For many, cancer screening has obvious appeal. Detecting the disease through screening will generally mean an earlier diagnosis, and earlier treatment should, by rights, lead to better outcomes. Well, that the theory anyway. In practice, though, we know that screening is most certainly not as effective as we might imagine.
For example, mammography has been shown to be quite ineffective as a life-saver, and also subjects women to radiation. Many women with suspicious mammograms go on to have further investigations and treatment that are not without risk (and are stressful too). A significant number of women end up being treated for cancer that would not have harmed for killed them anyway. See here, here and here for blog posts about mammography that might cause some women to think twice about the ‘no-brainer’ decision about whether to get a mammogram or not.
Another cancer that might be, theoretically at least, amenable to screening is ovarian cancer. The results of the first assessment of the effects of ovarian cancer screening are in, and they make for uncomfortable reading.
80,000 took part in the trial, and either underwent active screening or usual care over a 13-year period. Screening involved blood testing for ‘cancer antigen 125’ (CA125) as well as ultrasound via the vagina (transvaginal ultrasound).
At the end of the assessment 212 of the screened women had been diagnosed with ovarian cancer, compared to 176 of those who were not screened.
However, death rates from ovarian cancer (as well as overall risk of death) were the same. In other words, screening for ovarian cancer did not save lives.
It’s important to remember, though, that as a result of screening, a lot of women got investigations and treatment that, in the final analysis, did not help them, and may actually have caused them harm. As a result of screening, more than 3000 women ended up with ‘false-positive’ results (tests indicated the presence of ovarian cancer though there was no cancer present).
Over a thousand of these women had unnecessary surgery as a result, of which about 15 per cent had a serious complication in the form of, say, infection, injury to the bowel and deep vein thrombosis (blood clots in the legs that can break off and go to the lungs causing what is known as ‘pulmonary embolism’ and possible death).
The results of this trial mirror, I think, those which have assessed mammography. It’s another example of something in medicine that keeps the wheels of the medical industry churning away and promises a lot, but in reality delivers very little.