PET and PET/CT in gastrointestinal stromal tumours: the unanswered questions and the potential newer applications

Excerpt

The scientific evidence over the last decade has demonstrated the revolutionary impact of FDG PET as an excellent molecular imaging tool for evaluating early therapeutic response of gastrointestinal stromal tumours (GIST) to imatinib mesylate [1]. By now, it is quite evident that the early response of GIST to imatinib therapy cannot be reliably monitored by the World Health Organization (WHO) criteria, Response Evaluation Criteria in Solid Tumors (RECIST) or the Southwest Oncology Group (SWOG) criteria for assessing treatment response that are solely based upon changes in the tumour size measured by morphological imaging modalities. The results have now been well validated in multiple head-to-head prospective studies with sufficient statistical strength [2‐13] that have convincingly proven that FDG PET or PET/CT imaging has been the imaging modality of choice to assess metabolic activity in this group of tumours. Comparing PET activity before and after the start of tyrosine kinase inhibitors provides critical information in identifying active disease and for the assessment of the response to drug treatment. While this has been the major thrust and the frequently highlighted aspect of FDG PET imaging in the management of GISTs, there are other practical issues where this powerful imaging modality can be of great help, and answering these clinical concerns is likely to further enhance the prospects of PET-guided personalized medicine in GIST. …