Spot-Scanning Proton Arc Therapy (Sparc) for Left-Sided Breast Irradiation

44 Background: Whole breast irradiation is an essential treatment after breast conserving surgery (BCS). Adverse effects are from inhomogeneity of PTV and excessive dose to normal tissues. Aim of this study is to compare dosimetry among standard technique, three-dimensional Conformal Radiotherapy (3D-CRT) and advanced techniques, Electronic Compensator (ECOMP), Intensity Modulated Radiation Therapy (IMRT) and Volumetric Arc Therapy (VMAT). Methods: Images from CT simulation of patients who underwent BCS were replanned. Clinical Target Volume (CTV) was contoured followed RTOG atlas as breast only and breast with chest wall respectively. Planning Target Volume (PTV) was expanded 0.7 cm from CTV. Each patient was replanned with all four techniques. Dose prescription was 50 Gy in 25 fractions. Results: Twenty five patients underwent CT simulation from November 2013 to November 2014 were included. Six patients with node positive were planned for breast with chest wall irradiation and 19 patients with node negative were planned for breast only irradiation. Primary outcome, homogeneity index (HI) of 3D-CRT, ECOMP, IMRT and VMAT were 0.865, 0.889, 0.890 and 0.866 respectively which ECOMP and IMRT were significant higher than 3D-CRT (p values < 0.001). Secondary outcome, conformity index (CI), Mean heart dose (MHD), heart V25, heart V30, mean lung dose (MLD), mean ipsilaterallung dose (MILD), mean contralateral lung dose (MCLD) and mean contralateral breast dose (MCBD) of advanced techniques were significant better than 3D-CRT technique. Conclusions: HI of ECOMP and IMRT were statistically significant higher compared with 3D-CRT technique. Advanced techniques showed statistically significant superior in CI dose to heart, lungs and contralateral breast.

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Is synchronous bilateral breast irradiation using flattening filter-free beam-based volumetric-modulated arc therapy beneficial? A dosimetric study

Journal of Medical Physics ◽

10.4103/jmp.jmp_32_20 ◽

2020 ◽

Vol 45 (4) ◽

pp. 226

Author(s):

K Veluraja ◽

Jagadheeskumar Nagaraj

Keyword(s):

Volumetric Modulated Arc Therapy ◽

Breast Irradiation ◽

Flattening Filter Free ◽

Arc Therapy ◽

Dosimetric Study ◽

Flattening Filter ◽

Free Beam

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Feasibility study: Spot-scanning Proton Arc therapy (SPArc) for left-sided breast irradiation

10.21203/rs.3.rs-38925/v1 ◽

2020 ◽

Author(s):

Sheng Chang ◽

Gang Liu ◽

Lewei Zhao ◽

Joshua T Dilworth ◽

Weili Zheng ◽

...

Keyword(s):

Breast Cancer ◽

Proton Therapy ◽

Normal Tissue ◽

Breast Irradiation ◽

Ipsilateral Lung ◽

Intensity Modulated Proton Therapy ◽

Intensity Modulated ◽

Spot Scanning ◽

Proton Treatment ◽

Beam Delivery

Abstract Background This study investigated the feasibility and potential clinical benefit of utilizing a new proton treatment technique: Spot-scanning Proton Arc (SPArc) therapy for left-sided breast cancer irradiation to further reduce radiation dose to healthy tissue and mitigate the probability of normal tissue complications compared to conventional Intensity Modulated Proton Therapy(IMPT). Methods Eight patients diagnosed with left-sided breast cancer and treated with breast-preserving surgery followed by whole breast irradiation without regional nodal irradiation were included in this retrospective planning. Two proton treatment plans were generated for each patient: vertical intensity-modulated proton therapy used for clinical treatment (vIMPT, gantry angle 10°-30°) and SPArc for comparison purpose. Both SPArc and vIMPT plans were optimized using the robust optimization of ± 3.5% range and 5 mm setup uncertainties. Root-mean-square deviation dose (RMSD) volume histograms were used for plan robustness evaluation. All dosimetric results were evaluated based on dose-volume histograms (DVH), and the interplay effect was evaluated based on the accumulation of single-fraction 4D dynamic dose on CT50. The treatment beam delivery time was simulated based on a gantry rotation with energy-layer-switching-time (ELST) from 0.2 to 5 s. Results The average D1 to the heart and LAD were reduced to 53.63 cGy and 82.25 cGy compared with vIMPT 110.38 cGy (p = 0.001) and 170.38 cGy (p = 0.001), respectively. The average V5Gy and V20Gy of ipsilateral lung was reduced to 16.77% and 3.07% compared to vIMPT 25.56% (p = 0.001) and 4.68% (p = 0.003). Skin3mm mean and maximum dose was reduced to 3999.38 cGy and 4395.63 cGy compared to vIMPT 4104.25 cGy (p = 0.039) and 4411.63 cGy (p = 0.043), respectively. A significant relative risk reduction (RNTCP = NTCPSPArc / NTCPvIMPT) for organs at risk (OARs) was obtained with SPArc ranging from 0.61 to 0.86 depending on the clinical endpoint. The RMSD Volume Histogram(RVH) analysis shows SPArc provided better plan robustness in OARs sparing, including the heart, LAD, ipsilateral lung, and skin. The average estimated treatment beam delivery times were comparable to vIMPT plans when the ELST is about 0.5 s. Conclusion SPArc technique can further reduce dose delivered to OARs and the probability of normal tissue complications in patients treated for left-sided breast cancer.

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