Target coverage of daily cone-beam computed tomography in breath-hold image-guided radiotherapy for gastric lymphoma

OBJECTIVES: We evaluated retrospectively the daily target coverage using cone-beam computed tomography (CBCT) in breath-hold image-guided radiotherapy (BH-IGRT) for gastric lymphoma. METHODS: BH-IGRT was performed using a prescribed dose of 30.6 Gy in 17 fractions for the whole stomach. We assessed the target coverage of the whole stomach on daily CBCT images [daily clinical target volume (CTV)], which was delineated individually by two observers. We evaluated V(95%) (percentage of volume receiving ≥95% of the prescribed dose) of daily CTV. RESULTS: In total, 102 fractions from 6 patients were assessed. The mean V(95%) of daily CTV was 97.2%, which was over 95%. In two of six patients, the V(95%) of daily CTV was over 95% for either observer in all fractions. One patient had significant interobserver variation (p = 0.013). In 95 fractions (93%), the V(95%) of daily CTV was over 95% for either observer. CONCLUSION: Daily target coverage for CTV in BH-IGRT for gastric lymphoma seems to be favorable, even when using CBCT. ADVANCES IN KNOWLEDGE: A previous study ascertained good daily target coverage in BH-IGRT for gastric lymphoma using in-room CT. Even when using CBCT in our study, daily target coverage for CTV in BH-IGRT for gastric lymphoma seems to be favorable.