The value of PET, CT and in-line PET/CT in patients with gastrointestinal stromal tumours: long-term outcome of treatment with imatinib mesylate

Purpose

Gastrointestinal stromal tumours (GIST) are mesenchymal neoplasms of the gastrointestinal tract that are unresponsive to standard sarcoma chemotherapy. Imaging of GIST patients is done with structural and functional methods such as contrast-enhanced helical computed tomography (ceCT) and positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (FDG). The aim of this study was to compare the prognostic power of PET and ceCT and to evaluate the clinical role of PET/CT imaging.

Methods

All patients with GIST undergoing PET or PET/CT examinations were prospectively included in this study, and the median overall survival, time to progression and treatment duration were documented. The prognostic significance of PET and ceCT criteria of treatment response was assessed and PET/CT was compared with PET and ceCT imaging. Data for 34 patients (19 male, 15 female, 21–76 years) undergoing PET or PET/CT for staging or restaging were analysed.

Results

In 28 patients, PET/CT and ceCT were available after introduction of treatment with the tyrosine kinase inhibitor imatinib mesylate (Gleevec; Novartis, Basel, Switzerland). Patients without FDG uptake after the start of treatment had a better prognosis than patients with residual activity. In contrast, ceCT criteria provided insufficient prognostic power. However, more lesions were found on ceCT images than on PET images, and FDG uptake was sometimes very variable. PET/CT delineated active lesions better than did the combination of PET and ceCT imaging.

Conclusion

Both PET and PET/CT provide important prognostic information and have an impact on clinical decision-making in GIST patients. PET/CT precisely delineates lesions and thus allows for the correct planning of surgical interventions.

[The impact of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) on planning of radiotherapy]

AIM

To determine the impact of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) on patient management in radiotherapy.

MATERIAL AND METHODS

One hundred sixty-nine consecutive patients with different malignant tumors were analyzed. Whole-body FDG-PET was performed for staging before radiotherapy. The strategy of radiotherapy before and after PET scanning was compared and the change in the treatment management determined.

RESULTS

In 47(28%) of 169 patients PET results changed patient management in radiotherapy. In 19 patients (11%) radiotherapy was not performed after PET. In 16 patients (10%) PET results changed the intention of radiation treatment (curative/palliative). Correction of radiation dose was made in 16 patients (10%). Correction of the volume of the exposure area was made in 12 patients (7%). Tumor outside the field of view was missed in only 2 patients with a regional PET scan.

CONCLUSION

In this retrospective analysis the information provided by FDG-PET contributes to a substantial change in radiotherapy strategy.

PET-CT-guided percutaneous puncture of an infected cyst in autosomal dominant polycystic kidney disease: case report

An infected cyst in autosomal dominant polycystic kidney disease was identified with a combined positron emission tomographic (PET) and computed tomographic (CT) system, an experimental setup mimicking an integrated CT-PET scanner. Image fusion of fluorine 18 fluorodeoxyglucose PET and CT images allowed exact localization of the infected cyst among many cysts identified on previous CT and magnetic resonance images. Confirmation was obtained instantly, followed by CT-guided percutaneous puncture. Integrated imaging systems hold promise for direct PET-guided puncture of areas of increased fluorodeoxyglucose uptake by using the anatomic accuracy of CT.