Dear Dr. Roach: I am a 71-year-old male who is a nonsmoker and a social drinker. Other than a statin, I am not taking any medications. I have been getting colonoscopies every five years as each time several benign polyps have been found. When I was 67, a couple of precancerous polyps were found along with some benign ones. Because of this, my next colonoscopy was scheduled for three years later.

That procedure, which was performed last year when I was 70, only revealed one benign 3-mm polyp, so the doctor recommended a seven-year wait for my next colonoscopy. Through their patient portal, I expressed concern that given my history showing precancerous polyps within a five-year interval, I’m unsure if it would be wise to wait seven years. Their response was that seven years is the protocol when only one benign polyp is discovered. What is your take on this?

— D.M.

Answer: A colonoscopy is both a screening tool for cancer and a way to prevent cancer by removing polyps before they can get advanced enough to turn into cancer (let alone spread). The major risk factors for a polyp to become cancerous are the size and type of polyp. Polyps less than 10 mm are considered small, and yours is really quite small.

People with small polyps like yours are at a low risk for developing colon cancer, so the recommendation by the task force is for a 7-10 year follow-up. Your doctor chose the lower part of this range, probably because of your previous history and level of concern.

In addition to getting recommended screening tests, there are other ways to reduce your cancer risk. Regular exercise reduces cancer by about 27% in observational studies. A diet high in fruits and vegetables (5 servings a day or so) also reduced the risk of colon cancer by about 25%. Fatty (nonfried) fish had an additional benefit in some but not all studies.

Statin drugs, incidentally, may have a protective effect on colon cancer, but the data are not clear.

Dear Dr. Roach: My 43-year-old son says ivermectin is how he would cure cancer. Is there any research on this?

— P.Z.

Answer: Ivermectin is a critically important drug in the treatment of some parasites, such as hookworm, scabies and strongyloides. Because it also has anti-inflammatory properties, it is sometimes topically used in the treatment of rosacea. Ivermectin was studied for use in COVID-19 infections, but the enthusiasm from promising papers early in the pandemic waned after high-quality evidence didn’t show a benefit.

Ivermectin has been studied for anticancer action in laboratory cell cultures. Although there is some potential, it will be years before the action of ivermectin in cancer cells will be well-characterized. Because ivermectin is already an approved drug and relatively nontoxic at appropriate doses, it could enter clinical trials much faster than a brand-new drug. Unfortunately, most drugs that show promise in the lab do not ever become useful cancer treatments, but there is certainly ongoing research on ivermectin for cancer.

Cancer consists of many diseases, and there isn’t going to be a single simple cure. I strongly urge a person not to take ivermectin to treat or prevent cancer. Instead, get involved in a clinical trial if you want to help medical science advance.

Contact Dr. Roach at ToYourGoodHealth@med.cornell.edu.