Prospective study evaluating the impact of deep inspiratory breath hold in the treatment of right-sided breast cancer with regional nodal irradiation

Deep Inspiratory breath hold (DIBH) is a well-established technique for minimizing cardiac and pulmonary radiation exposure in left-sided breast cancer, yet its application and benefits for right-sided breast cancer have limited data. This study investigates the effects of DIBH in comparison to free breathing (FB) in right-sided breast cancer patient, with a focus on its impact with regional nodal irradiation (RNI). materials-methods: We conducted a prospective study from November 2023 to October 2024 on patients with right-sided breast cancer requiring irradiation to the breast or chest wall, including regional lymph nodes (supraclavicular lymph nodes, axilla, or internal mammary lymph nodes (IMNs)). For each patient, two treatment plans were generated, one using FB and the other using DIBH, of which 3 patients were planned using Volumetric Modulated Arc Therapy (VMAT) and 27 patients were planned using Three-Dimensional Conformal Radiotherapy (3DCRT) with tangential beam technique. Dose-volume histograms (DVHs) were used to evaluate key dosimetric parameters: mean lung dose, ipsilateral lung V20, V16, and V5 (volumes receiving ≥20 Gy, ≥16 Gy, and ≥5 Gy, respectively), liver V20 and V30 (volumes receiving ≥20 Gy and ≥30 Gy, respectively), liver Dmax, mean heart dose, heart V25 and V5 (volumes receiving ≥25 Gy and ≥5 Gy, respectively), and coverage of the IMNs clinical target volume (CTV) and planning target volume (PTV) at 95 % and 90 %. Dosimetric comparisons between DIBH and FB were performed and the correlation between these differences and patient related parameters were analyzed using multiple linear regression. A comparison of 60 FB and DIBH plans on 30 patients revealed significant reductions in ipsilateral lung and liver dose parameters with DIBH. The mean lung dose decreased from 14 Gy to 10 Gy (P < 0.0001), V20 from 31 % to 16 % (P < 0.0001), V16 from 32 % to 21 % (P < 0.0001), and V5 from50 % to 41 % (P < 0.0001). Liver Dmax was reduced from 40 Gy to 20 Gy (P < 0.0001), V20 from 0.43 % to 0.00 % (P < 0.0001), and V30 from 0.07 % to 0.00 % (P < 0.0001). For the heart, the mean dose decreased from 1 Gy to 0.84 Gy (P < 0.0001), and V5 decreased from 0.005 % to 0.00 % (P = 0.0016), while heart V25 remained unchanged (P > 0.9999). No significant improvements were observed in IMN CTV and PTV coverage with DIBH. The differences in the after mentioned dosimetry parameters between FB and DIBH did not seem to correlate with any patient or treatment characteristics. Out of the 30 patients included in the study, 46.7 % received IMN irradiation. IMN irradiation was significantly associated with a greater difference in mean heart dose between FB and DIBH techniques. (0.36 Gy; p = 0.02). DIBH in radiotherapy for right-sided breast cancer with regional lymph node involvement offers significant dosimetry benefits, notably reducing radiation exposure to the heart, lungs and liver. These advantages make DIBH the preferred technique for treating right-sided breast cancer with nodal irradiation, especially when the ipsilateral IMNs are targeted.