Detecting cancer early?

[Ultraviolet]

How is cancer detected early? I seem to remember hearing that most cancers don't show symptoms until they are more advanced. Can the standard "yearly physical" bloodtests indicate cancer at all?

[Si Amigo]

I beleive that you can pay out of pocket (say $5-$10K) for things like full body MRI's that can detect things like lung tumors early enough to be operated on. I don't beleive that x-rays alone can spot them when they are small. Once tumors get big enough to show physical symptons it can be too late because they wrap themselves around critical blood vessels.

[KarlGauss]

Cancer can be detected early in a number of ways. More importantly, "precancerous" tumors can be detected before they become cancers.

Examples of early detection and/or detection of precancerous growths include Pap smears, mammography, stool testing for blood, and colonoscopy for bowel polyps.

CT scans of the chest can also detect some early, potentially curable, lung cancers.

One of the traps, though, with screening for early cancers is that, by definition, you're more likely to find the least aggressive cancers this way (i.e. by definition slow growing tumors will be around longer to be detected). Also, for some cancers, there is still not a lot of proof that early detection changes life expectancy, i.e. you just know about the cancer for a longer period.

[KarlGauss]

To clarify:

PAP smears - cervix cancer (and precancers)
mammography - breast cancers
stool for blood - bowel (colon/rectum) cancers (and precancerous polyps)
colonoscopy - bowel (colon/rectum) cancers (and precancerous polyps)

[zagloba]

What about
- monthly home breast exams (palpation)
- being alert to skin cancer signs (changes in warts and moles, etc.)

[Yeah]

American taxpayers pay experts to think about this. You can find the USPSTF cancer screening recs at:

http://www.ahrq.gov/clinic/cps3dix.htm#cancer

Unfortunately, they don't address your question on moles. They do discuss screening for skin cancer (which is not what you asked about):

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* The U.S. Preventive Services Task Force (USPSTF) concludes that the evidence is insufficient to recommend for or against routine screening for skin cancer using a total-body skin examination for the early detection of cutaneous melanoma, basal cell cancer, or squamous cell skin cancer.

Rating: I recommendation.

Rationale: Evidence is lacking that skin examination by clinicians is effective in reducing mortality or morbidity from skin cancer. The USPSTF could not determine the benefits and harms of periodic skin examination. (Go to Clinical Considerations for discussion of selected populations at high risk.)
_______________________________________
They DO address routine BSE:
_______________________________________
# The USPSTF concludes that the evidence is insufficient to recommend for or against teaching or performing routine breast self-examination (BSE).

Rating: I recommendation.

Rationale: The USPSTF found poor evidence to determine whether BSE reduces breast cancer mortality. The USPSTF found fair evidence that BSE is associated with an increased risk for false-positive results and biopsies. Due to design limitations of published and ongoing studies of BSE, the USPSTF could not determine the balance of benefits and potential harms of BSE.
_______________________________________
Keep in mind that a lack of evidence that something works is not proof that it doesn't work.

[Eva Luna]

Originally Posted by KarlGauss

To clarify:

PAP smears - cervix cancer (and precancers)

A routine Pap smear may well have saved my life, or at the very least a large chunk of my reproductive system, 4 years ago. It found cervical cancer which was just on the brink of becoming invasive, just one year after the last of my lifelong, boring, clean Pap smears.

The survival rate for cervical cancer caught before it becomes invasive? Well over 95%, by most stats I've seen. The survival rate for cervical cancer found after it becomes invasive? 7%.

Yes, I'm witnessing here, but at least I'm around to do it. Regular exams are your friend.

[Askance]

Originally Posted by Ultraviolet

How is cancer detected early? I seem to remember hearing that most cancers don't show symptoms until they are more advanced. Can the standard "yearly physical" bloodtests indicate cancer at all?

There is no such disease as cancer - it is a type of disease. This is equivalent to asking "How is infection detected early?". In both cases it completely depends on which one you are referring to.

[gigi]

Originally Posted by KarlGauss

One of the traps, though, with screening for early cancers is that, by definition, you're more likely to find the least aggressive cancers this way (i.e. by definition slow growing tumors will be around longer to be detected). Also, for some cancers, there is still not a lot of proof that early detection changes life expectancy, i.e. you just know about the cancer for a longer period.

At the risk of getting into debate territory, passing on a couple of articles re: screening:
http://www.dartmouth.edu/~news/relea...h/032203j.html
http://dms.dartmouth.edu/news/2005_h...elebrity.shtml
http://www.dartmouth.edu/~vox/0304/0209/cancer.html

from the third article <<"There is growing recognition among medical professionals that cancer screening is a double-edged sword," write the investigators, who include Lisa M. Schwartz and Steven Woloshin, Associate Professors of Medicine, and Gilbert Welch, Professor of Medicine. "While some individuals may benefit from early detection, others may only be diagnosed and treated for cancer unnecessarily. The public needs access to balanced information about [cancer screening's] potential benefits and harms.">>

[Ultraviolet]

Originally Posted by Askance

There is no such disease as cancer - it is a type of disease. This is equivalent to asking "How is infection detected early?". In both cases it completely depends on which one you are referring to.

Well, to clarify, what got me curious was during my last physical, when the clinical nurse said that if I had a severe deficiency of some vitamin ( I forget which ), that it would show up on the standard physical-exam bloodwork. That got me thinking, that if the standard bloodwork can show things like vitamin deficiencies, could it show signs of something like cancer. I admit, I'm not the most medically knowledgeable, but for example : would your body try to combat the cancer, therefore causing raised levels of something that would show up in a normal blood test?

[MLS]

Originally Posted by Ultraviolet

Well, to clarify, what got me curious was during my last physical, when the clinical nurse said that if I had a severe deficiency of some vitamin ( I forget which ), that it would show up on the standard physical-exam bloodwork. That got me thinking, that if the standard bloodwork can show things like vitamin deficiencies, could it show signs of something like cancer. I admit, I'm not the most medically knowledgeable, but for example : would your body try to combat the cancer, therefore causing raised levels of something that would show up in a normal blood test?

IANAD.

There are some such tests, but they are not all that useful in making an individual diagnosis. One example is the CA-125 test. From here:

CA-125 is a protein produced by ovarian cancer cells. It is true that CA-125 protein levels in the blood can be measured as a marker for ovarian cancer, but it is not a conclusive test. It is not used for screening because of its poor accuracy; there are some harmless reasons that CA-125 levels can be elevated. In addition, only about half of the women with an early stage ovarian tumor will have an increased level of CA-125 and only 80% of women with an advanced stage ovarian cancer will have an elevated CA-125 level, according to the American Cancer Society.

The article continues, to say

The best way to identify ovarian cancer is through an abnormality found on a routine pelvic exam. This means the best preventive measure women can take is to have their annual gynecologic exam.

I've read about this test being used in women being treated for ovarian cancer, to look for changes in the CA-125 as a means of seeing if the treatment is working.

There's another test that can be done to look for prostate-specific-antigen (PSA).
More information here. It seems to have similar issues with false positives and false negatives. Lots more info in the link, too much to post here.

It would really be great, though, wouldn't it, if we could get a simple blood test for cancer, like you get a throat swab to check for strep.

[edwino]

Cancer screening and detection is one of the most hotly debated areas in modern medicine. KarlGauss did a wonderful job summing it up in a few sentences. The recommendations go back and forth with each new study to come out. Following the debate is perhaps the toughest job in primary care medicine. The recommendations seem to change monthly.

Simply put, detecting a cancer early doesn't mean you will save lives. The easiest example of this is routine chest X-rays in lung cancer patients. Even though more cancers were detected, no lives were saved. Similar is the new data on prostate cancer, which at its root says that you should think very seriously about treating most prostate cancers that you find.

This is not to state that all tests are useless -- obviously mammogram, Pap smears, routine colorectal screening, and PSA testing have saved thousands. But, even the simple things that we do -- self breast exams for breast cancer, digital rectal exams for prostate cancer and occult blood testing -- are coming under renewed scrutiny. The most validated test for cancer screening, PSA for prostate cancer, is a huge area of debate. Not to mention flex sigs versus colonoscopies, the scheduling of mammograms, the validity of blood cancer markers in screening and following therapy or progression, and the utility of chest CT in detecting lung cancer, as KarlGauss mentioned.

[Yeah]

The various points that Edwino mentions for cancer screening in general are discussed for specific cancer screening tests by the US Preventive Services Task Force at http://www.ahrq.gov/clinic/cps3dix.htm#cancer.

One thing not mentioned is that doctors tend to be much more enthusiastic about screening conducted by members of their specialty than other screening. For example, gynecologists who do Pap smears and see the misery of patients dying from cervical cancer detected too late have recommended more frequent Pap smears than the American Cancer Society whose advisors are not all gynecolotists.

Crunching the numbers (i.e., cost of screening, complications of screening, cost of treatment, complications of treatment, success of treatment, natural history of untreated disease, etc.) only takes you so far in making recommendations. Someone still has to decide, for example, whether it's better to take a chance of a relatively quick death from a perforated colon after a colonoscopy gone awry or to take a chance of slow death from colon cancer.