A four-dimensional CT-based evaluation of techniques for gastric irradiation.
OBJECTIVE
To evaluate three-dimensional conformal (3D-CRT), intensity-modulated (IMRT) and respiration-gated radiotherapy (RGRT) techniques for gastric irradiation for target coverage and minimization of renal doses. All techniques were four-dimensional (4D)-CT based, incorporating the intrafractional mobility of the target volume and organs at risk (OAR).


METHODS
The stomach, duodenal C-loop, and OAR (kidneys, liver, and heart) were contoured in all 10 phases of planning 4D-CT scans for five patients who underwent abdominal radiotherapy. Planning target volumes (PTVs) encompassing all positions of the stomach (PTV(all phases)) were generated. Three respiratory phases for RGRT in inspiration and expiration were identified, and corresponding PTV(inspiration) and PTV(expiration) and OAR volumes were created. Landmark-based fields recommended for the Radiation Therapy Oncology Group (RTOG) 99-04 study protocol were simulated to assess PTV coverage. IMRT and 3D-CRT planning with and without additional RGRT planning were performed for all PTVs, and corresponding dose volume histograms were analyzed.


RESULTS
Use of landmark-based fields did not result in full geometric coverage of the PTV(all phases) in any patient. IMRT significantly reduced mean renal doses compared with 3D-CRT (15.0 Gy +/- 0.9 Gy vs. 20.1 Gy +/- 9.3 Gy and 16.6 Gy +/- 1.5 Gy vs. 32.6 Gy +/- 7.1 Gy for the left and right kidneys, respectively; p = 0.04). No significant increase in renal sparing was seen when adding RGRT to either 3D-CRT or IMRT. Tolerance doses to the other OAR were not exceeded.


CONCLUSIONS
Individualized field margins are essential for gastric irradiation. IMRT plans significantly reduce renal doses, but the benefits of RGRT in gastric irradiation appear to be limited.
van der Geld
Ylanga G
YG
Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands.
Senan
Suresh
S
van Sörnsen de Koste
John R
JR
Verbakel
Wilko F A R
WF
Slotman
Ben J
BJ
Lagerwaard
Frank J
FJ
D000704:Analysis of Variance; D004386:Duodenum / Q000528:radiation effects; D006321:Heart / Q000528:radiation effects; D006801:Humans; D007668:Kidney / Q000528:radiation effects*; D008099:Liver / Q000528:radiation effects; D009068:Movement; D011832:Radiation Injuries / Q000517:prevention & control*; D020266:Radiotherapy, Conformal; D050397:Radiotherapy, Intensity-Modulated; D012119:Respiration; D012189:Retrospective Studies; D013116:Spinal Cord / Q000528:radiation effects; D013270:Stomach / Q000528:radiation effects; D013274:Stomach Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D014057:Tomography, X-Ray Computed / Q000379:methods*