Please select the eligibility criteria that correspond to the clinical trial below.
Title: The Nurses' Health Study (NHS) and Health Professionals Follow-Up Study (HPFS) Folic Acid Prevention Trial
Brief Summary: RATIONALE: Chemoprevention is the use of certain substances to keep cancer from forming. The use of folic acid may prevent colorectal cancer.

PURPOSE: This randomized clinical trial is studying how well folic acid works compared with a placebo in preventing colorectal polyps in patients who have had previous colorectal polyps.


Options:
A: DISEASE CHARACTERISTICS:

Inclusion criteria:

* Participated in the Nurses' Health Study (NHS I) or the Health Professionals Follow-Up Study (HPFS) and have had a previous confirmed diagnosis of adenomatous polyp of the colon or rectum
* Plan on having an endoscopy within 4 years after initiation of the trial
* Must release medical records regarding past and any future endoscopies

PATIENT CHARACTERISTICS:

Inclusion criteria:

* Plasma vitamin B12 concentration of ≥ 300 pg/mL or have a vitamin B12 concentration between 200 and 299 pg/mL and a methylmalonic acid (MMA) level ≤ 32 µg/L

Exclusion criteria:

* Diagnosis of cancer other than non-melanoma skin cancer, or early stage breast or prostate cancer
* Diagnosis of homocystinemia
* Diagnosis of pernicious anemia
* Any gastrointestinal disorder that could lead to a vitamin B12 deficiency
* Diagnosis of cirrhosis or pancreatitis
* Diagnosis of epilepsy, Alzheimer's disease, Parkinsonism, and psychiatric disorders that may interfere with normal functioning

PRIOR CONCURRENT THERAPY:

Exclusion criteria:

* No prior gastrectomy, total colectomy, or pancreatectomy
* Other concurrent multivitamins or supplements that contain folic acid (they may take specific supplements, such as A, C, E, calcium, and iron, or antioxidant formula vitamins)
* No concurrent methotrexate or anticonvulsant
B: Inclusion Criteria:

Women were eligible if they were:

* Married
* Nulliparous
* \< 40 years old
* Living in the same household as their husband

Exclusion Criteria:

Women were excluded if they were:

* Pregnant at enrollment
* Planning to move out of the region
* Using iron supplements within the previous 3 months
* Using an implant form of birth control, or had surgery to prevent pregnancy
* Women with a Hb concentration of \< 70 g/L, defined as severely anemic according to WHO definition (5), were excluded from the study and appropriately treated
C: Inclusion Criteria:

1. One neoplastic polyp removed within three months of study entry or within 16 months of study entry if over 1 cm in size or if subject has had a lifetime history of at least two polyps, with the entire large bowel seen by colonoscopy to be free of further polyps within 3 months of entry.
2. An ability and willingness to follow the study protocol, as indicated by the subject's giving informed consent to participate.
3. Good general health, with no severely debilitating diseases or active malignancy that might compromise the patient's ability to complete the study.
4. Anticipated colonoscopic follow-up three years after the qualifying colonoscopy.
5. Age between 21 and 80 years at the time of the intake colonoscopy.
6. For women of childbearing potential, agreement to use effective birth control for the duration of the study.
7. Intent not to take aspirin or aspirin-containing products, NSAIDs or folic acid for the length of the study unless required by a physician.
8. Not randomized previously or currently in a chemoprevention trial, except for the: "Nutritional Prevention of Large Bowel Polyps" Study (Polyps Prevention Study I); and brief participation in the "VA Cooperative Study" with no continuing involvement.

Exclusion Criteria:

1. Invasive carcinoma in any colonic polyp removed.
2. Familial colonic polyposis syndromes.
3. Ulcerative colitis or Crohn's disease.
4. Malabsorption syndrome (e.g. pancreatic insufficiency).
5. Large bowel resection for any reason.
6. Diagnosed narcotic or alcohol dependence
7. Contraindication to aspirin use, including:

   1. documented peptic ulcer disease in the past 20 years
   2. aspirin sensitivity
   3. bleeding diathesis, including hemorrhagic stroke
8. Likelihood of NSAID use

   1. recurring arthritis or other musculo-skeletal problems
   2. frequent NSAID use in 5 years preceding
   3. history of stroke or TIAs
   4. history of angina or myocardial infarction
   5. desire to take aspirin for the prevention of cardiovascular disease
9. Required or contraindicated folic acid use pernicious anemia or folic acid deficiency
10. Pregnancy or lactation.
D: Inclusion Criteria:

* Married women of reproductive age identified as a new pregnancy using a urine test

Exclusion Criteria:

* Menopausal or sterilized woman or currently already pregnant or breastfeeding an infant \<9 months of age

Answer: A