Optimizing and assessing the clinical effectiveness of deep-inspiration breath hold compared to free breathing in radiotherapy for gastric lymphoma.

Abstract

416 Background: Variable anatomy, prompted by bowel filling and respiratory motion, necessitates larger margins for planning target volumes (PTV) in radiotherapy for gastric lymphoma patients, leading to higher doses to organs at risk (OAR). The deep inspiratory breath-holding (DIBH) technique during radiotherapy has emerged as a protective method that improves OAR sparing. Therefore, this systematic review aims to systematically evaluate the benefits of DIBH compared to free breathing (FB) techniques during radiotherapy for gastric lymphomas, along with the physiological mechanisms involved. Methods: This systematic review included three comparative studies following a comprehensive search across PubMed, Google Scholar, and the Cochrane Library, involving a total of 33 patients with gastric lymphomas, in whom radiotherapy was planned under both DIBH and FB. The radiotherapeutic techniques assessed were intensity-modulated radiotherapy (IMRT), 3D-conformal radiotherapy (3D-CRT), step-and-shoot IMRT (SIMRT), volumetric-modulated arc therapy (VMAT), and tomotherapy. The dosimetric parameters included Gy (Gray), mean dose (Dmean), maximum dose (Dmax), etc. Results: Median heart dose (MHD) showed a consistent and significant reduction with DIBH across all techniques, including IMRT: 4.9→2.6 Gy; 3D: 8.54→4.46 Gy; SIMRT: 6.97→3.63 Gy; VMAT: 6.83→3.42 Gy; and tomotherapy: 7.06→3.80 Gy (all p<0.001). An additional study reported a decline from 7.1 Gy (FB 1.5 cm PTV) to 3.2 Gy (DIBH 1 cm PTV) (p<0.001). Kidney doses showed modest changes, with Dmean reduced from 4.3 Gy with FB 1 cm to 3.8 Gy with DIBH. For the left kidney, only one study demonstrated a significant reduction (p = 0.01). Spinal cord doses were also lower with DIBH; Dmax decreased from 19.79 to 17.56 Gy (VMAT), and Dmean from 8.7 Gy (FB 1.0 cm) and 9.7 Gy (FB 1.5 cm) to 7.9 Gy (DIBH) (p=0.02 and p=0.001). Findings in the lung were inconsistent: one study reported lower Dmean with DIBH, while others noted slight increases, e.g., left lung 3.0 vs. 2.6 Gy for FB 1 cm; 3.3 vs. 3.0 Gy for FB 1.5 cm. Liver outcomes were non-significant primarily, with reported reductions from 9.4 to 8.3 Gy and 13.91 to 12.64 Gy, although one study showed a higher Dmean with DIBH compared to FB 1 cm (p = 0.04). Conclusions: In conclusion, based on the current literature, DIBH significantly improves organ at risk (OAR) sparing, especially for the heart, right kidney, and spinal cord, during radiotherapy for gastric lymphomas. While results for the liver and lungs are mixed, no significant differences have yet been reported for the small bowel. These findings support the routine use of DIBH to minimize cardiac and critical organ radiation during radiotherapy, thereby facilitating safer clinical and patient practices.