• Which test is most accurate to detect spread of cancer, CT Scan or PET/CT Scan?

    Asked by queen on Monday, February 18, 2013

    Which test is most accurate to detect spread of cancer, CT Scan or PET/CT Scan?

    Breast cancer spread to lung

    6 Answers from the Community

    6 answers
    • nancyjac's Avatar

      It isn't a matter of which is better, they do different things. A PET measures shows metabolic activity and cancer is one of many things that show a high level of metabolic activity. A CT is used to measure the size of an already identified mass. Since the PET is a whole body scan, then it would be an appropriate preliminary scan if looking for possible metastasis anywhere in the body. If the intent is to identify or measure a tumor in a specific area (such as the lungs), then a CT scan would be more appropriate.

      over 3 years ago
    • carm's Avatar

      A PET will give you a more definitive diagnosis. It targets only one type of cellular activity, rapidly deviding cells that require more glucose for the energy they expend. In other disciplines, it is used to detect lack of activity as in the study of Alzheimers dementia however, in oncology it is used to validate a malignancy. Most radiologists who read CTs will suggest a follow up PET to confirm a suspicion. I have attached a link to help you understand the use of a PET in oncology, Carm RN.

      over 3 years ago
    • nancyjac's Avatar

      Carm, My oncologist explained it to me as being just the opposite. I had several hot spots on my PET which was the first scan I had. (other than a mammogram). All but one of them were not cancer. If my oncologist had assumed that every area which has rapidly dividing cells was malignant, I would have had a much different treatment plan. But most of the hot spots were because of inflammations (e.g. arthritis) or infections (e.g. sinusitis, upper respiratory infection) at the time of the scan. White blood cells, which also rapidly divide in cases of inflammation or infection, not cancer cells, were what were creating the hot spots, not a malignancy. The PET was the preliminary scan. The CT was the follow up scan to determine which PET hot spots were measurable tumors vs normal tissue with a temporarily high white blood count.

      over 3 years ago
    • Joachima's Avatar

      I had a CAT Scan in May 2012 when I finished chemo and was about to start radiation. There was a suspicious spot, so my oncologist ordered a PET Scan to clarify. Thankfully, it was not cancer. My Oncologist explained that my insurance company requires that the CAT Scan be done first. Only if there is a suspicious area, they will approve the PET Scan. Hope this helps.

      over 3 years ago
    • Peroll's Avatar

      Queen, From a technical standpoint (I am an engineer not a Dr) neither the PET or the CT scan are 100% able to determine if cancer has spread as nancjac said the PET sees metabolic activity and the CT sees tissue density differences and cancer is generally more dense and more metabiolicaly active than most "normal" tissue. However as noted there are a number of things that can also be denser or metaboicaly active than "normal" so neither is difinitive to diagnose cancer. Most Drs will state that the PET scan is more definitive of the two because there are fewer things that are active like cancer, but the CT scan can actually see smaller spots (3 to 4 mm vs 6 to 7 mm). CT scans are often used more frequently as they are less expensive and time consuming, but some Drs do things differently.

      You should be aware that about half the population has spots in thier lungs that will show on a CT scan, and sometimnes light up on a PET scan, that are not cancer; however, most Drs will assume that any spot ion the lung of someone that has had cancer is infact cancer. You should ask your Drs if the spots are in a location that can be bipopsied to get a definitnve answer. Some pots are in locations that can not be effectivly biopsied safely and in any biopsey there is the possibility of a false negitive (they just miss the cancer with the biopsy). If it can't be biopsied and is small then just watching the spots to see if they grow like cancer may be a good option is your cancer is not too agressive. Again you need to talk to your Drs about this and get thier advice. Good Luck

      over 3 years ago
    • SueRae1's Avatar

      I have never had a PET scan. I have regular CT of my chest, MRI w/contrast of my abdomen and pelvis (I have lesions on my liver from both my cancers), and Bone Scans. The bone scan is a full body scan, which picks up anomalies.

      over 3 years ago

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