Pet Scans Unreliable?

I was diagnosed with SCC of the right tonsil last November and underwent all my prescribed treatments. When I was first diagnosed I received a PET scan that showed no active cancer. A CT scan revealed that it had actually spread to 4 lymph nodes in my neck. I've had 2 additonal PETs since then and neither of them "lit up". As I talk to more and more cancer survivors and read posts on cancer boards like this one I am struck by how many people have had clean PET scans when they indeed did have cancer. Is this test unreliable? Has anybody else noticed this? As I think now I can't recall hearing from anybody that they've had a PET scan come out positive even though they were diagnosed with cancer. I don't think I have much confidence in PETs as a diagnostic tool.

I originally had colon cancer found during a colonoscopy. Since then I had a Petscan show a tumor in my abdomen in February when my CEA markers were in the mid 50's. Two weeks ago I had the scan show a tumor another tumor in my abdomen and something lighting up in my neck as well. Both suspected to be in the lymphnode system. Catscan after the petscan verified the results on both occassions. The markers the second time were again in the mid 50's. Scan's before my CEA level was in the 50's all showed clean so I'm assuming too small to see. The first time markers went from 2.0 to 55 over a 12 month period so all the scans inbetween showed nothing. this time jumped to 55 two months after surgery. So for what it's worth it did find mine both times. Would be nice if they were more consistant. The waiting sucks. :)

From a RT - x-ray, CT, nuc med, MRI, DEXA, II, portables and PET are my life. And hey, some months it even pays the bills.

If using PET for diagnosis, make sure that you are recieving PET/CT fusion with 4D. These machines came out 5 years ago and are very costly, hence alot of smaller areas will not have them. You also need to make sure the radiologist whom will be reading this exam is up to date and EXPERIENCED in PET/CT.

PET/CT adds sensitivty and specificty in tumor staging and is much MORE accurate than either PET or CT alone. Exam times are shorter - about 30 minutes and PET/CT improves PROPER staging with better treatment planning which in turn improves the chances of cure rates which reduces morbidity.

Simply put, this technology is MUCH better, and is far MORE accurate. The cost to the patient is about the same. This technology is BEST used BEFORE surgery and BEFORE treatment starts.

If your oncologist is suggesting PET. Ask for PET/CT FUSION. If this is unavailable in your area, try to go where it is.

If your doctor has a "limited", "free standing" or "mobile" PET, ask why he feels this is a quality exam for his patients. Most of this equipment is out dated and limited.

Finally, inquire about the tech. Are they registered? Are they in fact NUC MED registered? If not...why? Are they experienced? Keep in mind not every state requires this. One bad tech = one VERY bad exam. Motion artifacts, wrong calculations, and incorrect dosing may equal a wrong diagnosis.

I hope your future in the imaging areas goes smoothly. I pride myself on my work. Been in a level one, 720 bed hospital for 16 years now. I wish you the best with all you must be facing.
Hope this helped.

Radiation Ruth

a PET scan depends on high-metabolism-glucose starved cancer cells to actively uptake the radioactive sugar (FDG) that is injected 45 minutes before the scan.

no matter how good the tech is, no matter how modern the machine, no matter how extensive your cancer is -- if you do not STARVE yourself of carbohydrates the day before the test, the test will be of no value.

outpatient PET facilities often do a good job having the receptionist call and remind patients about the no carbohydrate prep the day before the test, although if the test is on a Monday or if the receptionist is having a busy day she may forget to call.

when an inpatient is scheduled for a PET, very commonly no dietary adjustment is made, nor is the patient even told to avoid sweets, breads, rice, potatoes, regular sodas etc. When a surgeon writes orders for surgery, the surgeon or his resident writes a page of orders which include "NPO p MN" (nothing per ora after midnight = fasting after midnight). When the oncologist writes the order for PET scan, he writes "PET scan" but frequently no dietary modification. When the order is put in the computer, a good system would be for the computer to automatically adjust the patient's diet the day before to eliminate carbohydrates, but I have yet to ever see that done anywhere. This is 2006. Maybe by 2010 this will not be an issue anymore.

So yes, PET scans are only as good as the prep, the tech, and the machine.

I am being scheduled for this test within the next 2 weeks. What diet would you suggest the day before the test - especially someone whose daily intake consists of organic fruits, veggies, nuts, oatmeal, barley, rice soup, lactose free skim milk, yogurt and very little organic meat? Sweets are not an issue, but what foods can a cancer patient eat before the test? Is it similar to a diet prior to a colonoscopy? Thank you for the heads-up on the diet issue. I appreciate your time.

Dear Madeline,

read this and if you have any questions i will be glad to try to answer them!

-Amnia

Link to PET prep including diet:
http://www.csmc.edu/10093.html

Please ask for the results of your PET scan and educate yourself about PET scan...did they do a good job with reading your scan? or performing it?
Who knows.No tests are perfect I had ovarian cancer growing with CA 125 at 28. So as you see there are different scans like MRI. Too much radiation "feeds" the cancer in your body.
Take care, Elunia.

would the pet scan show cancers in areas that the cancer might have spread to. Example-colon to liver...if we ate the wrong food?

 

My dad was diagnosed with oral cancer in the jaw. The jaw bone was removed (resection) and reconstructed using an artificial mandible. No PET scan was performed before the surgery. he is back home after the surgery. Can we perform a PET scan right away or do we need to wait till the wounds from surgery have healed.

I have had 3 pet ct scans, and all 3 showed something.  My first one showed 2 spots in my chest, the 2nd one showed 2 other spots somewhere else, and didn't mention the one in my chest, and the 3rd all spots were mentioned, including under my left arm.  I am now on chemo medication call xeleoda and herceptin and zometa.  My doctor says all they can do is give me pills to keep the pain down if this doesn't work.  I just feel I have done something wrong and don't know what.  I am only 51 years old and have 2 beautiful children to raise.  Good luck with your treatments.