Incidence and recurrence rates of colorectal adenomas: a prospective study

Colorectal adenoma characteristics as predictors of recurrence

PURPOSE

The identification of groups with a high risk of colorectal adenoma recurrence remains a controversial issue for clinicians. This study was designed to assess the predictive value of initial patient and adenoma characteristics of the three-year recurrence.

METHODS

The study population was composed of 552 patients with resected colorectal adenomas who completed the European Fiber-Calcium Intervention trial. At both baseline and three-year examinations, the characteristics of adenomas were recorded according to a standardized protocol. The main outcomes measured were the three-year overall recurrence, recurrence of multiple adenomas, recurrence of advanced adenomas (size > or = 1 cm or tubulovillous/villous architecture or moderate/severe dysplasia), and proximal and distal recurrence.

RESULTS

A three-year recurrence was observed in 122 patients (22.1 percent), and more than one-half of them had recurrent adenomas on the proximal colon. After adjustment for patient characteristics and treatment allocation, the number of adenomas and their proximal location at baseline were the main predictors of recurrence. In comparison with patients who had one or two adenomas on the distal colon, patients with three or more adenomas with at least one of them located on the proximal colon had a much higher risk of overall recurrence (5.3; 95 percent confidence interval, 2.7-10.3), proximal recurrence (8.5; 95 percent confidence interval, 4.1-18), and advanced adenoma recurrence (5.5; 95 percent confidence interval, 2.4-12.6).

CONCLUSIONS

Follow-up colonoscopies in patients with adenomas should include careful examination of the proximal colon. The time interval between follow-up examinations could probably be extended beyond three years in patients who have only one or two distal adenomas.

Cost-effectiveness of colorectal cancer screening in the average risk population

Colorectal cancer (CRC) is a leading cause of cancer death in North America and in Israel. Risk of CRC increases exponentially with age starting at the age of 50 years. Therefore, people older than 50 years are being considered as an average risk population for CRC. The objective of this study was to obtain an improved assessment of the cost-effectiveness analysis of screening for CRC in the average risk population by using a more accurate technique, namely the Partially Observed Markov Decision Process (POMDP). We conducted a cost-effectiveness analysis within the specific probability rates and costs in Israel. This study revealed that it is highly cost-effective to screen average-risk asymptomatic individuals.

Surveillance after positive and negative colonoscopy examinations: issues, yields, and use

As colorectal cancer screening gains acceptance by the public, the use of colonoscopy will increase. The frequency of surveillance examinations after detection of an adenoma is one of the largest contributors to the cost of colorectal cancer screening. Ten years after the publication of the landmark National Polyp Study, the issue of when to perform surveillance examinations and how often to expect advanced findings remains acute. Current guidelines for surveillance vary across specialty organizations. Individuals with advanced adenomas are at increased risk for recurrent advanced adenomas. The impact of multiple nonadvanced adenomas or a single nonadvanced adenoma on subsequent risk of an advanced adenoma or cancer is less clear. Still less is known about findings on repeat examinations after an initial negative examination, whether after colonoscopy or sigmoidoscopy. The yield after a negative examination is an important consideration in determining the recommended interval for screening colonoscopy. For example, the data supporting a 10-yr interval for screening colonoscopy is only indirect. What little we do know about the yield after negative examinations comes from selected, nonrepresentative populations. Of concern, evidence from several polyp prevention trials demonstrates higher yields for subsequent cancer than would be expected, despite a relatively high use of surveillance procedures in follow-up. Further population-based research on the frequency of use and yield of surveillance examinations is needed. Studies that examine the need and the needed timing of subsequent surveillance are essential to containing costs for screening as well as to informing the public better about what endoscopic screening can and cannot accomplish.

Molecular validation of the modified Vienna classification of colorectal tumors

Although the Vienna classification has been introduced to resolve discrepancies in histological diagnoses of colorectal tumors between Western and Japanese pathologists, practical applications of this classification scheme have been problematic because invasion of the lamina propria of tumor cells is often difficult to recognize. Therefore, the following refinements of the classification criteria are needed: category 3, low-grade adenoma/dysplasia; category 4, intramucosal borderline neoplasia; 4-a, high-grade adenoma/dysplasia; 4-b, well-differentiated adenocarcinoma; category 5, definite carcinoma; 5-a, intramucosal moderately-differentiated adenocarcinoma; and 5-b, submucosal carcinoma. We attempted to test whether molecular genetic alterations are related to the modified classification scheme and whether they may help to further categorize the various intramucosal neoplasia grades of colorectal tumors. Two-hundred-thirty-two colorectal tumors were examined using flow cytometric analysis of DNA content, polymerase chain reaction microsatellite assays, and single-strand conformational polymorphism assays to detect abnormalities of DNA content, chromosomal allelic loss, and Ki-ras and p53 gene mutations. Microsatellite instability (MSI) was also examined. Frequencies of genetic alterations and DNA aneuploid states increased with an increase in the grade assigned according to the modified Vienna classification. MSI was a rare event in colorectal adenomas and their frequency of MSI did not correlate with tumor grade. The combined genetic and DNA ploidy data support the conclusion that analysis of genetic alterations and DNA aneuploid states may help in appropriate categorization of colorectal tumors according to the modified Vienna scheme. In addition, MSI-positive tumors may represent a specific subtype of colorectal adenomas.

Colorectal polyps in the elderly: what should be done?

Colorectal cancer is an important cause of morbidity and mortality among Western nations, and is more common in the elderly than in younger individuals. With the general acceptance of the adenoma-carcinoma sequence, the current consideration is that colorectal cancer is preventable if all adenomas are removed before they have the chance to progress to cancer. To that end, physicians should now advocate screening for colorectal cancer and through this effort a large number of patients with adenomatous polyps will be discovered. It is important to understand the strategy in dealing with this growing population of patients with adenomas. After an initial polypectomy, patients with adenomas should be entered into a surveillance program to detect and remove recurrent adenomas. Recommended surveillance intervals are shorter for patients with a family history of colorectal cancer, those with multiple adenomas (>2), large adenomas (> or = 1cm), or those whose adenomas have high-grade dysplasia, villous architecture, or that are cancerous. Effective chemoprevention would be a potential method of lengthening colonoscopic surveillance intervals. Unfortunately, no treatment has been found to be effective enough to alter our current surveillance practice. The only recommendation that can be made at this time for those patients with a history of colonic adenomas is to add 3 g/day of calcium carbonate to their diet, though its effect on adenoma recurrence is modest.

Fibres and colorectal cancer: should we change our dietary advice on prevention?

Evidence from epidemiological studies overwhelmingly indicates that fruit, vegetables and cereals prevent cancer at a wide range of sites in the body, not just the large bowel. However, recent important papers have shown that an intervention diet rich in fruit, vegetables and fibre failed to decrease the risk of new colorectal adenoma formation. The adenoma-cancer sequence and the role of diet are discussed in the light of these new findings.

New occurrence and recurrence of neoplasms within 5 years of a screening colonoscopy

OBJECTIVE

The fear that colorectal adenomas were missed on initial colonoscopy or that new adenomas have developed is often a rationale for repeating a colonoscopic examination. The aim of this study was to delineate risk factors associated with recurrence of colorectal adenomas after an initial baseline screening colonoscopy.

METHODS

The study population comprised 875 subjects who underwent a baseline screening colonoscopy followed by a second examination 1-5 yr later. Multiple logistic regression was used to assess the influence of potential risk factors on the occurrence or recurrence of colorectal adenomas, the strength of the influence being expressed as an OR with a 95% CI.

RESULTS

Colorectal adenomas were detected in 484 of all patients (55%) at baseline colonoscopy. Within a 1- to 5-yr time interval, 181 patients (37%) had recurrent adenomas (adenomas were removed during the first colonoscopy) and 73 patients (19%) had newly developed adenomas (adenomas were absent on the first colonoscopy). The occurrence of adenomas at baseline screening colonoscopy was the only factor associated with an increased risk for the recurrence of adenomas at follow-up (OR = 2.51, 95% CI = 1.77-3.55). Recurrence was associated with multiple baseline adenomas (4.45, 2.98-6.64) and baseline adenomas larger than 1 cm (2.62, 1.99-3.11). Recurrence was not associated with histology type or family history of colorectal cancer. There was a significant trend for adenomas to recur in the same proximal or distal segment as the baseline adenomas (p = 0.02).

CONCLUSIONS

Colon adenomas tend to recur with greater frequency if the adenomas removed at baseline were either large or multiple. Although patients with large adenomas or multiple adenomas at baseline screening colonoscopy are at a 2.6- to 4.5-fold risk for recurrence of adenomas, the rate of de novo adenoma formation in patients without baseline adenomas may be large enough to warrant repeat colonoscopy at some time in the future. The exact timing of the follow-up colonoscopy needs to be determined.

The effect of attending a flexible sigmoidoscopic screening program on the prevalence of colorectal adenomas at 13-year follow-up

OBJECTIVES

Understanding the epidemiology of colorectal adenomas is a prerequisite for designing follow-up programs after polypectomy. The aim of the study was to investigate the effect of polypectomy on the long-term prevalence of adenomas.

METHODS

In 1983, a total of 799 men and women aged 50-59 yr were drawn from the general population register. Of these, 400 comprised a screening group and 399 a matched control group. The screenees were invited to undergo a once-only flexible sigmoidoscopy. Persons with polyps had a baseline colonoscopy with follow-ups in 1985 and 1989. In 1996, both the screenees and the controls were invited to a colonoscopic examination.

RESULTS

In 1996, a total of 451 (71%) individuals attended. Adenomas were found in 78 (37%) individuals in the screening group and 103 (43%) in the control group, relative risk (95% confidence interval): 0.9 (0.7-1.1), p = 0.3, and high-risk adenomas (severe dysplasia, adenomas > or = 10 mm, villous components) were found in 16 (8%) and 32 (13%), respectively; relative risk (95% confidence interval): 0.6 (0.3-1.0), p = 0.07.

CONCLUSIONS

There was no significant difference in adenoma prevalence between the group after the screening program and the controls after the usual care. There was a trend toward more high-risk adenomas in the control group. This suggests a very limited effect of one-time screening sigmoidoscopy with surveillance colonoscopy on the prevalence of adenomas, but a preventive effect on the development of high-risk adenomas consistent with the reported effect on cancer prevention.

Incidence and recurrence rates of colorectal adenomas in first-degree asymptomatic relatives of patients with colon cancer

OBJECTIVES

Subjects with one first-degree relative affected with colorectal cancer are considered to be at increased risk of colorectal adenomas. We compared the recurrence and incidence rates of colorectal adenomas among subjects with one first-degree relative with colorectal cancer and those without family history.

METHODS

A series of consecutive asymptomatic subjects successfully underwent a colonoscopy, were found to have either normal results or at least one adenoma, provided a detailed family history, and were offered a second colonoscopy 3 yr later; 190 out of 436 subjects accepted, 134/172 with one or more adenomas and 56/264 with no abnormalities at the initial examination. A first-degree family history was reported by 43/134 and 26/56, respectively.

RESULTS

By multivariate analysis, the presence of adenomas at follow-up examination was significantly associated with a positive family history of colorectal cancer in both subgroups, those with a previously resected adenoma (odds ratio = 2.23, 95% CI = 1.04-4.79) and those without (odds ratio = 8.95, CI = 1.29-62.22).

CONCLUSION

A history of one first-degree relative with colorectal cancer is associated with a significant increase in 3-yr cumulative incidence and recurrence rates of adenomas.

Adenoma characteristics as risk factors for recurrence of advanced adenomas

BACKGROUND AND AIMS

The link between adenoma characteristics at baseline colonoscopy and adenoma recurrence is poorly understood. We assessed whether the number, size, location, or histology of resected adenomas was related to the probability of recurrence of advanced lesions.

METHODS

Analyses were based on 1287 men and women in the wheat bran fiber (WBF) study, a randomized, double-blind trial of WBF as a means of decreasing the probability of adenoma recurrence over a period of 3 years. Multiple logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Recurrence of advanced adenomas (>1 cm or tubulovillous/villous histology) was higher among individuals with adenomas >1 cm compared with those with adenomas <0.5 cm (OR, 2.69; 95% CI, 1.34-5.42) and among those with proximal than those with distal adenomas (OR, 1.65; 95% CI, 1.02-2.67). No association was observed for adenoma number or histology. A shift in location from the distal colon and rectum at baseline (54.6%) to more proximal recurrent adenomas (45.2%), including advanced lesions (42.8%), was observed.

CONCLUSIONS

Large or proximally located adenomas are important indicators of recurrence of advanced lesions. Because most recurrences were detected in the proximal colon, careful surveillance of this area is warranted.

Endoscopic treatment of colorectal benign-appearing lesions 3 cm or larger: techniques and outcome

PURPOSE

Colonoscopic polypectomy is the preferred technique to remove the majority of polyps. The authors evaluate feasibility, safety, and the effectiveness of endoscopic treatment of colorectal benign-appearing polyps equal to or larger than 3 cm.

METHODS

Ninety-seven patients with 104 giant polyps underwent polypectomy within a nine-year period. The majority of these procedures were performed on an outpatient basis, all on unsedated patients. Gross appearance, size, location, histologic characteristics, synchronous lesions, modality, and adequacy of removal of giant polyps were analyzed. The follow-up was achieved in 89 percent of patients during a period ranging from 6 to 96 months (median, 38).

RESULTS

Of the 104 removed polyps, 75 (72 percent) were adenomatous, 2 (2 percent) were hyperplastic, and 27 (26 percent) were malignant polyps. Six patients had more than one giant polyp. Several additional smaller polyps were found in 52 patients and a synchronous cancer in 4. Twenty-one (20 percent) giant polyps were equal to or larger than 4 cm. Forty-nine were pedunculated, 20 were short-stalked, and 35 were sessile. Sixty-one polyps were excised in one piece, and forty-three were excised using a piecemeal technique. Only four complications (3.8 percent) were recorded; all cases were treated endoscopically. Fifty-eight (75 percent) adenomas and eighteen (67 percent) malignant polyps were completely excised. Surgery was performed in 7 of 27 patients (27 percent) with malignant polyps, where there was a doubtful, infiltrated margin or poorly differentiated cancer. Postpolypectomy surveillance permitted the detection and treatment of 25 metachronous or recurrent polyps and a metachronous cancer.

CONCLUSIONS

This study shows that polypectomy of giant colorectal polyps, performed by an expert endoscopist, is feasible, effective, and safe, even on an outpatient basis. The authors confirm that malignant polyps with incomplete excision, lymphovascular invasion, and poor differentiation require bowel resection. Postpolypectomy surveillance is useful for all patients who have undergone colonoscopic resection of giant adenomatous or malignant polyps.

Dietary advice on cancer prevention: time for a change?

Media coverage of recent dietary intervention studies has cast doubt on dietary advice for cancer prevention. The studies cited focussed on colorectal adenoma initiation as opposed to progression. There is ample evidence that in the colorectum the factors controlling initiation of adenomas differ from those causing progression to cancer, and that it is the latter that are the most important. In the light of this it is argued that studies of adenoma initiation are irrelevant to the advice given for overall cancer prevention.

A multi-stage model of adenoma development

The overwhelming proportion of colorectal carcinomas are believed to originate as adenomatous polyps (adenomas), and the identification and removal of adenomas is an important component of colorectal cancer prevention efforts. Mathematical modeling of adenomas can increase our understanding of the natural history and biology of adenomas and colorectal cancer and can help in the effort to devise optimal prevention and screening strategies. Here we adapt the multi-stage model of carcinogenesis to the problem of the development and growth of adenomas. We show that, using plausible values for the biological parameters, the model can fit various aspects of adenoma data including adenoma prevalence by age, the size distribution of adenomas, clustering of adenomas within individuals and the correlation between distal and proximal adenomas. Explaining the clustering of adenomas within individuals, as well as other findings, requires heterogeneity in risk in the population; we show how such heterogeneity can be related to the distribution of biological parameters in the population. The model can also be adapted to account for adenoma development in two major syndromes related to colorectal cancer, familial adenomatous polyposis and hereditary non-polyposis colorectal cancer.

Polypectomy may be adequate treatment for adenoma-like dysplastic lesions in chronic ulcerative colitis

BACKGROUND & AIMS

Chronic ulcerative colitis (CUC)-associated adenoma-like DALMs (dysplasia-associated lesions or masses) pose a difficult clinical problem to both gastroenterologists and pathologists because they are difficult to distinguish endoscopically and pathologically from sporadic adenomas that develop coincidentally in patients with CUC. The aim of this study was to evaluate the outcome of CUC patients with an adenoma-like DALM treated conservatively and to compare the findings with CUC patients with a coincidental sporadic adenoma.

METHODS

Clinical, endoscopic, and pathological features and outcome of 24 CUC patients with an adenoma-like DALM were compared with those of 10 CUC patients with a coincidental sporadic adenoma and 49 non-CUC (control) patients with a sporadic adenoma. Patients were followed up for a mean of 42.4 and 41.2 months for the 2 CUC groups, respectively, and 37.0 months for the non-CUC controls by endoscopic surveillance.

RESULTS

Of the 24 CUC patients with adenoma-like DALMs (male/female ratio, 14/10; mean age, 61.5 years; mean duration of colitis, 10.4 years), 14 (58%) developed further adenoma-like DALMs within the follow-up interval. Only 1 patient (4%) developed an isolated focus of low-grade dysplasia, and none developed adenocarcinoma. Five of 10 (50%) CUC patients with sporadic adenomas developed further adenomas, and none of the patients in this group developed either dysplasia or adenocarcinoma. Of the 49 non-CUC control patients, 39% developed further adenomas.

CONCLUSIONS

CUC patients who develop an adenoma-like DALM that endoscopically and histologically resembles a sporadic adenoma, regardless of its location (either within or outside areas of documented colitis), may be treated with polypectomy and endoscopic surveillance because of its relatively benign course.

Management of Malignant Mucinous Adenomas

Background

Malignant polyps are defined as adenoma with cancerous tissue penetrating into or through the muscolaris mucosae in the submucosa, and endoscopic removal is the most common treatment for such polyps. In the presence of malignant mucinous adenoma, defined as a malignant adenoma in which a significant amount of mucus is present in the stroma, the therapeutic approach is controversial and authors have performed surgical resection in all cases. The purpose of the study was to demonstrate that malignant mucinous adenoma is not a condition suggesting by itself a bowel resection.

Methods

Ten patients with malignant mucinous adenoma were enrolled in the study: endoscopic treatment alone was performed in 4 cases, and polypectomy was followed by surgical resection in 6 cases.

Results

At a median follow-up of 74.2 months no distant metastases had occurred in any of the patients treated with endoscopic polypectomy alone; during the follow-up, 1 patient had a local recurrence and surgical resection was performed. Only one case of residual disease was found at histology among the patients in which endoscopic polypectomy was followed by surgical resection. No complications occurred after endoscopic treatment in any case.

Conclusions

In the absence of unfavorable histologic parameters, malignant mucinous adenomas should be managed with the same criteria of other malignant adenomas, and endoscopic polypectomy is considered as a safe and effective treatment when radicality criteria are fulfilled.

Novel germline APC variants in patients with multiple adenomas

Chain-terminating germline APC mutations are responsible for adenomatous polyposis coli (APC). In the present work, we tested the hypothesis that germline APC mutations may be present in some patients with a milder phenotype, i.e., multiple synchronous colorectal adenomas. Eighteen patients with 3 or more colorectal adenomas at endoscopy (within a 6-month period) were ascertained from a series of subjects undergoing endoscopic examination. Their blood DNAs were analysed for the presence of germline mutations in the APC coding region by single-strand polymorphism analysis. Ten unrelated polyp-free subjects and 101 unrelated APC patients were used as controls in the molecular analyses. Five of the eighteen patients carried novel germline APC variants or rare polymorphisms. These were various in site (from the splice acceptor site of intron 7 to the end of exon 15) and type (splice-site, missense, and chain-terminating mutations). Only one of ten polyp-free individuals carried a silent APC variant and none of these variants was found in the 101 APC controls. A first- or second-degree family history of colorectal cancer was reported by 4 of the 5 patients carrying a germline APC variant. In conclusion, novel APC germline variants were detected in patients with multiple synchronous adenomas. This suggests that the development of sporadic adenomas, in some instances, is associated with the presence of minor germline variants of the APC gene and that the spectrum of germline APC functional mutations may be larger than previously thought.

Predicting the risk of metachronous colorectal cancer in patients with rectosigmoid adenoma using quantitative pathological features. A case-control study

The prognostic value of quantitative pathological features in rectosigmoid adenomas was investigated, in search of more precise identifiers of adenoma-bearing patients at high risk of metachronous colorectal cancer. In a "nested case-control study" design, 21 cases with metachronous colon cancer during an average follow-up time of 16 years (range 3-30 years) after polypectomy and 67 controls were selected from a cohort of 1618 patients. The most advanced adenoma of each patient was analysed. Cases were matched with up to three controls simultaneously for size, grade of dysplasia, histological type, and number of adenomas, as well as for duration of follow-up. The patients did not undergo any post-polypectomy surveillance. Geometric characteristics of tumour nuclei, the arrangement of nuclei in the epithelium, and glandular changes were measured, and mitoses were counted. Several quantitative features measuring nuclear polymorphism and crowding showed significant prognostic value, while those measuring glandular changes and mitotic activity did not. A multivariate combination of the average distance between nuclei and the standard deviation of nuclear area discriminated an unfavourable group (n = 44) with 17 metachronous cancers from a favourable group (n = 44) with four metachronous cancers (P = 0*001, RR = 6*3). With the optimum cut-off, 28 patients without any metachronous cancer were discriminated from a group of 60 patients with 21 metachronous cancers. In conclusion, in the present study, quantitative pathological features assessed in rectosigmoid adenomas showed prognostic value additional to traditional measures. These features may therefore be useful in guiding post-polypectomy surveillance.

Initial management and follow-up surveillance of patients with colorectal adenomas

The clinical management of patients with adenomas is interesting because of the adenomas' malignant potential, the availability of effective intervention by colonoscopy, and the increasing number of patients having adenomas detected and removed. The current literature on follow-up surveillance is reviewed, and surveillance intervals are suggested based on data from the National Polyp Study. Patients newly diagnosed with three or more adenomas, an adenoma of more than 0.5 cm, or with a family history of colorectal cancer should have surveillance colonoscopy at 3 years following the polypectomy. Surveillance of patients with single, small tubular adenomas can be extended to 5 or more years. Patients with large sessile or malignant adenomas need to have follow-up earlier. Identification and removal of adenomatous polyps have been shown to reduce colorectal cancer incidence.

Leisure and occupational physical activity and risk of colorectal adenomatous polyps

Multiple studies have shown a protective effect for physical activity on the incidence of colorectal cancer, but few have addressed its association with incident adenomas and none have investigated its association with metachronous adenomas. We interviewed 2,001 patients undergoing colonoscopy in 3 New York City practices between 1986-1988. Of these, 298 had a first diagnosis of adenomas, 506 had normal colonoscopies, 197 had metachronous adenomas and 345 had normal colonoscopies with a past history of adenomas. Subjects were queried regarding use of moderate amounts of recreational exercise (swimming, jogging, biking, racket sports and other sports) on a regular basis, and were also asked to estimate their level of physical activity. Occupational physical activity was assessed through a blinded coding of occupational titles. After adjusting for age, years of education, body mass index, total caloric intake, dietary fiber intake, dietary fat intake and years of cigarette smoking, protective effects of borderline significance were observed among males for leisure physical activity for metachronous and incident cases. Occupational physical activity was found to be significantly protective in male incident cases. Men with increased levels of either occupational or leisure activity showed a reduction for incident and metachronous cases. No effects were observed for females. Thus, in this study, both leisure and occupational physical activity were associated with a reduced risk of incident and metachronous adenomas among men but not women.

The effect of calcium and vitamin supplements on the incidence and recurrence of colorectal adenomatous polyps

BACKGROUND

Recent attention has focused on calcium and certain vitamins as potential protective agents against colorectal neoplasia.

METHODS

Two case-control studies were conducted on patients who underwent colonoscopy between 1986 and 1988, comparing 297 patients with newly diagnosed adenomas with 505 controls (without current or prior history of neoplasia), and 198 patients with recurrent adenomas with 347 recurrent controls (with no current neoplasia, but with a history of polypectomy). Subjects were interviewed regarding their regular usage of supplementation with vitamins A, C, D, and E, or with calcium, multivitamins, or any vitamin supplements.

RESULTS

No consistent associations were observed with the use of any of these supplements.

CONCLUSIONS

More studies are necessary to confirm these findings. It may be necessary to develop other chemopreventive agents, such as aspirin, for colorectal neoplasia.

Reproductive risk factors for colorectal adenomatous polyps (New York City, NY, United States)

Events of reproductive life, such as parity and age at menarche, have been found in some but not all studies to be associated with risk for colorectal cancer in females. Because adenomatous polyps (adenomas) are precursors of colorectal cancer, we investigated whether reproductive variables were associated with colorectal adenomas. We conducted a case-control study among patients examined in three colonoscopy practices in New York City (NY, United States) from 1986 to 1988. Adenoma cases (n = 128) were defined as women who had an adenoma detected at the index colonoscopy with no history of inflammatory bowel disease, adenomas, or cancer. Controls (n = 283) were women with a normal index colonoscopy and no history of inflammatory bowel disease, adenomas, or cancer. The adjusted odds ratio (OR) for the association of early menarche (age less than 13 years) with adenomas was 0.6 (95 percent confidence interval = 0.4-0.9). Parity, history of spontaneous or induced abortion, infertility, type of menopause, age at menopause, use of oral contraceptives, and use of menopausal hormone replacement therapy were not associated statistically significantly with adenoma risk, although some possible trends were observed. Our findings do not implicate reproductive events, nulliparity, or overexposure to estrogens or to menstrual cycles as mechanisms of increased risk for colorectal neoplasia.