kidney cancer in England over the past four decades. This was partly driven by the largest and unexpected increase in the incidence of early-onset kidney cancer in young adults aged <50 years, which was steepest in males. Some of this increase is in analogy with the increasing prevalence of obesity; nevertheless, other causes driving this increase in early-onset kidney cancer in young adults remain elusive and need further investigation.