The potential advantages of (18)FDG PET/CT-based target volume delineation in radiotherapy planning of head and neck cancer.

PURPOSE: This study investigated two fixed threshold methods to delineate the target volume using (18)FDG PET/CT before and during a course of radical radiotherapy in locally advanced squamous cell carcinoma of the head and neck. MATERIALS AND METHODS: Patients were enrolled into the study between March 2006 and May 2008. (18)FDG PET/CT scans were carried out 72h prior to the start of radiotherapy and then at 10, 44 and 66Gy. Functional volumes were delineated according to the SUV Cut Off (SUVCO) (2.5, 3.0, 3.5, and 4.0bwg/ml) and percentage of the SUVmax (30%, 35%, 40%, 45%, and 50%) thresholds. The background (18)FDG uptake and the SUVmax within the volumes were also assessed. RESULTS: Primary and lymph node volumes for the eight patients significantly reduced with each increase in the delineation threshold (for example 2.5-3.0bwg/ml SUVCO) compared to the baseline threshold at each imaging point. There was a significant reduction in the volume (p⩽0.0001-0.01) after 36Gy compared to the 0Gy by the SUVCO method. There was a negative correlation between the SUVmax within the primary and lymph node volumes and delivered radiation dose (p⩽0.0001-0.011) but no difference in the SUV within the background reference region. The volumes delineated by the PTSUVmax method increased with the increase in the delivered radiation dose after 36Gy because the SUVmax within the region of interest used to define the edge of the volume was equal or less than the background (18)FDG uptake and the software was unable to effectively differentiate between tumour and background uptake. CONCLUSIONS: The changes in the target volumes delineated by the SUVCO method were less susceptible to background (18)FDG uptake compared to those delineated by the PTSUVmax and may be more helpful in radiotherapy planning. The best method and threshold have still to be determined within institutions, both nationally and internationally.

Tumor antivascular effects of radiotherapy combined with combretastatin a4 phosphate in human non-small-cell lung cancer.

PURPOSE: The tumor vascular effects of radiotherapy and subsequent administration of the vascular disrupting agent combretastatin A4 phosphate (CA4P) were studied in patients with advanced non-small-cell lung cancer using volumetric dynamic contrast-enhanced computed tomography (CT). PATIENTS AND METHODS: Following ethical committee approval and informed consent, 8 patients receiving palliative radiotherapy (27 Gy in six fractions, twice weekly) also received CA4P (50 mg/m(2)) after the second fraction of radiotherapy. Changes in dynamic CT parameters of tumor blood volume (BV) and permeability surface area product (PS) were measured for the whole tumor volume, tumor rim, and center after radiotherapy alone and after radiotherapy in combination with CA4P. RESULTS: After the second fraction of radiotherapy, 6 of the 8 patients showed increases in tumor PS (23.6%, p = 0.011). Four hours after CA4P, a reduction in tumor BV (22.9%, p < 0.001) was demonstrated in the same 6 patients. Increase in PS after radiotherapy correlated with reduction in BV after CA4P (r = 0.77, p = 0.026). At 72 h after CA4P, there was a sustained reduction in tumor BV of 29.4% (p < 0.001). Both increase in PS after radiotherapy and reduction in BV after CA4P were greater at the rim of the tumor. The BV reduction at the rim was sustained to 72 h (51.4%, p = 0.014). CONCLUSION: Radiotherapy enhances the tumor antivascular activity of CA4P in human non-small-cell lung cancer, resulting in sustained tumor vascular shutdown.