Incorporating breath holding and image guidance in the adjuvant gastric cancer radiotherapy: a dosimetric study

Abstract

BackgroundThe respiratory related target motion and setup error will lead to a large margin in the gastric radiotherapy. The purpose of this study is to investigate the dosimetric benefit and the possibility of incorporating the breath-hold (BH) technique with online image-guided radiotherapy in the adjuvant gastric cancer radiotherapy.MethodsSetup errors and target motions of 22 post-operative gastric cancer patients with surgical clips were analyzed. Clips movement was recorded using the digital fluoroscopics and the probability distribution functions (pdf) of the target motions were created for both the free breathing (FB) and BH treatment. For dosimetric comparisons, two intensity-modulated radiotherapy (IMRT) treatment plans, i.e. the free breathing treatment plan (IMRTFB) and the image-guided BH treatment plan (IMRTIGBH) using the same beam parameters were performed among 6 randomly selected patients. Different margins for FB and BH plans were derived. The plan dose map was convoluted with various pdfs of the setup errors and the target motions. Target coverage and dose to organs at risk were compared and the dose-escalation probability was assessed.ResultsThe mean setup errors were 1.2 mm in the superior-inferior (SI), 0.0 mm in the left-right (LR), and 1.4 mm in the anterior-posterior (AP) directions. The mean target motion for the free breathing (vs. BH) was 11.1 mm (vs. 2.2 mm), 1.9 mm (vs. 1.1 mm), and 5.5 mm (vs. 1.7 mm) in the SI, LR, and AP direction, respectively. The target coverage was comparable for all the original plans. IMRTIGBH showed lower dose to the liver compared with IMRTFB (p = 0.01) but no significant difference in the kidneys. Convolved IMRTIGBH showed better sparing in kidneys (p < 0.01) and similar in liver (p = 0.08).ConclusionsCombining BH technique with online image guided IMRT can minimize the organ motion and improve the setup accuracy. The dosimetric comparison showed the dose could be escalated to 54 Gy without increasing the critical organs toxicities, although further clinical data is needed.

Passive breath gating equipment for cone beam CT-guided RapidArc gastric cancer treatments

“…We used a total margin of 7 mm in all directions to ensure adequate target coverage. This margin was originally derived from our previous study with the active breath hold technique [9]. Additionally, rotational errors also contributed to the uncertainties, and they were prominent in those fractions where maximum (7-8 mm) variations in the SI direction were observed.…”

“…In our earlier planning study [9] we compared dosimetric consequences of treatment delivery in free breathing and breath hold in the 75% phase of deep inspiration. Treatments delivered with breath hold and online image guidance allowed an increase in target dose from 45 Gy to 54 Gy while maintaining comparable dose distribution in critical organs However, dose delivery using breath hold requires purchasing additional equipment, such as active breathing control (ABC) devices, which can be costly and difficult to integrate with the linac.…”

Chemoradiation for gastric cancer: controversies, updates and novel techniques

“…The mean target motion for free breathing vs breathhold using ABC was 11.1 vs 2.2 mm, 1.9 vs 1.1 mm and 5.5 vs 1.7 mm in the SI, LR and AP directions, respectively. 53 A dosimetric study indicated that IMRT performed using breathhold could reduce the liver dose than IMRT with free breathing. 53 Hu et al 53 developed a passive breath-hold device and showed, in a pre-clinical study, that the diaphragm motion caused by respiration was reduced to ,3 mm, and the diaphragm position in different gating periods was reproducible.…”

“…53 A dosimetric study indicated that IMRT performed using breathhold could reduce the liver dose than IMRT with free breathing. 53 Hu et al 53 developed a passive breath-hold device and showed, in a pre-clinical study, that the diaphragm motion caused by respiration was reduced to ,3 mm, and the diaphragm position in different gating periods was reproducible. Another option of the breath-hold device is abdominal compression.…”

“…Conventional fluoroscopic imaging is used extensively as a simple way to track the diaphragm or fiducial markers to determine the target motion, 53,54 which is used as a reference for determining the margin of the planning target volume. Conventional CT in free breathing mode is associated with respiratory-related artefacts, leading to uncertainty about the position and volume of the target.…”