Skin and lung toxicity in synchronous bilateral breast cancer treated with volumetric-modulated arc radiotherapy: a mono-institutional experience.

PURPOSE: To evaluate acute and late skin/subcutaneous toxicities and radiation-induced lung fibrosis (RILF) in patients treated with adjuvant radiotherapy (RT) for synchronous bilateral breast cancers (SBBC), after conservative surgery. METHODS/PATIENTS: Twenty-five patients were treated with volumetric-modulated arc therapy (VMAT/RapidArc®) on both breasts, and checked clinically for detecting RT toxicities during and after treatment. A high-resolution computed tomography (HRCT) was performed, for detecting RILF during follow-up. RESULTS: We registered acute Grade-1 skin toxicity in 18 patients (72%), while six patients (24%) experienced Grade-2 toxicity. No breath symptoms were reported during and after RT. Late Grade-1 subcutaneous toxicity and late Grade-2 skin toxicity were registered in four patients (16%) and one patient (4%), respectively, at a mean follow-up of 36 months. Grade-1 RILF was detected in six patients (30%). The median volume of fibrosis area was 6.5 cc (range 1.3-21.5 cc). The partial volumes receiving a specified dose (V20, V30, V40, and V50) in patients who developed lung fibrosis were significantly bigger than who did not (p < 0.01). We showed that the mean volume of the tumour boost of patients who developed fibrosis (77.7 cc) was not significantly different from the other patients (90.8 cc) (p = 0.5). CONCLUSION: The clinical impact of this technique is favourable, and this is the first clinical study showing RILF by HRCT in a setting of SBBC. Further study with larger accrual is mandatory.

Helical Tomotherapy of the breast: can thermoplastic immobilization improve the reproducibility of the treatment setup and the accuracy of the delivered dose?

PURPOSE: To evaluate the impact of thermoplastic mask immobilization in the setup reproducibility and delivered dose for Helical Tomotherapy (HT) of the breast/chest wall. METHODS: 16 patients treated with Accuray Hi-Art HT for breast-cancer were considered. Patients were positioned supine with arms extended above the head using Civco Wing Board (WB) system. In 50% of patients an Orfit thermoplastic mask was added in order to improve immobilization. Before each treatment fraction a megavoltage CT (MVCT) scan was taken and registered to the planning CT by experienced medical staff. The impact of thermoplastic mask was investigated analysing MVCT shift-roll data and MVCT dose distribution using Planned Adaptive software. RESULTS: In the analysed cases, the addition of thermoplastic mask had minor impact on the lateral, longitudinal and roll data distribution. Variance of vertical shifts was significantly reduced in the WB + Orfit group. Van Herk's margins were not affected by addition of thermoplastic immobilization. In both groups, target coverage (V95) and maximum dose (D1) were almost identical to planned values. D1 of organs at risk were not significantly different in the two groups. CONCLUSIONS: Analysis of shift-roll data shows no improvement in the group of patients immobilized with the addition of thermoplastic mask. Van Herk's margin is quite large (7-10 mm) in both groups evidencing the need to perform daily setup correction. The adapted dose distribution complies well with the planned one, showing that if MVCT is used before each treatment fraction, a 3 mm margin (setup component) for CTVs expansion could be adequate.