Abstract
Purpose: To examine the methods of radiation treatment planning for gastric lymphoma. Materials and Methods: Twenty-six patients who underwent radiotherapy for gastric lymphoma between February 2000 and April 2005 were included in the study. Radiation doses were 30–40.5 Gy (median: 30) with a daily fraction size of 1.5 Gy. We considered that the volume irradiated with 20 Gy or more in the bilateral kidneys (K-V20) may be reduced to 50% or less. Anterior-posterior/posterior-anterior parallel-opposed fields (AP/PA) were compared retrospectively with the 4-field technique in 12 patients whose simulation data could be reconstructed in the radiation treatment planning system. Results: Twenty-four patients were treated with AP/PA, one patient with 4-field and one patient with 3-field. The predefined rules in margin-setting were not observed in 7 patients (27%) to reduce the irradiated volume of the kidney. Twenty-two patients achieved complete remission, and the overall 2-year survival rate was 95%. No late adverse events were seen. Our retrospective comparison of AP/PA with the 4-field technique in the radiation planning system indicated that K-V20 became more than 50% in 4 patients treated with AP/PA, but in none of those treated with the 4-field technique. In all 8 patients with K-V20 of less than 50% with AP/PA, the caudal side of the stomach was located above the mid-slice of the left kidney on abdominal CT. Conclusion: The outcome of gastric lymphoma after radiotherapy is excellent. When the position of the stomach is low relative to that of the left kidney, the 3D-based 4-field technique may allow realization of optimal radiation therapy ensuring sufficient margins of the target and increased safety for the kidney.
