For cancer diagnosis, there is biopsy, an invasive technique. However, PET CT, SPECT CT, MRI are non-invasive. Do oncologists still require the use of biopsy to ascertain type of cancer, i.e., to confirm the presence or absence of malignancy? If so, why?


In many cases yes, a tumor must be biopsied in order to determine exactly what type of tumor it is. Advanced imaging can, in some cases, diagnose a specific type of tumor. However, there are many chemotherapy agents that are very specific not just to a particular tumor, but a particular tumor with certain genetic factors (such as presence or lack of specific receptors), so it is impossible to plan the best treatment without tissue.

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  • We work differently than most SE sites in that we have a strict policy that all answers should be backed up with reliable references so that the answer can be independently verified regardless of the reader's background. See this list of reliable sources. If you still have trouble with this, feel free to visit the help center or Medical Sciences Meta. Unreferenced claims can lead to answers being deleted. – Carey Gregory Jun 13 at 20:44
  • @CareyGregory There is a paucity of free, open-access literature from which to cite for basic topics such as this. It is possible to cite multiple studies that reference a particular genetic marker, but in general those references are too high-level for this specific question. – RudyB Jun 13 at 20:50
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    I think a biopsy is usually ordered after these scans. I had PET then CT then biopsy. Chemo and radiation for the cancer, then two years later the routine CT showed something, got a PET and then it was still necessary for a biopsy ( MDAnderson- presumably they know what is necessary). – blacksmith37 Jun 13 at 20:57
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    @RudyB I understand and what you added is perfectly sufficient. We don't need a doctoral thesis level of citations, just a basic sanity check or two. – Carey Gregory Jun 14 at 4:37
  • @blacksmith37 The order depends upon multiple factors. In my practice, I can literally get a CT performed in minutes if I really need to (usually for strokes and traumas), and some days I can get an MRI done within half an hour (but almost always only for stroke or spinal cord compression). Granted, I have not ever ordered a PET-CT, those may take some time to arrange or require travel. Interventional radiology also may take some time and/ or require travel in order to get a biopsy performed (or general surgery, or pulmonology, etc.). – RudyB Jun 15 at 0:04

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