Five-year risk of colorectal neoplasia after negative colonoscopy

Clear colonoscopy as a surveillance tool in the prediction and reduction of advanced neoplasms: a randomized controlled trial

BACKGROUND

Missed and incompletely resected lesions remain the main cause of the recurrence of advanced neoplasms (ANs) in post-polypectomy patients. This study aims to determine whether the recurrence of ANs can be predicted and reduced by the newly developed clear colonoscopy procedure.

METHODS

Between 2006 and 2010, a total of 1350 participants with colorectal neoplasm were equally randomized to clear colonoscopy surveillance (CCS) and routine colonoscopy surveillance (RCS) in our center. Clear colonoscopy was achieved through repeat colonoscopy. On surveillance colonoscopy at 3 (for high-risk patients) and 5 (for low-risk patients) years, the recurrence of ANs and the relationship between the frequency of repeat examinations required for a clear colonoscopy and the recurrence of ANs were analyzed.

RESULTS

Surveillance colonoscopy at 3 and 5 years showed that the incidence of ANs in patients belonging to the CCS group was 1.7%, which was lower than 4.7% in patients belonging to the RCS group (P = 0.012) for both high- and low-risk patients. Out of the 1126 patients who achieved clear colonoscopy on first repeat examination, only 5 ( 0.4%) were found to have ANs on surveillance examination, whereas 12 out of the 217 (5.4%) patients on second repeat examination and 5 out of the 29 (17.2%) patients on third repeat examination were found to have ANs (P < 0.001).

CONCLUSION

Surveillance based on clear colonoscopy decreased the incidence of ANs in post-polypectomy patients. The number of repeat examinations required for a clear colonoscopy is an important factor in the prediction of the recurrence of ANs.

The efficacy of a leukotriene receptor antagonist in the treatment of human rectal aberrant crypt foci: a nonrandomized, open-label, controlled trial

BACKGROUND

Leukotriene receptor antagonists (LTRAs) are broadly used for the management of allergic asthma and have recently been indicated to inhibit carcinogenesis and cancer cell growth. In colorectal cancer (CRC) chemoprevention studies, the occurrence of adenoma or CRC itself is generally set as the trial endpoint. Although the occurrence rate of CRC is the most confident endpoint, it is inappropriate for chemoprevention studies because CRC incidence rate is low in the general population and needed for long-term monitoring. Aberrant crypt foci (ACF), defined as lesions containing crypts that are larger in diameter and darker in methylene blue staining than normal crypts, are regarded to be a fine surrogate biomarker of CRC. Therefore, this prospective study was designed to explore the chemopreventive effect of LTRA on colonic ACF formation and the safety of the medicine in patients scheduled for a poly resection as a pilot trial leading the CRC chemoprevention trial.

METHODS

This study is a nonrandomized, open-label, controlled trial in patients with colorectal ACF and polyps scheduled for a polypectomy. Participants meet the inclusion criteria will be recruited, and the number of ACF in the rectum will be counted at the baseline colonoscopic examination. Next, the participants will be assigned to the LTRA or no treatment group. Participants in the LTRA group will continue 10 mg of oral montelukast for 8 weeks, and those in the no treatment group will be observed without the administration of any additional drugs. At the end of the 8-week LTRA intervention period, a polypectomy will be conducted to evaluate the changes in the number of ACF, and cell proliferation in the normal colorectal epithelium will be analyzed.

DISCUSSION

This will be the first study to investigate the effect of LTRAs on colorectal ACF formation in humans.

TRIAL REGISTRATION

This trial has been registered in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry as UMIN000029926 . Registered 10 November 2017.

Chemoprevention of colorectal cancer: Past, present, and future

Chemoprevention began to be considered as a potential strategy for lowering the incidence of cancer and cancer-related deaths in the 1970s. For clinical chemoprevention trials against cancer, including colorectal cancer (CRC), well-established biomarkers are necessary for use as reliable endpoints. Difficulty in establishing validated biomarkers has delayed the start of CRC chemoprevention development. Chemoprevention trials for CRC have only recently been initiated thanks to the identification of reliable biomarkers, such as colorectal adenomas and aberrant crypt foci. Some promising agents have been developed for the prevention of CRC. The chemopreventive effect of selective cyclooxygenase 2 inhibitors has been shown, although these inhibitors are associated with cardiovascular toxicity as a crucial adverse effect. Aspirin, which is a unique agent among non-steroidal anti-inflammatory drugs (NSAIDs) showing minimal gastrointestinal toxicity and no cardiovascular risk, has prevented adenoma recurrence in some randomized controlled trials. More recently, metformin, which is a first-line oral medicine for type 2 diabetes, has been shown to be safe and to prevent adenoma recurrence. A recommendation of the United States Preventive Services Task Force published in 2016 provides a Grade B recommendation for the use of aspirin for chronic prophylaxis against diseases, including CRC, in certain select populations. However, the roles of other agents have yet to be determined, and investigations to identify novel "post-aspirin" agents are also needed. The combined use of multiple drugs, such as aspirin and metformin, is another option that may lead not only to stronger CRC prevention, but also to improvement of other obesity-related diseases.

Inhibitory effect of metformin therapy on the incidence of colorectal advanced adenomas in patients with diabetes

BACKGROUND/AIMS

Metformin use has been associated with decreased colorectal cancer risk and mortality among diabetic patients. Recent research suggests that metformin use may decrease the incidence of colorectal adenomas in diabetic patients with previous colorectal cancer. This study aimed to assess the clinical effect of metformin use on the development of colorectal adenomas in diabetic patients without previous colorectal cancer.

METHODS

Among 604 consecutive diabetic patients who underwent colonoscopic surveillance after initial colonoscopy between January 2002 and June 2012, 240 patients without previous colorectal cancer were enrolled in this study and were divided in two groups: 151 patients receiving metformin and 89 patients not receiving metformin. Patient demographics and clinical characteristics as well as the colorectal adenoma incidence rate were retrospectively analyzed.

RESULTS

The incidence rate of total colorectal adenomas was not different according to metformin use (P=0.349). However, the advanced adenoma incidence rate was significantly lower in the metformin group compared with the non-metformin group (relative risk [RR], 0.09; P=0.011). Metformin use was independently associated with a decreased incidence of advanced colorectal adenomas after adjustment for clinically relevant factors (RR, 0.072; P=0.016). In addition, the cumulative development rate of advanced adenomas during follow-up was significantly lower in the metformin group compared with the non-metformin group (P=0.007).

CONCLUSIONS

Metformin use in diabetic patients without previous colorectal cancer is associated with a lower risk of advanced colorectal adenomas.

Eicosapentaenoic acid (EPA) efficacy for colorectal aberrant crypt foci (ACF): a double-blind randomized controlled trial

BACKGROUND

Colorectal cancer (CRC) is one of the most commonly occurring neoplasms and a leading cause of cancer death worldwide, and new preventive strategies are needed to lower the burden of this disease. Eicosapentaenoic acid (EPA), the omega-3 polyunsaturated fatty acid that is widely used in the treatment of hyperlipidemia and prevention of cardiovascular disease, has recently been suggested to have a suppressive effect on tumorigenesis and cancer cell growth. In CRC chemoprevention trials, in general, the incidence of polyps or of the cancer itself is set as the study endpoint. Although the incidence rate of CRC would be the most reliable endpoint, use of this endpoint would be unsuitable for chemoprevention trials, because of the relatively low occurrence rate of CRC in the general population and the long-term observation period that it would necessitate. Moreover, there is an ethical problem in conducting long-term trials to determine whether a test drug might be effective or harmful. Aberrant crypt foci (ACF), defined as lesions containing crypts that are larger in diameter and stain more darkly with methylene blue than normal crypts, are considered as a reliable surrogate biomarker of CRC. Thus, we devised a prospective randomized controlled trial as a preliminary study prior to a CRC chemoprevention trial to evaluate the chemopreventive effect of EPA against colorectal ACF formation and the safety of this drug, in patients scheduled for polypectomy.

METHODS

This study is a multicenter, double-blind, placebo-controlled, randomized controlled trial to be conducted in patients with both colorectal ACF and colorectal polyps scheduled for polypectomy. Eligible patients shall be recruited for the study and the number of ACF in the rectum counted at the baseline colonoscopy. Then, the participants shall be allocated randomly to either one of two groups, the EPA group and the placebo group. Patients in the EPA group shall receive oral 900-mg EPA capsules thrice daily (total daily dose, 2.7 g per day), and those in the placebo group shall receive oral placebo capsules thrice daily. After one month's treatment with EPA/placebo, colonoscopic examination and polypectomy will be performed to evaluate the formation of ACF, and the cell-proliferative activity and cell-apoptotic activity in normal colorectal mucosa and colorectal polyps.

DISCUSSION

This is the first study proposed to explore the effect of EPA against colorectal ACF formation in humans.This trial has been registered in the University hospital Medical Information Network (UMIN) Clinical Trials Registry as UMIN000008172.

Metformin efficacy and safety for colorectal polyps: a double-blind randomized controlled trial

BACKGROUND

Colorectal cancer is one of the major neoplasms and a leading cause of cancer death worldwide, and new preventive strategies are needed to lower the burden of this disease. Metformin, a biguanide, which is widely used for treating diabetes mellitus, has recently been suggestive to have a suppressive effect on tumorigenesis and cancer cell growth. In a previous study conducted in non-diabetic subjects, we showed that oral short-term low-dose metformin suppressed the development of colorectal aberrant crypt foci (ACF). ACF have been considered as a useful surrogate biomarker of CRC, although the biological significance of these lesions remains controversial. We devised a prospective randomized controlled trial to evaluate the chemopreventive effect of metformin against metachronous colorectal polyps and the safety of this drug in non-diabetic post-polypectomy patients.

METHODS/DESIGN

This study is a multi-center, double-blind, placebo-controlled, randomized controlled trial to be conducted in non-diabetic patients with a recent history of undergoing colorectal polypectomy. All adult patients visiting the Yokohama City University hospital or affiliated hospitals for polypectomy shall be recruited for the study. Eligible patients will then be allocated randomly into either one of two groups: the metformin group and the placebo group. Patients in the metformin group shall receive oral metformin at 250 mg per day, and those in the placebo group shall receive an oral placebo tablet. At the end of 1 year of administration of metformin/placebo, colonoscopy will be performed to evaluate the polyp formation.

DISCUSSION

This is the first study proposed to explore the effect of metformin against colorectal polyp formation. Metformin activates AMPK, which inhibits the mammalian target of rapamycin (mTOR) pathway. The mTOR pathway plays an important role in the cellular protein translational machinery and cell proliferation. Patients with type 2 diabetes taking under treatment with metformin have been reported to be at a lower risk of cancer development than those not taking under treatment with metformin. We showed in a previous study that metformin suppressed the formation of human colorectal ACF. We therefore decided to conduct a study to determine whether metformin might suppress the formation of human colorectal polyps.

TRIAL REGISTRATION

This trial has been registered in the University hospital Medical Information Network (UMIN) Clinical Trials Registry as UMIN000006254.

Low risk of colorectal cancer and advanced adenomas more than 10 years after negative colonoscopy

BACKGROUND & AIMS

Screening colonoscopy is an effective method to reduce the incidence of and mortality from colorectal cancer (CRC). There is little empirical evidence available about the optimal interval for screening, making this a subject of debate. We associated the prevalence of advanced colorectal neoplasms with time since negative colonoscopies.

METHODS

In a study of participants in the German colonoscopy screening program, we determined the prevalence of colorectal neoplasias detected at screening colonoscopy among subjects who had undergone a previous colonoscopy without detection of polyps (negative colonoscopy). Data were compared with that from subjects who had not received colonoscopies.

RESULTS

No CRCs were detected in participants who had a previous negative colonoscopy an average of 11.9 years previously (n = 553), compared with the 8.4 CRC cases expected based on age- and gender-specific prevalences among participants who had not received a colonoscopy (n = 2701; standardized prevalence ratio [SPR] = 0.00; 95% confidence interval [CI]: 0.00-0.55). Prevalence of advanced adenoma was also much lower among subjects who had previous colonoscopies (SPR = 0.42; 95% CI: 0.25-0.68). Adjusted prevalence ratios (95% CIs) for detecting an advanced adenoma were 0.38 (95% CI: 0.16-0.90), 0.34 (95% CI: 0.15-0.74), 0.38 (95% CI: 0.16-0.90), and 0.53 (95% CI: 0.27-1.04) among participants with a negative colonoscopy conducted 1-5, 6-10, 11-15, and >16 years ago, respectively, compared to participants with no previous colonoscopy.

CONCLUSIONS

The low risk of CRC and advanced adenomas after a negative colonoscopy supports suggestions that screening intervals be extended to > or =10 years.