Despistaje o no despistaje?

To screen or not to screen

Jun 10th 2011, 12:49 by C.H. | NEW YORK

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CANCER treatments are going from strength to strength. Screening for tumours, by contrast, seems to have hit a rough patch, at least in America. The government has, so far, been reluctant to endorse routine cancer screening. Some established tests, too, have become contentious of late—witness the recent uproar over guidelines for mammograms, or the fight over prostate cancer screening. There is, in other words, a serious question about whether screening does more harm than good.

The Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, led by Saundra Buys of the Huntsman Cancer Institute at the University of Utah, therefore set out to see whether screening is all it is hyped up to be by its armies of relentless proponents (including a fair few celebrities; this is America, after all). In a study reported in the Journal of the American Medical Association (JAMA), Dr Buys and her colleagues reported on the ovarian arm of the project.

Ovarian cancer looks like a good candidate for screening as symptoms often do not appear until it is too advanced to treat. Dr Buys and her colleagues followed over 78,000 women between the ages of 55 and 74 who had no family history of ovarian cancer, for an average of 12 months. As is standard practice in such trials, the women were split at random into two groups. All followed a typical schedule of regular check-ups, but the women in one group were also tested for CA-125, a protein that is sometimes more prevalent in those with ovarian cancer, and were given transvaginal ultrasonic scans designed to detect abnormal signs, such as cysts larger than ten cubic centimetres. For participants in this second group, doctors advised further treatment based on the results of these tests.

What the researchers found was discouraging. The diagnoses were similar for both groups—78% of those cases of ovarian cancer detected in the former were already advanced, as were 77% of those in the latter. However, about one in ten of the women who were given extra screening got false-positive results. They were, in other words, told they had tumours when they did not. One-third of these women went on to have surgery, and 15% of them suffered serious complications. The upshot was that 118 of the screened group died, compared with 100 in the group given only regular check-ups.

The findings thus suggest that, at least for women with an average risk of developing ovarian cancer, screening does not reduce cancer-related mortality. In fact, it may increase it by increasing the number of invasive medical procedures carried out. If Dr Buys is right, then, screening for cancer, at least of the ovaries, may do more harm than good.