Usefulness of whole body FDG18 PET-CT imaging in comprehensive oncologic management - initial experience

Aims: Retrospective analysis of outcome with PET-CT imaging used for various clinical situations. Materials and Methods: Whole body PET-CT scan of 29 patients was evaluated. In first group, PET-CT was used for response evaluation after curative radio-chemotherapy. In second group, PET-CT was used as an additional diagnostic tool. In third group, PET-CT was used for delineating target volume. For first and second group, uptake was recorded with respect to primary, regional and distant site of involvement and confirmed through PET-CT guided biopsies whenever required. For third group, hypermetabolic volume delineated on PET image was compared with gross target volume delineated on CT image. Results: In first group, 50 % (6/12) of the patients had distant systemic disease, 33% (4/12) had residual regional disease and 58% (7/12) had residual/recurrent local disease. In second group, 30% (3/10) patients had distant systemic disease on PET-CT where CT was inconclusive. 25% (4/10) had variable extent of disease involvement on PET-CT that changed the technique of radiotherapy treatment. In 20% (2/10) patients, PET-CT changed the sequence of treatment. In third group (n=7), PET delineated volume was significantly higher (10-50%) than CT delineated volume for local site but for regional targets the difference was <10%. Conclusions: With the initial use of FDG18 PET-CT imaging, we realized that rate of distant metastasis is much higher which usually remain unnoticed because of conventional approach of investigation. PET-CT imaging has potential to improve the method of conventional IMRT planning.