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Bowel cancer prevention pill? -

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Staying with cancer prevention, it is known that some drugs may reduce the risk of certain cancers, it's called chemoprevention, and the evidence is strongest in bowel or colorectal cancer. A research group at the University of California, San Diego, has brought all the available studies together to see which medication might be best. Siddarth Singh is in the division of gastroenterology at the University of California, San Diego.

Siddarth Singh: The most commonly studied medication has been aspirin. The other medications that have been looked at are calcium, vitamin D, folic acid, the non-steroidal medications like celecoxib. And all of these medications have been used in combinations too.

Norman Swan: We should just talk about the people that you are trying to treat here, because it's not just people off the street, it's people who have already got polyps or had cancer.

Siddarth Singh: Correct. We wanted to target a relatively higher risk population, a subset of people who have previously had polyps or colorectal cancer and are at higher risk for recurrence of those polyps or development of cancer.

Norman Swan: There hasn't been any so-called head-to-head trials where they've compared these drugs to each other, you then had to go and make some inferences from studies that had already been done of these drugs individually.

Siddarth Singh: Correct.

Norman Swan: So when you brought together the international evidence from the available trials, and I think that when you added it all up it was about 12,000 people, what did you find?

Siddarth Singh: We found that the non-steroidal medications such as celecoxib seemed to perform really well and decrease the risk of high risk polyps by about 63% over the next 3 to 5 years. However, from a safety standpoint these medications were also associated with a high risk of serious events like hospitalisation, bleeding risk. So perhaps not applicable to every patient who is at risk for recurrence of polyps, but may be considered for the highest risk patients. There needs to be a more nuanced decision of risk and benefit. Contrast what we found, that low dose aspirin is fairly effective in decreasing the risk of serious polyps, at the same time it's also a very safe option.

Norman Swan: And what about the others, folic acid, vitamin D and so on, did they have any effect on preventing?

Siddarth Singh: There was not much that stood out in terms of folic acid by itself or combined with other strategies. And the same thing for vitamin D. There was some suggestion that calcium may decrease the risk of all types of polyps, not necessarily the high risk polyps, but there were also some safety signals which were a little surprising with calcium. So overall we did not think that calcium would be a good strategy for the prevention of high risk polyps.

Norman Swan: So did you find what the people who had been looking at calcium for osteoporosis have found, which is a higher risk of heart attack?

Siddarth Singh: Yes.

Norman Swan: Let's just come back to the non-steroidal anti-inflammatory drugs. So you talk about celecoxib, which we talked about a couple of weeks ago on the Health Report, trade name Celebrex. That's one kind of non-steroidal but the more common ones and the cheaper ones you can get over the counter are things like ibuprofen or naproxen. Were they just as effective as the newer forms of anti-inflammatories in preventing colon cancer?

Siddarth Singh: That's a good question. The trials that were included have basically studied celecoxib and another type of non-steroidal called sulindac. They haven't necessarily studied the non-specific what they call the COX-1 and COX-2 inhibitors which is ibuprofen and Naprosyn. I suspect the beneficial effects are going to be similar, but the safety profile from a bleeding risk standpoint may be higher with the non-selective.

Norman Swan: So the bottom line is if you've got polyps or you've had bowel cancer and you want to prevent a recurrence or the polyp progressing to cancer, then low dose aspirin is just safest option, that's like 75 or 100 milligrams a day. What about the person who…they may have a bit of a family history of colon cancer, bowel cancer, and they are thinking, well, why don't I just take low-dose aspirin every day for cancer. A lot of doctors do that. What's your view on that?

Siddarth Singh: Sure. So there's a lot of accumulating data on aspirin having a chemopreventive effect, not just against colorectal cancer but other cancers too.

Norman Swan: So Dr Singh, are you taking low-dose aspirin?

Siddarth Singh: I haven't started yet. I'm still in my 30s, but as soon as…I asked my dad to start taking it. I would also emphasise that colonoscopies for continued surveillance is important. This strategy does not necessarily replace that part, but it's probably in combination in the sense somebody who has had high risk polyps shouldn't just rely on aspirin for prevention which would also continue on colonoscopies based surveillance.

Norman Swan: Siddarth Singh is in the division of gastroenterology at the University of California, San Diego. And if you're confused about this colonoscopy story, this is when you've had cancer or polyps and the colonoscopy is for follow-up.