The study was conducted from September 1993 to July 2001. Subjects were identified and recruited from the Johns Hopkins Polyposis Registry. Written informed consent was obtained from all subjects or their parents, and assent was obtained from subjects under 18 years of age. The protocol was approved by the Johns Hopkins Joint Committee on Clinical Investigation (the institutional review board).
The genotypic and phenotypic status of all potential subjects was assessed to determine their eligibility for the trial. All potential subjects and their parents (in the case of minors) received genetic counseling before undergoing genetic testing for APC
Eligible subjects were older than eight years of age and had a disease-causing mutation of the APC
gene but had no endoscopically detectable colorectal adenomatous polyps and no history of colonic surgery.
The following were reasons for exclusion from the study: use of an NSAID or aspirin for more than one week in the three months preceding the study, unwillingness to discontinue taking NSAIDs, absence of the use of effective birth control in girls and young women of childbearing age, pregnancy, a white-cell count of less than 4000 per cubic millimeter, a platelet count of less than 100,000 per cubic millimeter, a blood urea nitrogen level of more than 25 mg per deciliter (8.9 mmol per liter), a serum creatinine level of more than 1.5 mg per deciliter (132.6 μmol per liter), a history of peptic ulcer disease or gastrointestinal hemorrhage, a history of cancer, active bacterial infection, use of dimethyl sulfoxide, a history of aspirin allergy, or a body weight of less than 20 kg.
The sponsor generously supplied both sulindac and placebo but was not otherwise involved in the design or conduct of the study. Data were held by the principal investigator.
Forty-one eligible subjects entered this double-blind, placebo-controlled trial. They were randomly assigned to receive sulindac orally twice a day for four years or identical-appearing placebo tablets. The sulindac dose was calculated on the basis of body weight and adjusted according to changes in weight during the course of the study. The 11 subjects in the sulindac group who weighed 20 to 44 kg at the beginning of the study received 75 mg of sulindac orally twice a day, and the 10 who weighed more than 44 kg took 150 mg of sulindac twice a day. By the end of the study, all but three subjects were receiving the higher dose. Compliance with treatment was assessed by means of pill counts, review of subjects’ diaries, and telephone calls every other week.
The development of rectosigmoid adenomatous polyps was assessed by sigmoidoscopy with an Olympus flexible video sigmoidoscope. One investigator, who did not review the records of previous examinations, made all the assessments. Evaluations were performed before treatment with sulindac or placebo was begun (month 0) and every 4 months after treatment was initiated, for a total of 48 months. At each examination, the endoscopist counted the total number of polyps in the circumference of the colorectum from 20 cm to the anal verge, and the examination was recorded on videotape. The diameter of up to five polyps just distal to 20 cm was measured in millimeters with a graduated scale passed through the biopsy channel of the sigmoidoscope. These measurements were averaged to determine the mean size of each subject’s polyps.
Evaluation of Safety
Adverse effects were monitored by means of telephone interviews every two to four weeks and at each four-month visit. A complete blood count was obtained and levels of glucose, blood urea nitrogen, serum creatinine, serum electrolytes, and bilirubin were measured at each visit. Adverse events were graded in accordance with the Common Toxicity Criteria of the National Cancer Institute.16
On this scale, a score of 0 indicates no adverse effects and a score of 5 life-threatening effects.
Measurement of Prostaglandin Levels
Biopsy specimens of the rectal mucosa were obtained before the initiation of treatment (month 0), at four months, and at one, two, three, and four years with standard biopsy forceps through a flexible sigmoidoscope. Tissue specimens were obtained from the normal-appearing mucosa 20 cm from the anal verge, snap-frozen in liquid nitrogen, and stored at −70°C until further analysis. Specimens were coded to disguise the subjects’ treatment assignment, and the levels of prostaglandin D2
, prostaglandin E2
, prostaglandin F2α
, thromboxane B2
, and 6-keto-prostaglandin F1α
, the principal metabolite of prostacyclin, were measured by gas chromatography–mass spectrometry as described previously.12,13
The level of each prostaglandin was determined on the basis of the inclusion of known quantities of deuterated prostaglandins as internal standards. All levels of prostaglandin were adjusted for the quantity of protein in the sample.
The primary outcome variables were the number and the size of polyps in the sulindac and placebo groups at 48 months or at the time of withdrawal from the study. Student’s t-test was used to compare the two groups according to the intention-to-treat principle. The sample size was calculated to provide the study with 80 percent power to detect a difference of 1 SD in the number of polyps between groups (a two-sided alpha of 0.05).
To determine whether the treatment assignment was associated with the outcome and predictor variables, we constructed random-effects linear longitudinal models.17
These models allowed us to compare the treatment groups while adjusting for the number and the size of polyps in the same patient over time. In contrast, the t-test compares mean values at a fixed point in time. In addition, the longitudinal model assesses the simultaneous effects of treatment group, time, and noncompliance with the assigned therapy. We assumed that the longitudinal effects within subjects were random, thus essentially devising a time trend for each subject. To fit the model, the raw data had to be transformed, which made the estimated coefficient difficult to interpret clinically. Therefore, we have provided estimates of the difference between groups at the end of treatment. We fitted two series of random-effects linear longitudinal models for each of the two outcomes (the number and the size of polyps); the covariates were time (in months), an indicator of early withdrawal from the study, and the treatment group. Interactions between covariates were evaluated and retained in the model if they were significant. All analyses were performed with the use of Stata software version 6.0.18
Secondary end points were the occurrence of polyps, the histologic features of polyps (tubular, tubulovillous, or villous), and the side effects of sulindac. We used Fisher’s exact test to determine whether these variables were associated with the treatment assignment.
We used Student’s t-test to compare the differences in the mean percent change in prostaglandin levels from base line in the sulindac group and the placebo group and in subjects in the sulindac group in whom polyps developed and those in the sulindac group who were free of polyps. The mean percent change was calculated as the mean of prostaglandin levels at four months and one, two, three, and four years divided by the base-line prostaglandin level.
All P values were two-sided. We also used nonparametric tests in the place of t-tests and confirmed the results.