How useful is cancer screening?
Herman Kattlove is a retired medical oncologist. He was a medical editor for the American Cancer Society where he helped develop much of the information about specific cancers that is posted on the website at [url]www.cancer.org[/url]. He retired from the ACS in November, 2006.
How useful is cancer screening?
Well, if you ask around, most people think it is pretty effective. In the Journal of the National Cancer Institute, researchers from Europe published some numbers on what people think. They asked residents of several European countries how effective they think are mammography screening for breast cancer and PSA testing for prostate cancer. Specifically, if 1000 people were screened on a regular schedule, how many lives would be saved?
On average, most thought that around 50 lives would be saved for every 1000 person screened for either cancer. Not even close. The real numbers are these: If 1000 women over age 50 are screened for breast cancer every year, one life would be saved. This number would be lower if the women were younger (breast cancer occurs much less often in young women). Still, one life is important and this isnít a bad outcome, even if many of the screened women have to undergo biopsies for spots on the mammogram that turn out not to be cancer.
The results of screening for prostate cancer are even less spectacular. Maybe one out of 2000 men who are between age 59 and 70 and screened regularly will be saved at the end of 10 years. But remember, this is a disease of old men and that guy who is saved will probably not last that much longer anyway. And here, there is a much bigger problem. A lot of men will undergo biopsy (not fun) and many will have prostate cancer that will never spread and kill. Still, they will receive treatment that can leave them incontinent (unable to hold their urine Ė think diapers) and impotent (Viagra usually wonít help). But their lives wonít be saved because prostate cancer isnít very dangerous and lots of other disease can take them away before the prostate cancer does.
And just this week, another potential screening test was thrown into doubt. Remember all the excitement about screening for lung cancer with CT scans. Well, it doesnít work. A new study, from Italy, was just published in the American Journal of Respiratory and Critical Care. The Italian researchers studied men who had smoked at least one pack a day for 20 years. Half received CT scans and the other half didnít. After 3 years, on average, the death rate from lung cancer was the same in both groups. More cancers were found in the screened men, but no fewer deaths. This is the same result that was found 30 years ago when smokers were screened with chest x-rays. More cancers were found, but no more lives saved. No one knows why Ė perhaps some of the small cancers found on x-ray might have gone away spontaneously.
Now I firmly believe that screening for cervical cancer (pap smear) is worthwhile. It finds early precancerous and cancerous changes that can be easily treated. Likewise Iím for colonoscopy or other ways to screen for colorectal cancer (although there arenít good studies proving this actually does save lives).
So mammography is probably OK if you are older than 50, pap smears and colonoscopy for the proper age groups (younger women for paps and people older than 50 for colonoscopy). But screening for prostate cancer is probably not helpful for most. And getting a CT scan to screen for lung cancer is probably useless.
So stop smoking and lead a healthy life. This is more important than all the screening in the world.
Gregory D. Pawelski