大腸直腸癌風險受到性別、年齡與出生年影響作者：Roxanne Nelson
出處：WebMD醫學新聞
June 2, 2010 — 根據德國全國大腸鏡篩檢計劃的資料分析，男性有較高的大腸直腸癌與末期疾病發生率，大腸直腸癌和末期腫瘤盛行率隨著年齡適度增加，但是在各年齡層，男性都比女性高。
在6月內科醫學誌(Annals of Internal Medicine)的報告中，研究者也根據男性和女性的出生世代探討末期大腸直腸腫瘤的年齡特定盛行率，他們觀察到一個強烈世代效果，顯示較晚出生的世代其盛行率比那些較早出生的世代增加。
作者們指出，這個強烈的世代效果是令人不安的，因為它可能代表未來幾年的大腸直腸腫瘤會持續增加。
【男性盛行率較高】
之前的研究顯示，大腸直腸癌風險隨著年齡增加，男性風險高於女性，不過，之前的研究並未將年齡的影響從出生世代(出生年)的影響中區隔。在目前的研究中，海德堡德國癌症研究中心的Hermann Brenner醫師等人，試圖估計年齡和出生世代對於末期大腸直腸癌的影響，研究對象是參與德國大腸鏡篩檢計畫的患者。
另一個研究目標是，校正男性的風險-惡化期間對出生世代的影響，和女性的資料比較。
研究對象包括了在2005至2007年間、參與德國大腸癌篩檢計畫、年齡55-75歲的2,185,153名患者，多數研究對象是女性，特別是年齡較輕的組別。
共有17,196名研究對象(0.8%)有大腸直腸癌，152,429人(7.0%)有任何類型的末期癌症，整體而言，大腸直腸癌與末期腫瘤盛行率顯示，在各年齡層中，比率隨著年齡適度增加，且在各年齡層，男性都比女性高。
在每個年齡組中，男性的盛行率最多是女性的2倍。55、60和65歲男性的大腸直腸癌盛行率，則分別和年齡較大的63、69和74歲婦女相當。作者們觀察發現，女性要到70歲才會達到55歲男性的任何末期腫瘤盛行率，此外，女性到75歲時，仍未達到60和65歲男性的盛行率。
【根據年齡和性別的大腸鏡檢查發現】
| 年齡、歲 | 研究對象人數 | 大腸直腸癌，人數(%) | 任何末期癌症，人數(%) |
| 男性 | | | |
| 55–59 | 236,028 | 1,422 (0.6) | 16,810 (7.1) |
| 60–64 | 272,832 | 2,494 (0.9) | 24,255 (8.9) |
| 65–69 | 281,400 | 3,388 (1.2) | 28,491 (10.1) |
| 70–75 | 170,073 | 3,056 (1.8) | 19,646 (11.6) |
| 所有男性 | 960,333 | 10,360 (1.1) | 89,202 (9.3) |
| 女性 | | | |
| 55–59 | 351,716 | 1,090 (0.3) | 13,351 (3.8) |
| 60–64 | 354,559 | 1,633 (0.5) | 17,352 (4.9) |
| 65–69 | 330,965 | 2,183 (0.7) | 19,224 (5.8) |
| 70–75 | 187,580 | 1,930 (1.0) | 13,300 (7.1) |
| 所有女性 | 1,224,820 | 6,836 (0.6) | 63,227 (5.2) |
【控制生育世代】
在橫斷面分析中，研究者發現，每隔10歲，大腸直腸癌盛行率即略微增加2.1倍，不過，控制出生世代或年份之後，每隔10歲，年齡斜率增加到將近6倍。
作者們指出，對於任何末期腫瘤，年齡斜率較不明顯。至於大腸直腸癌，在橫斷面分析中控制出生世代之後，年齡斜率比較強烈(相對盛行率為2.3 vs 1.4)，出生年每隔10年，末期疾病的盛行率增加1.6倍。
再次強調，在橫斷面分析中，男性相較於女性的風險-惡化期間，據估計，大腸直腸癌者需要8.4年，任何末期腫瘤為16.1年。控制出生世代之後，這些人較不明確，但是依舊存在(分別是3.4 年和6.9年)。
他們也比較了較晚和較早出生世代間的風險-惡化期間，每隔10年出生年，大腸直腸癌是5.9年、任何末期癌症是5.7年。
【原因依舊不清楚】
雖然作者們無法確認強烈世代影響的原因，他們推測，這可能是許多因素的結果，包括風險因素分布有不令人接受的改變，例如肥胖、糖尿病與女性抽菸。
他們也指出，理論上，世代影響可能反應出篩檢族群隨著時間的組成變化，也就是說，後來幾年出生、有腫瘤的患者，較多人使用篩檢式大腸鏡檢查，或者，促使由內視鏡醫師偵測末期大腸直腸腫瘤。
作者們結論表示，長期的風險惡化期間持續，需要謹慎的後續評估、探討其篩檢政策的可能適當性。至於較晚出生世代的大腸直腸腫瘤盛行率增加，須努力辨識、使其穩定，理想的話，逆轉不為人接受的風險因素趨勢應是預防策略的首要之務。
本研究並無外界資金，研究者皆宣告沒有相關財務關係。
Colorectal Cancer Risk Influenced by Sex, Age, and Birth Year
By Roxanne Nelson
Medscape Medical News
June 2, 2010 — Men have a higher prevalence of colorectal cancer and advanced disease, according to an analysis of data from a national German colonoscopy screening program. The prevalence of colorectal cancer and advanced neoplasm moderately increased with age, but was higher in men than in women in all age groups.
The researchers, reporting in the June issue of the Annals of Internal Medicine, also looked at the age-specific prevalence of advanced colorectal neoplasms by birth cohort among men and women. They observed a strong cohort effect that showed increases in prevalence in later birth cohorts, as opposed to earlier, birth cohorts.
This strong cohort effect, note the authors, "is disquieting because it might indicate an increasing burden of colorectal neoplasm in the years to come."
Prevalence Higher in Men
Previous studies have shown that the risk for colorectal cancer increases with age, and that the risk is higher in men than in women. However, previous research has not separated the influence of age from the influence of birth cohort (year of birth). In the current study, Hermann Brenner, MD, MPH, from the German Cancer Research in Heidelberg, and colleagues sought to estimate the effects of age and birth cohort in advanced colorectal cancer among people who participated in the German colonoscopy screening program.
Another goal of the study was to adjust risk-advancement periods for men, compared with women, for birth cohort effects.
The study population consisted of 2,185,153 people 55 to 75 years of age who participated in a colon cancer screening program in Germany from 2005 to 2007. The majority of participants were women, particularly in the younger age groups.
A total of 17,196 participants (0.8%) had colorectal cancer, and 152,429 (7.0%) had any type of advanced cancer. Overall, the prevalence of colorectal cancer and advanced neoplasm showed a moderate increase with age and in all age groups was higher in men than in women.
In each age group, prevalence was up to 2 times higher in men than in women. The prevalence of colorectal cancer in men 55, 60, and 65 years of age was reached in much older women — 63, 69, and 74 years, respectively. The authors observed that the prevalence of any advanced neoplasm in men 55 years of age was reached in women at 70 years. Likewise, prevalence in men at 60 and 65 years was not attained by women who were 75 years of age.
Colonoscopy Findings by Age and Sex
| Age, y | Number of Participants | Colorectal Cancer, n (%) | Any Advanced Cancer, n (%) |
| Men | ? | ? | ? |
| 55–59 | 236,028 | 1,422 (0.6) | 16,810 (7.1) |
| 60–64 | 272,832 | 2,494 (0.9) | 24,255 (8.9) |
| 65–69 | 281,400 | 3,388 (1.2) | 28,491 (10.1) |
| 70–75 | 170,073 | 3,056 (1.8) | 19,646 (11.6) |
| All men | 960,333 | 10,360 (1.1) | 89,202 (9.3) |
| Women | ? | ? | ? |
| 55–59 | 351,716 | 1,090 (0.3) | 13,351 (3.8) |
| 60–64 | 354,559 | 1,633 (0.5) | 17,352 (4.9) |
| 65–69 | 330,965 | 2,183 (0.7) | 19,224 (5.8) |
| 70–75 | 187,580 | 1,930 (1.0) | 13,300 (7.1) |
| All women | 1,224,820 | 6,836 (0.6) | 63,227 (5.2) |
Controlling for Birth Cohort
In a cross-sectional analysis, the researchers found that the prevalence of colorectal cancer increased modestly — a 2.1-fold increase per decade of age. However, after controlling for birth cohort or year, the age gradient increased to almost 6-fold per decade of age.
For any advanced neoplasm, the authors note that the age gradient was less pronounced. As for colorectal cancer, the age gradient was much stronger after controlling for birth cohort than in the cross-sectional analysis (relative prevalence, 2.3 vs 1.4). The prevalence for advanced disease increased 1.6-fold per decade of birth year.
Again in the cross-sectional analysis, the risk-advancement periods for men vs women were estimated to be 8.4 years for colorectal cancer and 16.1 years for any advanced tumor. After controlling for birth cohort, these numbers were less pronounced but still substantial (3.4 and 6.9 years, respectively).
They also compared risk-advancement periods for later and earlier birth cohorts, which were 5.9 years for colorectal cancer and 5.7 years for any advanced cancer per decade of birth.
Reasons Remain Unclear
Although the authors were unable to determine the reason for the strong cohort effect, they speculated that it could be the result of a number of factors, including unfavorable shifts in risk-factor distributions such as obesity, diabetes, and smoking among women.
They also note that, in theory, the cohort effect could "reflect the changes in the composition of the screening population over time — that is, greater use of screening colonoscopy by those with prevalent neoplasms in later years, or enhanced detection of advanced colorectal neoplasms by endoscopists in later years."
The authors conclude that "risk-advancement periods of substantial length persist, and their potential relevance for screening policies requires careful further evaluation." As far as the increasing prevalence of colorectal neoplasms in later birth cohorts, efforts are needed to identify, stabilize, and ideally reverse unfavorable risk-factor trends should be a priority for prevention.
This study did not have outside funding sources. The researchers have disclosed no relevant financial relationships.
Ann Intern Med. 2010;152:697-703.
