Evidence, not intuition: Why lung cancer screening is not endorsed
It seems intuitive – screening all smokers with a chest CT for earlier detection of lung cancer:
Now, at the time of diagnosis, 75 percent of patients with lung cancer already have symptoms (persistent cough, blood-tinged sputum, chest pain or recurring pneumonia or bronchitis) related to advanced local or metastatic disease that cannot be cured. And by the time a lung tumor is visible on a X-ray, it usually has spread beyond the site where it arose.Only 16 percent of lung cancers are found at a potentially curable stage; the disease is fatal in more than 90 percent of cases over all. But when tumors are found through CT scans in people without symptoms, 80 percent of the cancers are still confined to their original site and potentially curable with surgery alone.
Survival chances are directly related to the stage the cancer has reached when it is detected and treated. For Stage 1 lung cancer, the category of both of Mrs. Guettel’s cancers, five-year survival rates are 50 to 90 percent; for Stage 4, one that has spread to other parts of the body, it is a mere 2 percent.
Alas, guidelines are based on evidence, not intuition. If intuition influenced practice guidelines and recommendations, we’d still believe the earth was flat. The NY Times nicely summarizes the USPSTF’s position:
The main concern is that no study has yet proved that detecting early lung cancers with CT scans improves long-term survival. While one might guess that finding cancers early can produce a permanent cure, this has not yet been demonstrated for lung cancer found through screening. It could be that people’s cancers are found years earlier than they might have been, but they end up dying at the same time they would have if they not been screened.Another possibility is that screening could result in overdiagnosis – finding tiny indolent tumors that would never have threatened life before the patient died of something else.
Want to reduce your risk of lung cancer? Stop smoking.
Related posts:
- How does cancer screening cause harm?
- More tests is better medicine: Why the myth is hard to break
- Should tobacco companies pay for smokers’ CT scans to screen for lung cancer?
- "The distinction between survival and mortality cuts to the heart of the screening debate"
- Lung cancer CT screening produces false positives and isn’t ready for prime time
- Motives behind CT screening
- Should we start screening women for ovarian cancer?
{ 8 comments }
Tell that to the folks who’ve already quit or who never smoked, but had to be around smokers.
Nobody thinks that spiral CT will reduce his or her chance of lung cancer. They think it might increase the chances any lung cancer contracted will be found at an earlier stage of progression, when the cancer is still small and occult and potentially more treatable and survivable.
Precisely my point. As of today, earlier detection –> earlier treatment –> does not equal lives saved.
It is intuitive that that should be the case, but the evidence is not there.
Kevin
Kevin, any comment on the new study regarding the combination of surgery with chemo for higher lung cancer survival rates? How long before the USPTF reviews this information to determine if any change is appropriate?
http://www.medicinenet.com/script/main/art.asp?articlekey=47717
The fact that the USPTF says screening doesn’t help won’t prevent lawyers from suing doctors of patients who get incurable lung cancer due to the “malpractice” of the doctor in failing to order the screening spiral CT.
“the evidence is not there”
But that takes time, and people aren’t a herd of cows.
They are individuals who have an interest in getting a best-case -scenario for themselves.
Screening undoubtedly will help dectect cancer earlier. That alone is a benefit to patients for a multitude of reasons, including wise planning, making the most of good days ahead, setting priorities.
Even if folks who find early cancer through screening won’t get any extra time (which is doubtful, they probably will get extra time, especially as experience in the treatment of early cancer becomes more common).
The only significant downside is the “incidentaloma” issue – but patients can make an informed choice.
While this particular screening test doesn’t apply to me – I am not a smoker and am not around smokers – this issue applies to many screening tests even those that are recommended. As I understand – and I am a patient not a physician, although having a math degree I have above average knowledge of statistics – is that all tests can cause harm as well as benefit. The most serious of the former (and less advertised) is overdiagnosis and overtreatment which, in case of cancer, is something one wants to avoid. So what bugs me is not that patients demand tests – let those who want them have them; but that doctors recommend screening tests universally without ever mentioning that the benefit is uncertain and there is a probability of harm. Just last weekend on Fox Sunday Housecall, Dr Rosenfield recommended spiral CT for smokers. No mention of lack of benefit, no mention of possible harms. In fact, when it comes to screening test, the harms are never mentioned at all. Moreover, very often we are scared into having tests we wouldn’t want if we were given all the facts.
Pap smear is currently recommended every 3 years (after 3 consequitive negative scans) yet most ObGyns keep doing them every year even for women whose lack of sex life puts them at very low risk.
Experts still argue about whether benefits of mammograms especially for women in their 40s are greater than risks, but if I, after carefully reading analysis of the available studies, articles (in medical journals such as BMJ and websites like NCI) on the subject, decide that I don’t want them (because for me 1 in 1700 chance after 10 mammograms that it’ll save my life based on optimistic view of the studies – interestingly though that the study that showed no benefit is both more recent and most reviewed – is not worth for me the 50% chance of false positive, 18% chance of a biopsy and a tangible probability of being treated for something that would’ve never threatened my life), I’d be called irresponsible and harassed and scared by misleading statistics (using relative risk instead of absolute risk as well as hypothetical life-time risk instead of 10-year risk)and pressured.
I think we’ve been lead to believe that early detection is always beneficial, that every second counts, and that there are no harms associated with screening. Media is mostly to blame, but doctors share the blame as well. Had we, the public, been given the fuller picture right away, maybe the perception would’ve been different.
Bravo! You make the points much clearer than I could. Too bad it takes a math degree to do it. I teach stats to medical students and residents, and consequently, to patients, but these issues seldom get across.
One reason for the knee-jerk testing of many physicians is defensive medicine. Even when such a dissertation about the risks of screening does occur, the patient cannot be held responsible for their decision, the physician (or training program, as in the case of the PSA that has been discussed in this blog) is held responsible for not making the recommendation, because the public perception is that there is no harm in testing.
I use the CA-125 example often. This one circulates on the internet every 2 years or so, that women should have screening CA-125 to detect ovarian cancer early. Of course the example case is someone with advanced disease, but that technicality is lost on the reader. Invariably, droves of women come in asking for a CA-125 test to detect ovarian cancer, because no other test will do it. It’s a poor test. Assume that it is done on an otherwise healthy person and is high (”positive”) – what now? Imaging studies are likely to be negative (that is the rationale for doing CA-125 – “it detects before imaging can”) – so what next? Exploratory laparoscopy/laparotomy – for a test that is insensitive and unspecific. Here is one citation:
Moss, EL, el al. The role of CA125 in clinical practice. J Clin Pathol. 2005 Mar;58(3):308-12.
which abstract concludes:
These results confirm the high false positive rate and poor sensitivity and specificity associated with CA125. The substantial inappropriate usage of CA125 has led to results that are useless to the clinician, have cost implications, and add to patient anxiety and clinical uncertainty.
Wait – it will come around again. Snopes.com has a story on the letter that circulates: http://www.snopes.com/toxins/ca125.htm
Tell me if I have this wrong/right: lung cancer is not very curable if discovered late. it is more likely curable if discovered early. Studies show that screening for lung cancer via eg spiral CT doesn’t save lives because, as a group, the people whose lung cancer is caught early by the testing end up dying from something other than lung cancer, so that longevity is not increased by screening tests. Is that correct?
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