Colorectal (CRC) cancer deaths increased significantly among white people younger than 55 during the past 2 decades, an epidemiologic reversal coinciding with the obesity epidemic, American Cancer Society (ACS) researchers reported.
Deaths from colorectal cancer began to increase 2 decades ago in whites ages <40, and by 2005 the trend expanded to include whites ages <55. The data add to results of a recent ACS study showing an increased incidence of CRC in people ages <55, driven by an increase in whites, according to Rebecca Siegel, MPH, of the ACS Surveillance and Health Services Research Program in Atlanta, and colleagues.
Collectively, the data run counter to the broad epidemiologic picture showing improved 5-year survival in CRC across the age range of 15 to 64, they noted in a research letter in JAMA.
"Although 5-year survival in persons ages 15 to 64 years has improved, mortality is a function of incidence and survival and can increase if CRC occurrence is of sufficient magnitude to outweigh improvements in survival," according to Siegel's group. "Increased mortality is particularly unexpected among those ages 50 to 54 years, for whom screening has been recommended since the 1970s."
In contrast to the incidence and mortality data for whites, CRC incidence and mortality remained stable in blacks. The racial disparity is perplexing, given that trends for major CRC risk factors, including obesity, are similar between the races, the authors said.
Although obesity is the prime suspect in the rising incidence and mortality among whites, a number of other factors could be contributing to the findings, said Alok Khorana, MD, of the Cleveland Clinic.
"The short answer is: We have no idea," Khorana told MedPage Today. "The long answer is that it's probably related to environmental risk factors. A lot of people have pointed to the rising level of obesity in the United States. That's certainly a known risk factor for colorectal cancer, as is [consumption of] red meat and bacon and so on."
The racial disparity seen in the studies of CRC incidence and mortality added to "the sort of mystery surrounding this. Obesity prevalence is similar among blacks and whites, so when rates improve for younger black patients but not younger white patients, it is a little bit of a mystery."
Whether the incidence and mortality data make a case for revisiting screening recommendations for CRC remains to be seen, Khorana said. Although the adverse trends in younger white people are worrisome, rates in older individuals have decreased, consistent with a favorable impact of screening on early detection and treatment.
Siegel's group noted that CRC mortality continues to decline in the overall population. However, mortality trends in a broad population can mask differing patterns among specific age groups. To address the issue, the ACS investigators analyzed CRC mortality by race from 1970 through 2014 among people ages 20 to 54. Data for the analysis came from the NCI Surveillance, Epidemiology, and End Results cancer registry program.
Overall, 242,637 people died of CRC during the 44-year study period. Men accounted for 54% of the deaths, and whites accounted for 80%. The authors calculated changes in CRC mortality on the basis of CRC deaths per 100,000 population, and they performed trend analyses for a variety of time periods, ranging from 3 to 20 years.
The authors analyzed CRC mortality by decade of age from 20 through 49, as well as 50 to 54. The first evidence of increased mortality occurred during 1994 to 2014 in the 30-to-39 age group (0.7%, 95% CI 0.7-1.4%). For people ages 20 to 29 and ages 40 to 49, CRC mortality increased by 0.1% and 1.1%, respectively, during the same 20-year period, but the increases were associated with overlapping statistical confidence intervals.
An analysis of CRC mortality during 2004 to 2014 produced a 1.4% increase among individuals ages 40 to 49 (95% CI 0.8-1.9%), and the 50-to-54 age group had a 0.8% increase in CRC mortality during 2005 to 2014 (95% CI 0.2-1.3%).
Stratification of the data by race showed that CRC mortality increased by 0.5% (95% CI 0-1.0%) from 1988 to 2014 among whites ages 20 to 29, and increased by 1.6% (1.2-2.1%) from 1995 to 2014 among whites ages 30 to 39. CRC mortality increased by 1.9% (95% CI 1.2-2.5%) from 2005 to 2014 among whites ages 40 to 49 and by 0.9% (0.1-1.6%) during 2005 to 2014 among whites ages 50 to 54.
Stratified analyses for blacks, though more limited because of a smaller population, consistently showed reductions in CRC mortality across all the age groups, ranging from -0.5% (95% CI -0.6 to -0.4%) for ages 40 to 49 during 1970 to 2014 to -2.1% (95% -2.5% to -1.6%) for ages 20 to 29 during 1970 to 2014. CRC mortality declined by 1.1% among blacks 50 to 54 during 1993-2014.
The study was funded by ACS.
Siegel and co-authors disclosed no relevant relationships with industry.
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