20 Treating breast cancer with VMAT in deep inspiration breath hold: The Geneva experience

• Published in: Physica medica Vol. 56; pp. 12 - 13
• Main Authors: Dubouloz, A., Nouet, P., Koutsouvelis, N., Dipasquale, G., Jaccard, M., Fargier-Bochaton, O., Rouzaud, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2018
• ISSN: 1120-1797; 1724-191X
• DOI: 10.1016/j.ejmp.2018.09.033

We report on the treatment management and the dosimetric results of deep inspiration breath hold (DIBH) volumetric modulated arc therapy (VMAT) treatments for breast cancer patients. A total of sixty-four patients with breast cancer beneficiated from DIBH VMAT treatments since the implementation of this technique in our department in October 2016. The simulation CT (CTsim) room is equipped with the Real-time Position Management™ (RPM 1.7) Respiratory Gating (Varian) and the treatments are delivered on either a TrueBeam with Respiratory Gating or a Varian Linac with RPM. DIBH coaching is performed by the RTTs the day of CTsim. CTsim is acquired when the patient is able to maintain a reproducible and stable DIBH for at least 20 s. The “reference” breathing curve acquired at CTsim is saved, and personalized gating thresholds are defined for treatment delivery. The treatment is delivered using a 6 MV beam with 2 partial arcs (200°) and 2 “tangential-like” arcs (50°). For dosimetric analysis, patients were divided into 9 groups depending on the anatomical regions (breast and lymph nodes) included in the planning target volume (PTV), the breast laterality (50 left, 10 right and 4 double-sided irradiations) and the presence of a simultaneous integrated boost (SIB). The total dose was renormalized at the same value (50 Gy) for each group (4 different dose prescriptions and fractionations are used in Geneva). Patient setup is controlled with DIBH kV/kV and CBCT images. The RTTs need to continuously coach the patient as he cannot visualize its DIBH level during the session. Using DIBH technique requires additional time compared to a free breathing treatment (35 vs. 20 min per fraction). As for dosimetry, in all groups, more than 95% of the PTV received at least 95% of the prescribed dose. The dose received by 2% of the PTV did not exceed 107.3% for groups without SIB, and 111.4% for groups with SIB. Mean dose (Dmean) to the heart was 5 Gy for groups without internal mammary chain (IMC) irradiation, 6 Gy with IMC, and reached 8 Gy for double-sided breast and whole left breast with SIB irradiations. Dmean of the contralateral breast did not exceed 2.8 Gy for groups without IMC, and 3.8 Gy for groups with IMC. As for the contralateral lung: Dmean was 3 Gy and 5 Gy, V5Gy was 20% and 40%, for groups without and with IMC respectively. For the homolateral lung, Dmean was below 9.5 Gy for breast alone groups (+/-SIB) and 13.9 Gy for IMC + SIB groups, V5Gy was below 50% for breast alone groups, below 56.1 % for SIB groups, and below 78.7% for IMC + SIB groups. Radiotherapy treatment of breast cancer using DIBH and a VMAT technique is more and more used in our center because of the excellent achievable OAR dose sparing and the good reproducibility of patient positioning. The additional time resource needed for this treatment modality is compensated by the gain in treatment quality.