VOLUMETRIC MODULATED ARC THERAPY IN STEREOTACTIC BODY RADIATION THERAPY FOR METASTASES TO ABDOMINAL LYMPH-NO) DES

Fourteen patients were included in the study. Dose prescription was set to 45 Gy (mean dose to CTV) in 6 fractions of 7.5 Gy. Objectives for CTV and PTV were: Dosemin>95%, Dosemax<107%. For organs at risk the following objectives were used: Maximum dose to spine <18Gy; V15Gy<35% for both kidneys, V36Gy<1% for duodenum, V36Gy<3% for stomach and small bowel, V15Gy<(total liver volume - 700 cm3) for liver. DVH were evaluated to assess plan quality. Results Planning objectives on CTV and PTV were achieved by all techniques. RA improved PTV coverage (V95%=90.2±5.2% for RA compared to 82.5±9.6% and 84.5±8.2% for CRT and IM respectively). Most planning objectives for OARs were met by all techniques, except for duodenum, small bowel and stomach where in some patients the CRT plans exceeded the dose/volume constraints. MU/fraction were: 2186±211 for RA, 2583±699 for IM and 1554±153 for CRT.