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.