Hypofractionated image-guided breath-hold SABR (stereotactic ablative body radiotherapy) of liver metastases--clinical results.
OBJECTIVE
Stereotactic Ablative Body Radiotherapy (SABR) is a non-invasive therapy option for inoperable liver oligometastases. Outcome and toxicity were retrospectively evaluated in a single-institution patient cohort who had undergone ultrasound-guided breath-hold SABR.


METHODS
19 patients with liver metastases of various primary tumors consecutively treated with SABR (image-guidance with stereotactic ultrasound in combination with computer-controlled breath-hold) were analysed regarding overall-survival (OS), progression-free-survival (PFS), progression pattern, local control (LC), acute and late toxicity.


RESULTS
PTV (planning target volume)-size was 108 ± 109cm3 (median 67.4 cm3). BED2 (Biologically effective dose in 2 Gy fraction) was 83.3 ± 26.2 Gy (median 78 Gy). Median follow-up and median OS were 12 months. Actuarial 2-year-OS-rate was 31%. Median PFS was 4 months, actuarial 1-year-PFS-rate was 20%. Site of first progression was predominantly distant. Regression of irradiated lesions was observed in 84% (median time to detection of regression was 2 months). Actuarial 6-month-LC-rate was 92%, 1- and 2-years-LC-rate 57%, respectively. BED2 influenced LC. When a cut-off of BED2 = 78 Gy was used, the higher BED2 values resulted in improved local control with a statistical trend to significance (p = 0.0999). Larger PTV-sizes, inversely correlated with applied dose, resulted in lower local control, also with a trend to significance (p-value = 0.08) when a volume cut-off of 67 cm3 was used.No local relapse was observed at PTV-sizes < 67 cm3 and BED2 > 78 Gy. No acute clinical toxicity > °2 was observed. Late toxicity was also ≤ °2 with the exception of one gastrointestinal bleeding-episode 1 year post-SABR. A statistically significant elevation in the acute phase was observed for alkaline-phosphatase; in the chronic phase for alkaline-phosphatase, bilirubine, cholinesterase and C-reactive protein.


CONCLUSIONS
A trend to statistically significant correlation of local progression was observed for BED2 and PTV-size. Dose-levels BED2 > 78 Gy cannot be reached in large lesions constituting a significant fraction of this series. Image-guided SABR (igSABR) is therefore an effective non-invasive treatment modality with low toxicity in patients with small inoperable liver metastases.
Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany. judit.boda-heggemann@umm.de
Judit
J
Boda-Heggemann
Dietmar
D
Dinter
Christel
C
Weiss
Anian
A
Frauenfeld
Kerstin
K
Siebenlist
Ulrike
U
Attenberger
Martine
M
Ottstadt
Frank
F
Schneider
Ralf-Dieter
RD
Hofheinz
Frederik
F
Wenz
Frank
F
Lohr
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D062485:Breath Holding; D002277:Carcinoma / Q000401:mortality / Q000532:radiotherapy* / Q000556:secondary; D015331:Cohort Studies; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000401:mortality / Q000532:radiotherapy* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012189:Retrospective Studies; D016019:Survival Analysis; D016896:Treatment Outcome