5th International Cancer Control Congress
What does science tell us about current screening recommendations?
Dr Edward Trapido - LSU Health Science Center, New Orleans, USA
For years the world has revolved around some standard tests for cancer screening and things have changed. So programmes need to change and countries need to change, both Peru and all countries. So in the past, for example, we relied on the Pap smear, well now it turns out that actually testing for HPV, for human papilloma virus, and treating right on the spot with cryosurgery is really the best way to screen for cancer. In fact, there are articles out just today that show that HPV testing and treatment is far better than Pap smears. Pap smears were always considered the standard diagnostic technique if then followed up by the appropriate procedures. Now it turns out even the rate of finding cancer is higher using HPV testing, treating on the spot, removing any tissue that’s affected and actually making a difference. So, first of all, you have to think twice about doing Pap smears.
The second thing is countries are still doing PSA. We’ve known for years that PSA is an ineffective and actually a dangerous test for looking for prostate cancer because it far more often identifies individuals with disease that are not prostate cancer. So these poor men have to go through either removal of the prostate cancer or radiation, all of which are being over-treated for no reason for a disease that’s not going to kill them. So countries should not be doing PSA anymore, there’s no justification.
Now we come to mammography and we have felt all along that mammography was finding more early cancers, treating them earlier and saving more lives. It turns out that in the countries that have been doing mammography, yes they’ve been finding early cancers, but what really probably has been saving their lives is the use of adjuvant therapy which came out at the same time. So now there’s a whole question about whether mammography really is the reason because what we haven’t seen in those countries is a change in late stage disease. You would think if we found all this early stage and treated it successfully then the late stages would start to decrease. That hasn’t happened; they’ve continued to rise. So what’s happened is we’ve found these earlier cases which probably never would have killed people and if they would have they’re being treated with adjuvant therapy and adjuvant therapy is what’s saving their lives. But whether it made any difference that they were discovered at mammogram or whether they were discovered clinically a little later, treated the same way, they would have lived as long. So now I have to say mammography maybe not; Pap smears maybe not; PSA definitely not.
That leaves us with colorectal cancer screening which we still think is very good, although the interval between screens is questionable now. It should be every ten years based on what? We don’t have any information about that. Until what age? We don’t know. So that’s another thing you have to check.
Finally we come to lung cancer. Lung cancer we’ve not been able to do anything for screening. Using sputum doesn’t work; the only thing that seems to work now is for very heavy smokers to undergo spiral CT and in that group there is evidence that cancers are found early. That’s not going to work in poor countries so we have a lot to go.
So the bottom line of that is what we thought we knew about cancer screening and the message we’ve been sending out for thirty years, it’s time to look at it again and apply the evidence to the practice.