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Old 08-14-2006, 04:47 PM   #1
Sherryg683
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PET SCAN..58% False Positive Rate

Just wanted to post this study...pretty interesting. How many of us with mets were diagnosed with a PET scan..I know I was. Got me thinking now if my 2 small lung mets could have been false positives...they were gone by the next scan 6 weeks later...here's hoping anyway.. If my PET lights up again, I am going to insist in more scans or a biopsy..sherryg683

http://www.breastcancer.org/research_screening_071906.html

Whole-Body PET Scans Have High False Positive Rates for Breast Cancer
C.E. Carr and others

American Society of Clinical Oncology Annual Meeting, June 2006, Abstract 530

Is this for me? If you're interested in learning about imaging methods to detect metastatic (advanced) breast cancer in other areas of the body besides the breast and nearby lymph nodes, you might want to read this article.

What questions is the study trying to answer? The researchers wanted to know if PET (positron emission tomography) scans would accurately detect breast cancer that has spread (metastasized) to other areas of the body besides the breast and surrounding lymph nodes. They also wanted to know if PET scans provided information over and above what is learned from mammography, digital mammography, ultrasound, and MRI (magnetic resonance imaging).

If you have a PET scan, you're injected with a small amount of radioactive material. Active cells, which often indicate rapid cancer growth, take up the radioactive material. This helps radiologists identify areas where cells are suspiciously active, which can indicate cancer.

Right now, PET scans are not routinely done on women with breast cancer. Early results of research have shown that PET scanning for women with breast cancer may be help doctors assess whether a cancer still exists after radiation or chemotherapy or whether a cancer has spread to the lymph nodes.

But PET scans have some drawbacks. They have only a limited ability to detect very small cancers. They are not widely available outside major cities. And they are expensive—about $5,000 per scan. It is rare that insurance providers will cover a PET scan for breast cancer.

Study design: The researchers from the Hospital of the University of Pennsylvania looked at 189 women who had been diagnosed with breast cancer (including ductal carcinoma in situ) through biopsy. The women were ages 28 to 81. The women had film mammography, ultrasound, digital mammography, MRI, and whole-body PET scans.

Study results: PET scans identified 59 suspicious sites in 33 of the women. Of these suspicious sites, 50 were considered very likely to be cancer based on results the researchers found after looking at the sites again using CT (computerized tomography) scans, MRI, X-ray, bone scans, or pathology. Biopsy results were not available in all women to confirm the cancer. So the researchers used the results of the imaging screenings (highly suspicious for spread of cancer, or not) to determine whether disease was present or absent.

For these 50 very suspicious sites, the additional tests showed that:

19 were considered likely to be cancer, so they are probably "true positives." In 2 women, the only initial screening test that identified the cancer was the PET scan. That would count as a "true positive" for PET and a "false negative" for the other forms of imaging.


2 were "true positives" and most likely to be non-cancerous tissue.


29 were considered "not cancer" and likely to be "false positives."


The researchers estimated that PET scans could most accurately detect cancer 40% of the time. The false positive rate was 58%.

In addition, MRI — but not the PET scan — revealed signs of cancer in two women. This would count as a "false negative" for the PET scan and a "true positive" for MRI.

Take-home message: This study shows that whole-body PET scans appear to have a relatively high rate of false positives — they tend to show something that looks like cancer but really isn't. These "false alarms" come with a cost beyond the financial cost of the procedure: inconvenience and emotional stress.

For women with metastatic disease, the role of regular imaging is controversial, because early detection of metastases doesn't lead to longer survival. Studies are most commonly done when any signs or symptoms develop. That's what professional associations like the American Society of Clinical Oncology recommend.

Still, you may get regular testing because you don't feel the recommendation applies to your case. Perhaps your doctor says you're at high risk for recurrence, or maybe you feel very strongly that early detection might be helpful to you. Or you may have already been treated for metastatic disease, and now you're being watched carefully in case other areas of disease become a problem. You may have other reasons, not listed here, to want to have regular testing.

Studies like this one, which look at the accuracy of imaging tests, are very important. This study gives us more information to go on when looking for metastases. The different tests have different strengths and weaknesses. Also, some studies show the same kinds of things as other tests, and other studies offer unique value that the other ones don't. But this study showed that PET scans didn't add much benefit beyond the standard tests used to find and evaluate possible areas of breast cancer spread:

MRI


CT


Bone scan


X-ray


Also, PET scans are expensive and are only available in some diagnostic centers. They are also very sophisticated tests and must be done by someone with a lot of experience and training.

Until PET scans can be refined so there are fewer false positives, they probably won't be used routinely to detect the spread of breast cancer. However, PET scanning can be a valuable tool to assess how a cancer is responding to treatment. And, for any particular woman, PET scanning may be able to clarify findings that may be unclear on other tests.

Is 'nt this really shocking??????
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Old 08-14-2006, 06:37 PM   #2
mamacze
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Hi Sherry,
Thank you for posting this study; it is no surprise to me...I had a PET, CAT of lung and abdomen, bone scan and MRI ... only the CAT showed the mets that I had to all 4 lobes of my lungs...my entire PET was negative...it just goes to show that our docs are right on when they order more than one type of test when they are on the hunt for mets...
Love Kim from CT
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Old 08-15-2006, 01:30 PM   #3
Cathya
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Iknow when my onc found the tumor in my clavicular node he insisted on a biopsy even though it was inoperable. I think this was not only to confirm but to assure treatments in the future would be available to me. I wonder if catscans and pet scans are considered confirmation everywhere?

Cathy
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Diagnosed Oct. 2004 3 cm ductal, lumpectomy Nov. 2004
Diagnosed Jan. 2005 tumor in supraclavicular node
Stage ?, Grade 3, ER/PR+, Her2++
4 AC, 4 Taxol, Radiation, Arimidex, Actonel
Herceptin for 9 months until Muga dropped and heart enlarged
Restarting herceptin weekly after 4 months off
Stopped herceptin after four weekly treatments....score dropped to 41
Finished 6 years Arimidex
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