Background & Aims

The contribution of surveillance colonoscopy, as opposed to that of initial colonoscopy examination, to prevention of colorectal cancer (CRC) is uncertain. We estimated the preventive effect of surveillance colonoscopy by applying the recently developed metric of adenoma dwell time avoided needed to prevent 1 CRC case (DTA).

Methods

We followed subjects in the prostate, lung, colorectal and ovarian (PLCO) cancer screening trial who underwent colonoscopies following positive findings from sigmoidoscopies (colonoscopy cohort, n = 15,935) for CRC incidence for 10 years. The number and timing of adenomas removed during surveillance were measured in a subset (n = 3492) of patients and extrapolated to the entire cohort to estimate the total avoided adenoma dwell time. A previously determined DTA value of 612 dwell years was applied to estimate the number of CRC cases prevented by surveillance. Proportional reduction in CRC was computed as C_P/(C_O+C_P), where C_O and C_P are observed and estimated prevented cases, respectively.

Results

In the colonoscopy cohort of the PLCO, 2882 subjects had advanced adenomas (AAs), 572 had 3 or more non-advanced adenomas (NAA₃₊), 4496 had 1–2 non-advanced adenomas (NAA_1-2), and 7985 had no adenoma (NA). The mean number of subsequent colonoscopy examinations over 10 years were 1.80 for subjects with AAs, 1.63 for subjects with NAA₃₊, and 1.46 for subjects with NAA_1–2. Average years of avoided adenoma dwell time per subject were 4.0 for subjects with AAs, 5.5 for subjects with NAA₃₊, and 2.4 for subjects with NAA_1–2. There were 56 cases of CRC in subjects with AAs, 4 cases of CRC in subjects with NAA₃₊, and 33 cases of CRC in subjects with NAA_1–2. Estimated proportional reductions in CRC incidence were 25.0% in subjects with AAs (95% CI, 16%–34%), 34.4% in subjects with NAA_1–2 (95% CI, 25%–40%), and 30.4% overall (in subjects with AAs, NAA₃₊, or NAA_1–2; 95% CI, 25%–40%). Absolute CRC incidence reductions were 7.1 per 10,000 PY in subjects with AAs and 4.1 per 10,000 PY in subjects with NAA_1-2.

Conclusions

Using the recently developed metric of DTA, we estimated that surveillance colonoscopy in the PLCO colonoscopy cohort during 10 years of follow up prevented 30% of CRC cases. Because the methodology for estimation is indirect, the true effect is uncertain.

中文翻译：

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结肠镜监测对大肠癌预防的贡献。

背景与目标

与初始结肠镜检查相反，监测结肠镜检查对预防结直肠癌 (CRC) 的贡献尚不确定。我们通过应用最近开发的预防 1 例 CRC 病例 (DTA) 所需避免的腺瘤停留时间指标来估计监测结肠镜检查的预防效果。

方法

我们对前列腺癌、肺癌、结肠直肠癌和卵巢癌 (PLCO) 癌症筛查试验中的受试者进行了 10 年的结肠镜检查，这些受试者在乙状结肠镜检查（结肠镜检查队列，n = 15,935）的阳性结果后接受了结肠镜检查。在监测期间移除的腺瘤的数量和时间在患者的子集 (n = 3492) 中进行测量，并外推到整个队列以估计总避免的腺瘤停留时间。应用先前确定的 612 居住年的 DTA 值来估计通过监视预防的 CRC 病例数。CRC 的成比例减少计算为 C _P /(C _O +C _P )，其中 C _O和 C _P分别是观察和估计的预防病例。

结果

在 PLCO 的结肠镜检查队列中，2882 名受试者患有晚期腺瘤 (AA)，572 名受试者患有 3 个或更多非晚期腺瘤 (NAA ₃₊ )，4496名受试者患有 1-2 个非晚期腺瘤 (NAA _1-2 )，以及 7985没有腺瘤（NA）。10 年内随后结肠镜检查的平均次数对于 AA 受试者为 1.80，对于 NAA ₃₊受试者为 1.63，对于 NAA _1-2受试者为 1.46 。每个受试者避免腺瘤停留时间的平均年数对于 AA 受试者为 4.0，对于 NAA ₃₊受试者为 5.5，对于 NAA _1-2受试者为 2.4 。AA患者有56例CRC，NAA ₃₊患者有4例CRC，NAA患者有33例CRC_1-2。在患有 AA 的受试者中，CRC 发病率的估计比例降低为 25.0%（95% CI，16%–34%），在患有 NAA _{1–2 的}受试者中为 34.4% （95% CI，25%–40%），总体为 30.4% （在患有 AA、NAA ₃₊或 NAA _{1–2 的}受试者中；95% CI，25%–40%）。在患有 AA 的受试者中，CRC 的绝对发病率降低为每 10,000 PY 7.1，在患有 NAA 的受试者中为每 10,000 PY 4.1 _1-2。

结论

使用最近开发的 DTA 指标，我们估计 PLCO 结肠镜检查队列中的监测结肠镜检查在 10 年的随访期间可预防 30% 的 CRC 病例。由于估计方法是间接的，真实的效果是不确定的。