en Radiation Biology Radiation Biology تحقيق بديع Original Research <div style="text-align: justify;"><span style="font-size:10pt"><span style="text-justify:newspaper"><span style="text-kashida-space:50%"><span style="line-height:119%"><span style="font-family:Calibri"><span style="color:black"><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Background:</span></span></span></span></span></span> <span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:black"><span style="language:en-GB">This study assessed the dosimetric implications of a reduced-frequency bolus regimen combined with treatment plan reoptimization in post-mastectomy radiotherapy (PMRT), with the goal of optimizing target coverage and organ-at-risk (OAR) dose sparing. </span></span></span></span><span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-GB">Materials and Methods: </span></span></span></span></span></span><span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:black"><span style="language:en-GB">Eighteen post-mastectomy patients scheduled for radiotherapy were enrolled. CT simulation was performed without bolus. A baseline plan (Plan(all)) was created using a virtual bolus to meet clinical objectives. Two derivative plans were generated from Plan(all): Plan (nobolus)- direct bolus removal without re-optimization and Plan(nobolus-new)- re-optimized after bolus removal to enhance target coverage. Three hybrid 25-fraction plans were generated by combining fractions of Plan(all) and Plan (nobolus): Plan(20bolus) (20 fractions Plan(all)+5 fractions Plan(nobolus)), Plan(18bolus)(18+7), and Plan(13bolus)(13+12). Similarly, three additional hybrid plans were constructed by combining Plan(all) with Plan(nobolus-new): Plan(20bolus-new), Plan(18bolus-new) and Plan(13bolus-new). Dosimetric parameters were compared across all plans. </span></span></span></span><span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-GB">Results: </span></span></span></span></span></span><span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:black"><span style="language:en-GB">Compared with Plan(nobolus), Plan(nobolus-new) offered improved target coverage, reduced high-dose volumes within the target, and enhanced dose homogeneity, albeit at the expense of elevated doses to the lungs, heart, and skin. Notably, Plan(13bolus-new) achieved comparable skin dose (body2mm/D10cc: 50.19&plusmn;1.33 Gy vs 50.19&plusmn;0.46 Gy, P>0.05) and high-dose target volume (PTV/D2%: 52.95&plusmn;0.25 Gy vs 52.99&plusmn;0.20 Gy, P>0.05) relative to the Plan(20bolus), while yielding statistically superior target coverage (PTV/V95%p: 96.59&plusmn;1.86% vs 97.36 &plusmn;1.53%, P<0.05). </span></span></span></span><span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-GB">Conclusion: </span></span></span></span></span></span><span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:black"><span style="language:en-GB">A reduction in bolus application frequency compromises target coverage yet attenuates skin dose. A strategy combining reduced bolus frequency with plan reoptimization represents a feasible approach to minimize bolus use while preserving both target coverage and skin dose parameters.</span></span></span></span></span></span></span></span></span></span></div> Post-radical mastectomy radiotherapy, bolus, plan design, plan dosimetry. 509 514 http://ijrr.com/browse.php?a_code=A-10-1-1526&slc_lang=en&sid=1 Z. Shan 7900319475328460033657 7900319475328460033657 No Department of Radiotherapy, Luohu People’s Hospital, Shenzhen, 518000, China F. Zhou fszl2025@163.com 7900319475328460033658 7900319475328460033658 Yes Department of Radiotherapy, Luohu People’s Hospital, Shenzhen, 518000, China