Accelerated partial breast irradiation using robotic radiotherapy: a dosimetric comparison with tomotherapy and three-dimensional conformal radiotherapy

Abstract

BackgroundAccelerated partial breast irradiation (APBI) is a new breast treatment modality aiming to reduce treatment time using hypo fractionation. Compared to conventional whole breast irradiation that takes 5 to 6 weeks, APBI is reported to induce worse cosmetic outcomes both when using three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT). These late normal tissue effects may be attributed to the dose volume effect because a large portion of the non-target breast tissue volume (NTBTV) receives a high dose. In the context of APBI, non-coplanar beams could spare the NTBTV more efficiently. This study evaluates the dosimetric benefit of using the Cyberknife (CK) for APBI in comparison to IMRT (Tomotherapy) and three dimensional conformal radiotherapy (3D-CRT).MethodsThe possibility of using surgical clips, implanted during surgery, to track target movements is investigated first. A phantom of a female thorax was designed in-house using the measurements of 20 patients. Surgical clips of different sizes were inserted inside the breast. A treatment plan was delivered to the mobile and immobile phantom. The motion compensation accuracy was evaluated using three radiochromic films inserted inside the breast. Three dimensional conformal radiotherapy (3D-CRT), Tomotherapy (TOMO) and CK treatment plans were calculated for 10 consecutive patients who received APBI in Lille. To ensure a fair comparison of the three techniques, margins applied to the CTV were set to 10 mm. However, a second CK plan was prepared using 3 mm margins to evaluate the benefits of motion compensation.ResultsOnly the larger clips (VITALITEC Medium-Large) could be tracked inside the larger breast (all gamma indices below 1 for 1 % of the maximum dose and 1 mm). All techniques meet the guidelines defined in the NSABP/RTOG and SHARE protocols. As the applied dose volume constraints are very strong, insignificant dosimetric differences exist between techniques regarding the PTV coverage and the sparing of the lung and heart. However, the CK may be used to reduce high doses received by the NTBTV more efficiently.ConclusionsRobotic stereotactic radiotherapy may be used for APBI to more efficiently spare the NTBTV and improve cosmetic results of APBI.

Partial breast irradiation with CyberKnife after breast conserving surgery: a pilot study in early breast cancer

“…Furthermore, the fiducial-based synchrony tracking method used by CyberKnife allows adding a minimal margin to CTV when creating PTV, allowing for greater spare of skin surface, chest wall, and pectoralis muscles. In general, we used a greater margin between CTV and PTV than that considered by Rault et al [ 29 ]: however our PTV dimensions were consistent with other experiences [ 30 , 38 ], but to reduce the skin dose we often applied a smaller margin near the skin to keep a margin of 5 mm between skin and PTV. Moreover, CyberKnife offers the possibility to fractionate the dose through a large number of beams (in our experience from 56 to 325) allowing distribution of the skin dose on a larger area, making the treatment more acceptable.…”

“…All authors comparing CyberKnife versus other techniques, i.e. 3D-CRT, IMRT and tomotherapy, concluded that CyberKnife can achieve a highest level of PTV coverage and, generally, the deepest dose gradient with better dose sparing of organs at risk and, in particular, of the homolateral breast [ 27 – 29 , 39 ]. Consequently, the involved tissue volume can be reduced by treatment with CyberKnife [ 27 , 28 ].…”

Comprehensive target geometric errors and margin assessment in stereotactic partial breast irradiation

“…Accelerated partial breast irradiation (APBI) is an effective alternative to standard whole breast irradiation (WBI) in selected early-stage breast cancer patients undergoing breast conservation therapy [ 1 – 6 ]. Recently developed stereotactic partial breast irradiation (S-PBI) allows 1–5 treatment fractions by delivering a high biologically potent dose to the target, while sparing adjacent critical organs and normal tissue [ 1 , 7 – 9 ]. With S-PBI tumoricidal doses, accurate and precise dose delivery is critical to achieve high treatment quality.…”

Dosimetric comparison between helical tomotherapy and intensity‐modulated radiotherapy for esophageal carcinoma

“…Helical tomotherapy is a modality of IMRT delivered by a continuously moving slip ring gantry in synchrony with the couch motion, and with a fan radiation beam modulated by a binary multi‐leaf collimator. The application of mega‐voltage computed tomography (CT) provides a viable solution to adaptive radiotherapy and dose‐guided radiotherapy …”