Postmastectomy radiotherapy for left-sided breast cancer patients: Comparison of advanced techniques

Abstract

Postmastectomy radiotherapy (PMRT) has been shown to improve the overall survival for invasive breast cancer patients, and many advanced radiotherapy technologies were adopted for PMRT. The purpose of our study is to compare various advanced PMRT techniques including fixed-beam intensity-modulated radiotherapy (IMRT), non-coplanar volumetric modulated arc therapy (NC-VMAT), multiple arc VMAT (MA-VMAT), and tomotherapy (TOMO). Results of standard VMAT and mixed beam therapy that were published by our group previously were also included in the plan comparisons. Treatment plans were produced for nine PMRT patients previously treated in our clinic. The plans were evaluated based on planning target volume (PTV) coverage, dose homogeneity index (DHI), conformity index (CI), dose to organs at risk (OARs), normal tissue complication probability (NTCP) of pneumonitis, lifetime attributable risk (LAR) of second cancers, and risk of coronary events (RCE). All techniques produced clinically acceptable PMRT plans. Overall, fixed-beam IMRT delivered the lowest mean dose to contralateral breast (1.56 ± 0.4 Gy) and exhibited lowest LAR (0.6 ± 0.2%) of secondary contralateral breast cancer; NC-VMAT delivered the lowest mean dose to lungs (7.5 ± 0.8 Gy), exhibited lowest LAR (5.4 ± 2.8%) of secondary lung cancer and lowest NTCP (2.1 ± 0.4%) of pneumonitis; mixed beam therapy delivered the lowest mean dose to heart (7.1 ± 1.3 Gy) and exhibited lowest RCE (8.6 ± 7.1%); TOMO plans provided the most optimal target coverage while delivering higher dose to OARs than other techniques. Both NC-VMAT and MA-VMAT exhibited lower values of all OARs evaluation metrics compare to standard VMAT. Fixed-beam IMRT, NC-VMAT, and mixed beam therapy could be the optimal radiation technique for certain breast cancer patients after mastectomy.

Cost-Effectiveness Analysis of Advanced Radiotherapy Techniques for Post-Mastectomy Breast Cancer Patients

“…it has been highly controversial if the additional cost of proton therapy is justified by the potential advantages, and our study shows proton therapy is only cost-effective for PMRT patients at a WTP threshold of 100,000 $/QALY although it confers the lowest risks of radiogenic side effects among all techniques. [5,8] There are several limitations of this study. First, there is a lack of clinical information on late toxicities from advanced PMRT techniques, and the well-defined risk models were used to estimate those risk values in our study.…”

“…For advanced PMRT techniques, the transition probabilities were largely lacking in the literature. In this study, probabilities of tumor coverage including local recurrence and metastasis after advanced PMRT were assumed to be the same as those after SOC PMRT, while probabilities of radiogenic side effects after advanced PMRT were calculated based on normal tissue complication probability (NTCP), [28] lifetime attributable risk (LAR) of second cancers [29,30] and risk of coronary events (RCE) [12,31] models for a 55-year-old cohort as we previously reported [5,8] (Table 2). We assumed that all lung and cardiac events start from year 11 after radiotherapy, [12,32] while contralateral breast events start from year 6 after radiotherapy.…”

“…for patients with advanced disease, supraclavicular and axillary nodes are treated with additional photon fields. [2] In the past decades, many advanced technologies had been used for PMRT and shown promising results, such as intensity-modulated radiation therapy (IMRT), [3] standard volumetric modulated arc therapy (STD-VMAT), [4] non-coplanar VMAT (NC-VMAT), [5] multiple arc VMAT (MA-VMAT), [5] Tomotherapy (TOMO), [4] bolus electron conformal therapy (BECT), [6] BECT mixed with IMRT and VMAT (MIXED), [7] and proton therapy , [8] each with different degrees of sophistication and cost. Target coverage provided by most of these technologies is comparable, while the dose to surrounding normal tissues varies greatly.…”

Cost-Effectiveness Analysis of Advanced Radiotherapy Techniques for Post-Mastectomy Breast Cancer Patients

“…it has been highly controversial if the additional cost of proton therapy is justi ed by the potential advantages, and our study shows proton therapy is only cost-effective for PMRT patients at a WTP threshold of 100,000 $/QALY although it confers the lowest risks of radiogenic side effects among all techniques. [5,8] It may lower the national cost of breast cancer care, and even a small progress in this direction can help relieve patient's burden and national healthcare pressure. The scarce healthcare resources can be saved and used in other aspects of patient care.…”

“…[1] The current standard of care (SOC) PMRT technique in the US is using conventional parallel-opposed tangent photon elds to treat the lateral chest wall plus oblique electron elds; for patients with advanced disease, supraclavicular and axillary nodes are treated with additional photon elds. [2] In the past decades, many advanced technologies had been used for PMRT and shown promising results, such as intensity-modulated radiation therapy (IMRT), [3] standard volumetric modulated arc therapy (STD-VMAT), [4] non-coplanar VMAT (NC-VMAT), [5] multiple arc VMAT (MA-VMAT), [5] Tomotherapy (TOMO), [4] bolus electron conformal therapy (BECT), [6] BECT mixed with IMRT and VMAT (MIXED), [7] and proton therapy , [8] each with different degrees of sophistication and cost. Target coverage provided by most of these technologies is comparable, while the dose to surrounding normal tissues varies greatly.…”