COMMENTARY

Metformin Active in Reducing Colorectal Polyp Recurrence

David J. Kerr, CBE, MD, DSc, FRCP, FMedSci

Disclosures

April 22, 2016

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Hello. I'm David Kerr, professor of cancer medicine from the University of Oxford.

As you know, I've a long-standing interest in the treatment and biology of colorectal cancer. As I've become older, more mature, I've become much more interested in the concept of prevention as well as doing our best in terms of treating those patients that we see regularly in the clinic.

There's a very interesting study that's just been published by a distinguished Japanese group in Lancet Oncology,[1] in which they've looked at the chemopreventive effects of low-dose metformin. Basically, they took patients who underwent resection of polyps/adenomas, and they randomly assigned them to receive a placebo or low-dose metformin, 250 mg daily. The treatment lasted for 1 year, during which they watched over the patients very carefully in terms of side effects—monitoring a whole host of glucose-associated endpoints, including glycosylated hemoglobin—to make sure there were no side effects or problems. After a year's time, there was another endoscopy and they counted the number of polyps/adenomas.

It was a double-blind, prospective, randomized trial, so the whole trial staff was completely blind as to whether the patients received placebo or a single 250-mg tablet of metformin.

What they found at the end of the year—it was a small study; only 150 patients randomized—was that there was a significant reduction in the number of polyps/adenomas in the metformin-treated group: 38% of patients had recurrent adenomas compared with 57% in the placebo group. It's a really interesting result.

There's a lot of mechanistic work going on just now looking at whether metformin has advantageous properties, and what could those be? It has a very interesting effect in adenomas. This is hypothesis-generating, I would say, and should be repeated in a larger prospective trial.

Now there are some really interesting possibilities that we can add to the therapeutic armamentarium for prevention of colorectal cancer. We've talked about low-dose aspirin before.[2] I think vitamin D replenishment could be terribly important,[3,4] and here are some preliminary interesting data on the possibility that nontoxic, low-dose metformin may contribute to that stable. Really, really interesting work, and definitely something that should be taken forward in large, prospective, randomized trials.

As always, I'd be very grateful for any comments you might wish to make or comments you'd wish to post. This is an interesting time in which we live, in terms of balancing our existences as cancer-treating oncologists with the possibility of seeing how we can get involved and engaged in preventive research.

Thanks for listening.

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