Dosimetric and Radiobiological Comparison of Five Techniques for Postmastectomy Radiotherapy with Simultaneous Integrated Boost

Abstract

Purpose. To compare five techniques for the postmastectomy radiotherapy (PMRT) with simultaneous integrated boost (SIB). Materials and Methods. Twenty patients with left-sided breast cancer were retrospectively selected. Five treatment plans were created for each patient: TomoDirect (TD), unblocked helical TomoTherapy (unb-HT), blocked HT (b-HT), hybrid intensity-modulated radiotherapy (hy-IMRT), and fixed-field IMRT (ff-IMRT). A dose of 50.4 Gy in 28 fractions to PTVtotal and 60.2 Gy in 28 fractions to PTVboost were prescribed. The dosimetric parameters for targets and organs at risk (OARs), the normal tissue complication probability (NTCP), the second cancer complication probability (SCCP) for OARs, and the treatment efficiency were assessed and compared. Results. TD plans and hy-IMRT plans had similar good dose coverage and homogeneity for both PTVboost and PTVtotal and superior dose sparing for the lungs and heart. The ff-IMRT plans had similar dosimetric results for the target volumes compared with the TD and hy-IMRT plans, but gave a relatively higher NTCP and SCCP for the lungs. The unb-HT plans exhibited the highest OAR mean dose, highest NTCP for the lungs (0.97±1.25‰) and heart (4.58±3.62%), and highest SCCP for the lungs (3.57±0.05%) and contralateral breast (2.75±0.29%) among all techniques. The b-HT plans significantly outperformed unb-HT plans with respect to the sparing of the lungs and heart. This technique also showed the best conformity index (0.73±0.08) for PTVboost and the optimal NTCP for the lungs (0.03±0.03‰) and heart (0.61±0.73%). Concerning the delivery efficiency, the hy-IMRT and ff-IMRT achieved much higher delivery efficiency compared with TomoTherapy plans. Conclusion. Of the five techniques studied, TD and hy-IMRT are considered the preferable options for PMRT with SIB for left-sided breast cancer treatment and can be routinely applied in clinical practice.

Improvement of helical tomotherapy treatment plan efficiency with block techniques for left-sided post-mastectomy radiation therapy

“…4,5 On the other hand, HT increases low-dose area and mean dose of OARs, high normal tissue complication probability for the lungs and heart, and high secondary cancer complication probability for the lungs and contralateral breast. 6 HT used without block structure has a potentially higher risk of radiation pneumonitis, cardiac disease and secondary cancer. 6 On the other hand, HT with a block structure increases the number of monitor units and treatment time (TT).…”

“…6 HT used without block structure has a potentially higher risk of radiation pneumonitis, cardiac disease and secondary cancer. 6 On the other hand, HT with a block structure increases the number of monitor units and treatment time (TT). [6][7][8] The trade-off between the TT and the plan quality should be balanced.…”

“…6 On the other hand, HT with a block structure increases the number of monitor units and treatment time (TT). [6][7][8] The trade-off between the TT and the plan quality should be balanced. 6 The reduction in TT may lead to improved treatment accuracy because the influence of intrafraction motion was reduced.…”

“…[6][7][8] The trade-off between the TT and the plan quality should be balanced. 6 The reduction in TT may lead to improved treatment accuracy because the influence of intrafraction motion was reduced. 9 Moreover, less TT could provide the opportunity for more patients to be treated earlier and improve the treatment efficiency.…”

Evaluation of robustness of optimization methods in breast intensity-modulated radiation therapy using TomoTherapy

“…Although skin ash cannot be used in helical TomoTherapy, in which rotational beam delivery is employed, it can be used for TomoDirect, in which beam delivery occurs at a xed gantry angle. TomoDirect is advantageous for breast radiation therapy because the low-dose spread to the lungs is reduced [21,22]. Kang et al reported that skin ash maintains coverage of the target in TomoDirect plans when a setup error occurs [23].…”