Publication

Abstract : Aim This study aimed to compare the dosimetric performance of helical Tomotherapy and C-arm linac–based VMAT in bilateral breast cancer, focusing on target coverage, skin and sternal dose, organ-at-risk (OAR) sparing, low-dose spillage, and delivery efficiency. Methods A retrospective paired analysis was performed on CT datasets from 46 patients with bilateral breast cancer. Each case was replanned using Tomotherapy and TrueBeam VMAT to the same prescription. Planning objectives followed institutional and ESTRO guidelines, with additional evaluation of sternal dose, cutaneous dose (including Rando phantom OSLD validation), and whole-body low-dose spread (V20–50%). Plan quality indices, monitor units (MUs), beam-on time, and patient-specific QA (Arc CHECK, 3%/2 mm gamma) were assessed. Results Both platforms achieved comparable target coverage by D95%. VMAT provided superior conformity (p < 0.05) and volumetric coverage, though Tomotherapy yielded slightly more homogeneous PTV dose.VMAT significantly reduced mean and maximum skin dose (−387 cGy and −286 cGy,respectively; p < 0.05) and sternal mean dose (−264 cGy; p < 0.05). Whole-body spillage at 20–50% isodose levels decreased by 18–29% with VMAT (all p < 0.05). Lung and heart metrics showed trade-offs: VMAT reduced V5–V10 but increased lung V20 and focal heart dose, all within clinical limits. MU output was ∼85%lower with VMAT, improving efficiency. QA pass rates exceeded 95% for both techniques. Conclusion Both techniques are clinically viable, but VMAT offers greater conformity, lower skin and sternal doses, reduced intermediate-dose bath, and higher efficiency.Tomotherapy provides more uniform PTV dose and, in selected scenarios, favourable cardiopulmonary sparing.Technique choice should be individualised based on anatomy, nodal intent, and clinical priorities.