2044 - Comparison of Radiation-Induced Side Effects in Breast Cancer Treatments with the Application of 3D-Printed Immobilization Devices
Presenter(s)
A. Cicchetti1, T. Rancati1, C. Fiorino2, M. M. Aspradakis3, A. Clivio3, M. Staudacher4, J. W. Uiterwijk5, R. Ruggieri6, C. De Marco7, M. Fargier-Voiron7, M. Jaccard7, L. Nicosia6, A. Romei6, G. Gruber4, F. Alongi6,8, O. Matzinger7,9, D. R. Zwahlen3, and G. Dipasquale5; 1Fondazione IRCCS Istituto Nazionale dei Tumori, Data Science Unit, Milan, Italy, 2IRCCS San Raffaele Scientific Institute, Milan, Italy, 3Department of Radiation Oncology, Kantonsspital Winterthur, Winterthur, Switzerland, 4Institute for Radiotherapy, Klinik Hirslanden, Zurich, Switzerland, 5HeroSupport SA, Geneva, Switzerland, 6Department of Advanced Radiation Oncology, IRCCS Sacro Cuore Don Calabria Hospital, Cancer Care Center, Negrar di Valpolicella, Italy, 7Department of Radiation Oncology, Clinique de Genolier, Genolier, Switzerland, 8University of Brescia, Brescia, Italy, 9Health Science and Technology, ETH Zurich, Zurich, Switzerland
Purpose/Objective(s): This study analyzes the impact of a new 3D-printed immobilization device (shell) in full-breast irradiation through the comparison of Normal Tissue Complication Probability (NCTP) dose-response models for acute and late tissue effects. In this analysis, we tested the dose distributions on an anthropomorphic phantom treated for breast radiotherapy (RT).
Materials/Methods: The breast plans were designed on three radiotherapy systems using 6MV, 6FFFMV, 7MV and 10MV beams. A RANDO phantom was used for CT scans, with two different configurations: no shell and with shell. PTVs were adjusted by cropping 3mm from the skin, with a prescribed dose of 40.05Gy administered in 15 fractions, sparing the lungs using IMRT tangential fields technique. To predict skin dose and, consequently, the risk for RT-induced complications, we analyzed the DVHs of the “skin” defined as a 5mm inner isotropic expansion of the body. We applied 5 different NCTP models for grade=2 toxicity which have been published and validated on more than 700 patients: two models for acute skin reactions (one based on V20Gy and one on the dose to 20cc of the skin), two models for late edema (one based on V20Gy and one considering V20Gy & V42Gy) and a model for Liponecrosis (based on V30Gy). All the models were developed in the scheme of 40.05Gy in 15 fractions. The results report the absolute differences for the considered endpoints: differences in volumes (?V) and in NTCP (?NTCP).
Results: Eight treatment plans were generated. We extracted DVHs for the 5 mm skin and consequently V20Gy, V30Gy, V42Gy and the dose to 20cc of the structure. We didn’t apply any BED/EQD2Gy conversions since we delivered treatments with the same fractionation of the model development cohorts.
Table 1 reports the differences in dose-volume parameters for the five NTCP models and the variation in risk prediction probability computed as (“Shell value” - “breast only value”). The shell showed comparable dose metrics (?V <15cc) and probability risks (?NTCP <2%) in the 4 treatment modalities with the only exception of V30Gy and grade=2 Liponecrosis. Interestingly, no variations were found in the high-dose region of the skin DVH.Conclusion: In the study context, the 3D-printed shell demonstrated dose distributions comparable to those of the standard treatment in the analyzed variables. Further analyses will be conducted with Accelerated Partial Breast Irradiation and to see if NTCP can guide optimization of skin doses.
Abstract 2044 - Table 1| Acute Reactions Models | Edema | Late Effects | Liponecrosis | ||||
| V20Gy | *Dose to 20cc | V20Gy | V20Gy & V42Gy | V30Gy | |||
| ?V / ?NTCP | ?V / ?NTCP | ?V / ?NTCP | ?V20Gy | ?V42Gy | ?NTCP | ?V / ?NTCP | |
| MRI linac | 8cc / 1.2% | 0.2Gy / 0% | 8cc / 0.5% | 8cc | -0.9cc | 0.3% | 27cc / 3.5% |
| 6V linac | 11cc / 1.6% | 0.9 Gy / 1.7% | 11cc / 0.7% | 11cc | 0cc | 0.5% | 51cc / 7.2% |
| 10V linac | 15.5c c / 2.2% | 0.6Gy / 1.2% | 15.5cc / 1% | 15.5cc | 0cc | 0.6% | 62cc / 7.9% |
| helical linac | -8cc / -1.1% | 0.6Gy / 1.2% | -8cc / -0.5% | -8cc | 0.01cc | 0.3% | 18.5cc / 2.8% |
| *model includes dose boost |