Tuesday, November 17, 2009

To Screen Or Not To Screen

The new mammogram recommendations have caused a lot of arguments. This is not unexpected at all, because the earlier recommendations sure did sell mammograms as the way to beat breast cancer, and now we are all supposed to do a 180 degrees turn! But the truth is that a mammogram is a form of screening, given to a large number of women, with the intention of finding early cases of breast cancer and with the assumption that such early cases would lend themselves better to the current types of treatment. Those still consist of cutting, poisoning and radiating, by the way. It's important not to forget that our abilities to treat cancers of all types really are pretty medieval.

Screening is not treatment. To do it at all is based on the hope that early detection raises the odds of survival. This has been shown to be true for cervical cancer and the pap test and also for colon cancer screenings. But the most recent evidence suggests that breast cancer screening is less effective than previously thought. As I mentioned in an earlier post, researchers now suspect that mammograms capture a lot of tumors which might either disappear on their own or never grow much, while missing the very aggressive tumors which develop very rapidly. It is the latter types which are reflected in the mortality statistics:

A recent study in the Journal of the American Medical Association (JAMA) pointed out the evidence for this. Breast cancer statistics for women in the Unites States has not shown a reduction of advanced breast cancers being diagnosed, despite the widespread use of mammography.

One would expect that if mammograms diagnosed breast cancers earlier and women were then treated for these cancers, over time there would be a reduction in the diagnosis of more advanced cancers from the "successful" screening. But this is not the case. Advanced cancers continue to be diagnosed with greater than expected frequency.

What makes discussing mammograms so very tricky is that the topic of screening can be approached from two very different points of view.

One of those is the way a survivor of breast cancer would approach it. She had a mammogram, a tumor was found and treated, and she is alive. To then learn that other women are told not to get the mammogram sounds blasphemous to her. Horrible, even. At the same time, perhaps her cancer wasn't the type which progresses very rapidly? Perhaps it wasn't the early screening that saved her life? Or perhaps it did. We just don't know at this stage, because we don't have the ability to look at a tumor and classify it based on how dangerous it is. That is the research that should be carried out now, by the way.

The other angle is to approach mammograms from the point of view of screening large population groups in order to find cases of some disease. When statisticians analyze screening proposals they want to know how many cases can be found if a certain number of people are screened. Remember that screening costs money, both for the health care system and for the people who have to travel and spend time in order to be screened. Even if screening does find cases of a disease it might not be worth doing. To give you an extreme example, suppose that we could save one life by having every American screened for some rare disease. Should we do this? How much money are we willing to spend to potentially save that one life? Then remember that there are many, many other diseases which are rare but which could be screened for in the same manner. If we decided to carry out all possible types of screening the costs would be astronomical.

The choice to pay for screening (by both individuals and the society) is ultimately a value judgment. But resources are not infinite. If money is spent (by both individuals and the society) in one type of screening, it is not available for other types of screening or for other types of prevention or treatment. These are the reasons why something like mammograms deserve careful scrutiny:

Dr. Diana Petitti, vice chairwoman of the task force and a professor of biomedical informatics at Arizona State University, said the guidelines were based on new data and analyses and were aimed at reducing the potential harm from overscreening.

While many women do not think a screening test can be harmful, medical experts say the risks are real. A test can trigger unnecessary further tests, like biopsies, that can create extreme anxiety. And mammograms can find cancers that grow so slowly that they never would be noticed in a woman's lifetime, resulting in unnecessary treatment.

Over all, the report says, the modest benefit of mammograms — reducing the breast cancer death rate by 15 percent — must be weighed against the harms. And those harms loom larger for women in their 40s, who are 60 percent more likely to experience them than women 50 and older but are less likely to have breast cancer, skewing the risk-benefit equation. The task force concluded that one cancer death is prevented for every 1,904 women age 40 to 49 who are screened for 10 years, compared with one death for every 1,339 women age 50 to 74, and one death for every 377 women age 60 to 69.

These figures don't tell us whether mammograms should be recommended for various age groups or not. What they do tell us is that we are saving more lives by screening older women, or, in reverse, each saved life costs less in that age group. If our measure of outcome was years-of-life saved the arguments might change.

The reason for the heated debates has to do with the clashing of these two approaches. The recommendations are based on the second approach (the system-wide, dry and statistical) and the reactions largely on the first approach (the voices of individual women). Note also that the new recommendations leave no active role for women themselves, until the magical age of fifty. Even breast self-examinations are no longer recommended! It's as if you are to sit and wait for the day when you might find a lump in your breast. This is very bad psychology, if nothing else.

Add to that the fairly sudden turn-around in the whole policy, and it's no wonder that many women ask if this is just another way to cut back on health care costs at the eve of the reforms (though it's good to remember that the treatment of well women is a big business in general (remember hormone replacement therapy) and that the screening industry certainly wants to go on existing).

It must be clear to you by now that I'm not going to answer that question in the title of this post, except for all that helpful academese above. But ultimately I want effective treatment, not discussions about how to get people burned, slashed and radiated earlier.