Volumetric modulated arc therapy for advanced pancreatic cancer.
BACKGROUND
Intensity-modulated radiotherapy (IMRT) allows for improved sparing of organs at risk (OARs) in advanced pancreatic cancer. A planning study evaluated if volumetric modulated arc therapy (RapidArc [RA]) could be used as an alternative to IMRT in such cases.


METHODS
In ten patients, five-field IMRT (5f-IMRT) plans with fixed gantry positions were compared to RA plans using similar constraints for planning target volume (PTV) and OARs. PTV coverage, conformity indices (CI), and OAR doses were compared. One patient was treated using RA and calculated dose distributions were measured in coronal planes in a solid-water phantom.


RESULTS
RA plans showed superior mean CI of 1.09 +/- 0.02 (+/- 1 SD [standard deviation]) versus 1.20 +/- 0.10 in 5f-IMRT (p = 0.003). Both techniques achieved similar sparing of the right kidney, but RA significantly reduced left kidney doses with V(15) of 7.2% +/- 5.3% and 15.9% +/- 11.1%, respectively; p = 0.02. RA modestly decreased mean doses to liver (13.8 vs. 15.1 Gy; p = 0.003), stomach (16.7 vs. 17.9 Gy; p = 0.017), small bowel (19.8 vs. 22.1 Gy; p < 0.001), and duodenum (38.8 vs. 41.9 Gy; p = 0.004). Film dosimetry revealed excellent agreement between calculated and measured dose distributions. The delivery time for RA was < 3 min.


CONCLUSIONS
RA planning achieved superior CI for pancreatic tumors compared to 5f-IMRT, and modestly reduced OAR doses. Fast treatment delivery using RA may decrease the risk of intrafractional organ motion.
Eppinga
Wietse
W
Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands.
Lagerwaard
Frank
F
Verbakel
Wilko
W
Slotman
Ben
B
Senan
Suresh
S
D000465:Algorithms; D000970:Antineoplastic Agents / Q000627:therapeutic use; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D003131:Combined Modality Therapy; D003841:Deoxycytidine / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives; D005373:Film Dosimetry; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007422:Intestines / Q000528:radiation effects; D007668:Kidney / Q000528:radiation effects; D008099:Liver / Q000528:radiation effects; D009367:Neoplasm Staging; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000517:prevention & control; D011836:Radiation Tolerance; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D013116:Spinal Cord / Q000528:radiation effects; D013270:Stomach / Q000528:radiation effects; D014057:Tomography, X-Ray Computed / Q000379:methods; D000093542:Gemcitabine
D000970:Antineoplastic Agents; D003841:Deoxycytidine; D000093542:Gemcitabine