Four-dimensional CT-based evaluation of intrafractional and interfractional anastomosis motion during postoperative radiotherapy in gastric cancer : a prospective study

Abstract

Objective To study the intrafractional and interfractional anastomosis motion during postoperative adjuvant radiotherapy in gastric cancer by four-dimensional CT (4DCT) . Methods Eight patients with locally advanced gastric cancer who underwent Billroth I gastrectomy and postoperative radiotherapy were enrolled in this study and prospective analysis was performed. A total of four 4DCT, including simulation and repeating during radiation, were performed during free breathing and dietary restriction. The implanted anastomotic nail was used as the observational subject, and the intrafractional and interfractional anastomosis motion was evaluated in the right-left (RL) , anterior-posterior (AP) , and superior-inferior (SI) directions. The relationship between the volume change in remnant stomach and interfractional anastomosis motion was analyzed. The differences within and between groups were analyzed by paired t test and one-way ANOVA, respectively. Results The intrafractional anastomosis motion was (2.4±2.3) mm, (2.1±2.0) mm, and (5.6±4.0) mm in RL, AP, and SI directions, respectively, and the motion in SI direction was significantly greater than that in RL and AP directions (P=0.000 and 0.000). The interfractional anastomosis motion was (6.1±6.6) mm, (3.3±3.0) mm, and (4.8±4.3) mm in RL, AP, and SI directions, respectively, with no significant differences between different directions (P=0.064,0.156,0.161). In RL direction, the interfractional anastomosis motion was significantly greater than the intrafractional anastomosis motion (P=0.018). The internal margins accounting for respiration related displacement and interfractional variability were 24.2 mm, 10.3 mm, and 18.3 mm in RL, AP and SI directions, respectively. Conclusions The intrafractional and interfractional anastomosis motion should be considered during postoperative adjuvant radiotherapy in gastric cancer patients who have undergone Billroth I gastrectomy. The internal margins required for anastomosis in RL, AP and SI directions are 24.2mm, 10.3 mm and 18.3 mm, respectively. Key words: Tomography, X - ray computed, four - dimensional; Intrafractional displacement; Interfractional displacement; Gastric neoplasms/postoperative radiotherapy