Re-evaluating the Benefits of Cancer Screening 253
uncleO writes "An article in the NY Times describes two studies that weigh the harm caused by cancer screenings against the benefits they provide. From the article, 'Two recent clinical trials of prostate cancer screening cast doubt on whether many lives — or any — are saved. And it said that screening often leads to what can be disabling treatments for men whose cancer otherwise would never have harmed them. A new analysis of mammography concluded that while mammograms find cancer in 138,000 women each year, as many as 120,000 to 134,000 of those women either have cancers that are already lethal or have cancers that grow so slowly they do not need to be treated. ... In recent years, researchers have found that many, if not most, cancers are indolent. They grow very slowly or stop growing altogether. Some even regress and do not need to be treated — they are harmless."
Blood tests (Score:4, Interesting)
I'm curious why blood tests aren't peformed regularly. You can certainly request Alpha-fetoprotein (AFP) any time you like, but it is not commonly recommended on a regular basis. AFP can indicate tumors growing in the body. Very high levels of AFP can indicate advanced cancer. In the case of a co-worker who was found to have advanced cancer, on first diagnosis, why not have this marker checked every 6 months?
I've been told a normal reading is about 100-120. Values over 10,000 should be investigated. Lance Armstrong, had levels of over 100,000 when he was diagnosed, with tumors spread throughout his body.
It seems a low impact test, why is it not advised as part of a standard checkup? We'll look for chelesterol, why not Alpha-fetoprotein?
Re:indolent (Score:4, Interesting)
I thought that was insolent.
OK, here are the things that can happen in a cancer screening:
1. You find a cancer that will eventually kill you AND that particular cancer has a treatment that works better when started earlier. (True Positive result)
2. You don't find a cancer that you don't have. (True Negative result)
3. You find a cancer or something that looks like a cancer however it will grow so slowly or regress so it won't cause any harm, but then you don't really know which is which so you elect to be treated for same with some morbidity or mortality. (False Positive result)
4. You don't find the cancer that existed and goes off to knock you off just before you design the next iPad killer. (False negative result).
Only #1 and #2 are unequivocally good. #3 might be a bit of a problem - say a lumpectomy for Ductal carcinoma in situ (DCIS) - which is painful and maybe slightly disfiguring but doesn't really change your overall health or it might be a radical prostatectomy for an indolent prostate cancer that would never kill you but now your are incontinent and impotent (a relatively common outcome). #4 is only bad if you would have been helped by earlier detection which is a theory often proposed but often doesn't hold up to scrutiny.
Right now the biggest noise is around breast cancer which unfortunately has problems with all four potential outcomes. You can miss aggressive cancers on mammography. It is not at all clear that getting aggressive cancers early affects any change in outcome. There are many, many false positives. There are a number of breast cancers (DCIS for example) that left alone, typically don't do anything.
So the 'preventative medicine' bandwagon needs to be taken down a notch or two. It is not helped at all that most of the bigger players in cancer research and therapy stand to gain by aggressive detection treatment strategies.
Patients, not so much.
Re:indolent (Score:5, Interesting)
You're leaving out #5:
You find a cancer that is so aggressive that it will kill you no matter what, but you still treat it and the treatment kills you faster or reduces the quality of your remaining life.
Re:Blood tests (Score:4, Interesting)
I'm curious why blood tests aren't peformed regularly. You can certainly request Alpha-fetoprotein (AFP) any time you like, but it is not commonly recommended on a regular basis. AFP can indicate tumors growing in the body. Very high levels of AFP can indicate advanced cancer. In the case of a co-worker who was found to have advanced cancer, on first diagnosis, why not have this marker checked every 6 months?
I've been told a normal reading is about 100-120. Values over 10,000 should be investigated. Lance Armstrong, had levels of over 100,000 when he was diagnosed, with tumors spread throughout his body.
It seems a low impact test, why is it not advised as part of a standard checkup? We'll look for chelesterol, why not Alpha-fetoprotein?
Because, AFP is a crummy screening test [wikimedia.org].
We look for cholesterol because heart disease is one of the major killers of society. Testicular cancer isn't. It is also not terribly sensitive, not very specific and it isn't clear that early treatment helps. You need various qualities of all three aspects for something to be a good screening test.