美国中青年人结直肠癌发病率迅猛增高

Colorectal cancer incidence rising sharply among younger adults

来源：爱思唯尔

旧金山——一项研究显示，美国中青年人中的结直肠癌发病率正在迅猛增高。

研究者分析了监督、流行病学与终点结果(SEER)研究中于1975~2010年之间被诊断为结直肠癌的383,241例患者的数据。M.D. Anderson 肿瘤中心的肿瘤外科研究员Christina E. Bailey博士在年度胃肠肿瘤研讨会上报告了上述结果。

该研究显示，在诊断时年龄≥50岁的患者中，经校正年龄的结直肠癌发病率稳定下降，但在较年轻患者中发病率增高。35年期间，总体队列中经校正年龄的结直肠癌年发病百分率变化为–0.92。在分层分析中，诊断年龄为50~74岁(–0.97)和≥75岁的患者年发病百分率显著降低(–1.15)。但诊断年龄为35~49岁的患者年发病百分率增高(0.41)，尤其是诊断年龄为20~34岁的患者增高更为明显 (1.99)。对于单独的结肠癌（诊断时有远处疾病的结果最强）和直肠/乙状结肠癌，结果相似。

一项预测模型提示，如果这一趋势在2010~2030之间仍持续，则在20~34岁人群结肠癌和直肠/乙状结肠癌的发病率将分别增加90%和124%，在35~49岁的人群中将分别增加28%和46%。在较年老人群中，发病率降低的大部分原因“可归结为建议从50岁开始进行筛查，”Bailey博士在接受采访时评论道。尽管较年轻人群中的发病率增高，其绝对发病率仍显著低于年龄≥50岁的人群。

Bailey博士披露无相关利益冲突。

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By: SUSAN LONDON, Internal Medicine News Digital Network

SAN FRANCISCO – The incidence of colorectal cancer is rising sharply among younger adults in the United States, a study showed.

Researchers analyzed Surveillance, Epidemiology, and End Results (SEER) data for 383,241 patients in whom colorectal cancer was diagnosed between 1975 and 2010.

The results showed that the age-adjusted incidence rate of colorectal cancer fell steadily among patients aged 50 years and older at diagnosis, lead author Dr. Christina E. Bailey, a surgical oncology fellow at the M.D. Anderson Cancer Center in Houston, reported in a poster session at the annual Gastrointestinal Cancers Symposium. But the rate rose among younger patients.

The annual percentage change in the age-adjusted incidence rate of colorectal cancer during the 35-year period was a significant –0.92 in the cohort overall. In stratified analyses, the annual percentage change fell significantly among patients aged 50-74 at diagnosis (–0.97), and aged 75 years and older at diagnosis (–1.15). But it rose among patients aged 35-49 at diagnosis (0.41) and especially among patients aged 20-34 at diagnosis (1.99).

The findings were similar for colon cancer separately (with strongest results seen for disease that was distant at diagnosis) and for rectal/rectosigmoid cancer separately.

A predictive model suggested that if the observed trends persist between 2010 and 2030, the incidences of colon cancer and of rectal/rectosigmoid cancer will rise by 90% and 124%, respectively, among 20- to 34-year-olds, and by 28% and 46%, respectively, among 35- to 49-year-olds.

Much of the decreasing incidence among older adults "can be attributed to the fact that screening is recommended beginning at the age of 50," Dr. Bailey commented in an interview.

"We saw dramatic rises in the predicted incidences of both colon and rectal cancer in our younger cohort that point out that further studies need to be done to determine why this is happening and what can we do now to prevent this trajectory from occurring in the future," she said at the symposium, sponsored by the American Society of Clinical Oncology.

Likely explanations for this sharp uptick, she suggested, include increasing population levels of obesity and physical inactivity, and consumption of a diet high in fat and red meat – factors implicated as risks for colorectal cancer.

Another possibility is that primary care physicians are now more alert for this cancer in young patients with symptoms such as rectal bleeding, which previously may have been attributed to conditions such as hemorrhoids, delaying diagnosis until an older age.

Recommendations still call for routine colorectal cancer screening only in those patients younger than age 50 who have risk factors such as familial adenomatous polyposis and Lynch syndrome, Dr. Bailey noted. And even though the incidence is rising in the younger age groups, it is still considerably lower than it is among people aged 50 years and older.

Dr. Bailey said she had no relevant financial disclosures.