Purpose: To assess the potential advantage of intensity-modulated radiotherapy (IMRT) over conformal planning for postoperative adjuvant radiotherapy in patients with gastric carcinoma.
Methods and materials: Twenty patients who had undergone treatment planning with conformal beam arrangements for 4500 cGy adjuvant radiotherapy between 2000 and 2001 underwent repeat planning using IMRT techniques. Conformal five-field plans were compared with seven- to nine-field coplanar sliding-window IMRT plans. For each patient, the cumulative dose-volume histograms and organ-dose summaries (without distributions or digitally reconstructed radiographs) were provided to two independent, "blinded" GI radiation oncologists. The oncologists indicated which plan provided better planning target volume coverage and critical organ sparing, any safety concerns with either plan, and which plan they would choose to treat the patient.
Results: In 18 (90%) of 20 cases, both oncologists chose the same plan. Cases with disagreement were given to a third "blinded" reviewer. A "preferred plan" could be determined in 19 (95%) of 20 cases. IMRT was preferred in 17 (89%) of 19 cases. In 4 (20%) of 20 IMRT plans at least one radiation oncologist had safety concerns because of the spinal cord dose (3 cases) or small bowel dose (2 cases). Of 42 ratings, IMRT was thought to provide better planning target volume coverage in 36 (86%) and better sparing of the spinal cord in 31 (74%) of 42, kidneys in 29 (69%), liver in 30 (71%), and heart in 29 (69%) of 42 ratings. The median underdose volume (1.7 vs. 4.1 cm3), maximal dose to the spinal cord (36.85 vs. 45.65 Gy), and dose to 50% of the liver (17.29 vs. 27.97), heart (12.89 vs. 15.50 Gy), and left kidney (15.50 vs. 16.06 Gy) were lower with IMRT than with the conformal plans.
Conclusion: Compared with the conformal plans, oncologists frequently preferred IMRT plans when using dose-volume histogram data. The advantages of IMRT plans include both improved planning target volume coverage and improved sparing of critical organs. We are currently studying organ motion in the upper abdomen as a prerequisite to using IMRT for actual patient treatment.