Original article
Clinical endoscopy
Ongoing colorectal cancer risk despite surveillance colonoscopy: the Polyp Prevention Trial Continued Follow-up Study

https://doi.org/10.1016/j.gie.2009.05.010Get rights and content

Background

Despite regular colonoscopy, interval colorectal cancer (CRC) may occur. Long-term studies examining CRC rates in patients with previous colonoscopy are lacking.

Objective

We examined the rate of interval CRC in the Polyp Prevention Trial Continued Follow-up Study (PPT-CFS), an observational study of PPT participants that began after the PPT ended.

Design

Prospective.

Setting

A national U.S. community-based polyp prevention trial.

Main Outcome Measurements

Medical records of patients with CRC were collected, reviewed, and abstracted in a standardized fashion.

Results

Among 2079 PPT participants, 1297 (62.4%) agreed to participate in the PPT-CFS. They were followed for a median of 6.2 years after 4.3 years of median follow-up in the main PPT. Nine cases of CRC were diagnosed over 7626 person-years of observation (PYO), for an incidence rate of 1.2/1000 PYO. The ratio of CRCs observed compared with that expected by Surveillance, Epidemiology, and End Results was 0.64 (95% CI, 0.28-1.06). Including all CRCs (N = 22) since the beginning of the PPT, the observed compared with expected rate by Surveillance, Epidemiology, and End Results was 0.74 (95% CI, 0.47-1.05). Of patients in whom CRC developed in the PPT-CFS, 78% had a history of an advanced adenoma compared with only 43% of patients who remained cancer free (P = .04).

Limitation

A relatively small number of interval cancers were detected.

Conclusions

Despite frequent colonoscopy during the PPT, in the years after the trial, there was a persistent ongoing risk of cancer. Subjects with a history of advanced adenoma are at increased risk of subsequent cancer and should be followed closely with continued surveillance.

Section snippets

Study participants

The PPT enrolled 2079 patients who had a baseline enrollment colonoscopy (T0) with at least 1 adenomatous polyp but no history of CRC. Details of the study population have been reported.11 Subjects were randomized to a dietary intervention to adopt a diet low in fat and high in fiber, fruits, and vegetables instead of their usual diet. A repeat colonoscopy was performed in 1 to 2 years (T1) to detect and remove lesions that may have been missed at the baseline colonoscopy. Subjects underwent a

Results

Of 2079 patients enrolled in the PPT, 1905 completed the study. Of those who completed the PPT, 1297 (68%) agreed to participate in the PPT-CFS and were followed for a median of 6.2 years. PPT-CFS participants compared with PPT subjects who did not participate in the PPT-CFS were more likely to be male (67% vs 59%, P < .001), more educated (78% vs 68% post–high school education, P < .001), and to have a family history of CRC (28% vs 24%, P = .03) (Table 1). During the PPT, PPT-CFS participants

Discussion

CRC developed in 9 participants during the PPT-CFS, for a rate of 1.2 cases/1000 PYO, despite undergoing a mean of more than 3 colonoscopies during the PPT. This interval cancer rate was 64% of that expected by SEER, and when cancers detected in the main PPT and the CFS were combined, the overall rate was 74% of that expected by SEER. The absolute rates were not statistically significantly different from that expected based on SEER data. Our study included a relatively prolonged (>10 years)

Acknowledgment

We acknowledge Westat, Inc, for their work as the coordinating center for the PPT-CFS.

References (30)

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DISCLOSURE: All authors disclosed no financial relationships relevant to this publication.

See CME section; p. 139.

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