PET/CT in assessing stereotactic body radiotherapy (SBRT) in patients with oligometastatic disease of the lung
- Kostadinova, N. Nedev, G. Mateva, R. Sekalova
The purpose of this retrospective study is to assess the effect of stereotactic body radiotherapy (SBRT) in patients with oligometastatic disease of the lung, using PET/CT and to compare the obtained information from the PET and the CT part of the study. We have reviewed 20 patients with 3 or less lung metastases from different tumours treated with SBRT, of whom- 7 were with breast carcinoma, 6 – with colorectal cancer, 4 – with lung carcinoma, 2 – with renal and 1 with gastric cancer. Prior to and after the radiotherapy (3–6 months after completion of treatment) the effect was evaluated with PET/CT, using both PERCIST and RECIST criteria. The patients were treated on Varian TrueBeam STx™ linear accelerator, the respiratory motion was assessed with 4DCT, The average BED 10 (biologically effective dose 10Gy) was 80.95Gy (range 59,5 – 198,72), delivered in 1 to 5 fractions. The effect of the treatment was evaluated with the change of SUVmax and the sizes of the lesions and the results were compared. According to PET and PERCIST criteria, a local control, defined as lesions with complete response, partial response and stable disease, was achieved in 86%. The average SUVmax was 6,70 before treatment and dropped to 2,97 after the treatment. The decrease was statistically significant (p=0,03) with a strong correlation between the values prior to- and after the SBRT (r=0,76). Using CT and RECIST criteria, there was the same ultimate therapeutic control – 86%, with a change of the average size of lesions – from 15,6 mm to 12,1mm, but the difference was not statistically significant comparing the pretreatment and post treatment sizes (p=0,39) with an average correlation (r=0,60). Therefore the changes in PET-part of the study, using SUVmax, appear earlier and are more pronounced than morphological ones with CT. We did not find any correlation between the delivered dose (BED 10) and the drop in SUVmax or the size of the lesions, as well, after the SBRT. As a conclusion we could say, that SBRT is an effective treatment for patients with oligometastatic lung disease. PET is the more sensitive part of the hybrid imaging method than CT for evaluation of treatment response. There is no correlation between the change of SUVmax and size of the lesion with the delivered dose.
Key words: PET/CT. SBRT. TREATMENT RESPONSE