Oesophageal tumour progression between the diagnostic ¹⁸F-FDG-PET and the ¹⁸F-FDG-PET for radiotherapy treatment planning.

Abstract

To test whether the interval between diagnostic and therapeutic FDG-PET-scanning is associated with early tumour progression. All patients (n=45) underwent two PET scans, one for staging ('baseline PET') using an HR+ positron camera or PET/CT-scanner and one for radiotherapy planning ('therapeutic PET') using a PET/CT-scanner. All images were reviewed in random order by an experienced nuclear physician. If there were any discrepancies, the images were also compared directly. SUVmax, tumour length, lymph node metastases and distant metastases were assessed. The median time between the PET scans was 22 days (range: 8-49). The SUVmax increased (>10%) (19 patients, 42%) or decreased (11 patients, 24%). Fourteen patients (31%) showed tumour length progression (>1cm). TNM progression was found in 12 patients (27%), with newly detected mediastinal nodes (N) in eight patients (18%) and newly detected distant metastases (M) in six patients (13%). No significant prognostic factors were found. However, a trend was noted towards TNM progression for the type of PET-camera (p=0.05, 95% CI 0.01-0.66) and for the interval between the PET scans (p=0.09, 95% CI -0.9 to 12.5). This study suggests rapid oesophageal tumour progression. Therefore, the interval between relevant imaging and start of the radiotherapy should be minimized. Furthermore, 'state of the art' PET scanners should be used.