Dosimetric feasibility of hypofractionated proton radiotherapy for neoadjuvant pancreatic cancer treatment.
OBJECTIVE
To evaluate tumor and normal tissue dosimetry of a 5 cobalt gray equivalent (CGE) x 5 fraction proton radiotherapy schedule, before initiating a clinical trial of neoadjuvant, short-course proton radiotherapy for pancreatic adenocarcinoma.


METHODS
The first 9 pancreatic cancer patients treated with neoadjuvant intensity-modulated radiotherapy (1.8 Gy x 28) at the Massachusetts General Hospital had treatment plans generated using a 5 CGE x 5 fraction proton regimen. To facilitate dosimetric comparisons, clinical target volumes and normal tissue volumes were held constant. Plans were optimized for target volume coverage and normal tissue sparing.


RESULTS
Hypofractionated proton and conventionally fractionated intensity-modulated radiotherapy plans both provided acceptable target volume coverage and dose homogeneity. Improved dose conformality provided by the hypofractionated proton regimen resulted in significant sparing of kidneys, liver, and small bowel, evidenced by significant reductions in the mean doses, expressed as percentage prescribed dose, to these structures. Kidney and liver sparing was most evident in low-dose regions (< or =20% prescribed dose for both kidneys and < or =60% prescribed dose for liver). Improvements in small-bowel dosimetry were observed in high- and low-dose regions. Mean stomach and duodenum doses, expressed as percentage prescribed dose, were similar for the two techniques.


CONCLUSIONS
A proton radiotherapy schedule consisting of 5 fractions of 5 CGE as part of neoadjuvant therapy for adenocarcinoma of the pancreas seems dosimetrically feasible, providing excellent target volume coverage, dose homogeneity, and normal tissue sparing. Hypofractionated proton radiotherapy in this setting merits Phase I clinical trial investigation.
Kozak
Kevin R
KR
Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA.
Kachnic
Lisa A
LA
Adams
Judith
J
Crowley
Elizabeth M
EM
Alexander
Brian M
BM
Mamon
Harvey J
HJ
Fernandez-Del Castillo
Carlos
C
Ryan
David P
DP
DeLaney
Thomas F
TF
Hong
Theodore S
TS
D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy*; D000368:Aged; D019583:Dose Fractionation, Radiation; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007421:Intestine, Small / Q000528:radiation effects; D007668:Kidney / Q000528:radiation effects; D008099:Liver / Q000528:radiation effects; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy*; D061766:Proton Therapy; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013270:Stomach / Q000528:radiation effects; D047368:Tumor Burden; D011522:Protons
D011522:Protons