Abstract
1407
Objectives: The gastrointestinal stromal tumor, GIST, tumours are generally effectively treated surgically however, depending on their variable risk, postoperative recurrence rate and disease progression poste chemotherapy with imatinib may occur requiring a change in management in these patients. We evaluated the role of 18F-FDG PET/CT, i.e.PET/CT, in the evaluating treatment response of GIST tumours post therapy adjustment in patients with recurrence or disease progression. MATERIALS AND
Methods: PET/CT scans were done according to departmental protocol following surgery or chemotherapeutic intervention. Disease recurrence, residual disease or progression was confirmed on histology, dedicated imaging or follow up following initial management. Follow up PET/CT was donepost intervention in these patients to evaluate the effectiveness of the change in management by increasing dose of imatinib of surgical excision. RESULTS: 46 patients aged 25 to 84 years, mean = 56.5 ±12.9, with histologically confirmed GIST tumours: 27 stomach, 7 small bowel, 4 mesentery, 3 rectum, 2 gastro-oesophageal junction, 1 oesophagus, 1 bladder and 1 unknown, underwent a total of 161 PET/CT scans ranging from a period of 3 to 18 month intervals depending of the patients risk assessment. A total of 42 scans demonstrated FDG avid disease with 71% were due to recurrence or residual disease, 23% due to disease progression during the surveillance period. Surgical intervention, imatinib increase or commencement, supplemented chemotherapeutic regimen or radiotherapy was instituted post 25 scans demonstrating recurrence or disease progression. Follow up PET/CT post treatment augmentation demonstrated disease improvement, progression and stable disease in 16%, 28% and 32% respectively. CONCLUSION: This study demonstrates the potential role of 18F-FDG PET/CT scan as a valid consideration in the treatment response evaluation post treatment adjustment in recurrence and/or progression of GIST and may assist in early institution of new management or augmentation of ongoing treatment in this setting.