A prospective study of differences in duodenum compared to remaining small bowel motion between radiation treatments: implications for radiation dose escalation in carcinoma of the pancreas.
OBJECTIVE
As a foundation for a dose escalation trial, we sought to characterize duodenal and non-duodenal small bowel organ motion between fractions of pancreatic radiation therapy.


METHODS
Nine patients (4 women, 5 men) undergoing radiation therapy were enrolled in this prospective study. The patients had up to four weekly CT scans performed during their course of radiation therapy. Pancreas, duodenum and non-duodenal small bowel were then contoured for each CT scan. On the initial scan, a four-field plan was generated to fully cover the pancreas. This plan was registered to each subsequent CT scan. Dose-volume histogram (DVH) analyses were performed for the duodenum, non-duodenal small bowel, large bowel, and pancreas.


RESULTS
With significant individual variation, the volume of duodenum receiving at least 80% of the prescribed dose was consistently greater than the remaining small bowel. In the patient with the largest inter-fraction variation, the fractional volume of non-duodenal small bowel irradiated to at least the 80% isodose line ranged from 1% to 20%. In the patient with the largest inter-fraction variation, the fractional volume of duodenum irradiated to at least the 80% isodose line ranged from 30% to 100%.


CONCLUSIONS
The volume of small bowel irradiated during four-field pancreatic radiation therapy changes substantially between fractions. This suggests dose escalation may be possible. However, dose limits to the duodenum should be stricter than for other segments of small bowel.
Singh
Anurag K
AK
Radiation Oncology Branch, National Cancer Institute, Bethesda, MD 20892, USA. singan@mail.nih.gov
Tierney
Ryan M
RM
Low
Daniel A
DA
Parikh
Parag J
PJ
Myerson
Robert J
RJ
Deasy
Joseph O
JO
Wu
Catherine S
CS
Pereira
Gisele C
GC
Wahab
Sasha H
SH
Mutic
Sasa
S
Grigsby
Perry W
PW
Hope
Andrew J
AJ
D004307:Dose-Response Relationship, Radiation; D004386:Duodenum / Q000528:radiation effects*; D005260:Female; D006801:Humans; D007421:Intestine, Small / Q000528:radiation effects*; D008297:Male; D009038:Motion; D010190:Pancreatic Neoplasms / Q000532:radiotherapy*; D011446:Prospective Studies; D011829:Radiation Dosage; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted