Potential skin morbidity reduction with intensity-modulated proton therapy for breast cancer with nodal involvement
Creators: name: Fellin, Francesco
name: Iacco, Martina
name: D'Avino, Vittoria
name: Tommasino, Francesco
name: Farace, Paolo
name: Palma, Giuseppe
name: Conson, Manuel
name: Giacomelli, Irene
name: Zucchetti, Claudio
name: Falcinelli, Lorenzo
name: Amichetti, Maurizio
name: Aristei, Cynthia
name: Cella, Laura
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: Space Science
subject: 29999 Physical Sciences not elsewhere classified
subject: FOS: Physical sciences
subject: FOS: Physical sciences
subject: Medicine
subject: Molecular Biology
subject: Physiology
subject: FOS: Biological sciences
subject: FOS: Biological sciences
subject: 69999 Biological Sciences not elsewhere classified
subject: Cancer
subject: Computational Biology

description: <b>Background:</b> Different modern radiation therapy treatment solutions for breast cancer (BC) and regional nodal irradiation (RNI) have been proposed. In this study, we evaluate the potential reduction in radiation-induced skin morbidity obtained by intensity modulated proton therapy (IMPT) compared with intensity modulated photon therapy (IMXT) for left-side BC and RNI. <b>Material and Methods:</b> Using CT scans from 10 left-side BC patients, treatment plans were generated using IMXT and IMPT techniques. A dose of 50 Gy (or Gy [RBE] for IMPT) was prescribed to the target volume (involved breast, the internal mammary, supraclavicular, and infraclavicular nodes). Two single filed optimization IMPT (IMPT<sub>1</sub> and IMPT<sub>2</sub>) plans were calculated without and with skin optimization. For each technique, skin dose-metrics were extracted and normal tissue complication probability (NTCP) models from the literature were employed to estimate the risk of radiation-induced skin morbidity. NTCPs for relevant organs-at-risk (OARs) were also considered for reference. The non-parametric Anova (Friedman matched-pairs signed-rank test) was used for comparative analyses. <b>Results:</b> IMPT improved target coverage and dose homogeneity even if the skin was included into optimization strategy (HI<sub>IMPT2</sub> = 0.11 vs. HI<sub>IMXT</sub> = 0.22 and CI<sub>IMPT2</sub> = 0.96 vs. CI<sub>IMXT</sub> = 0.82, <i>p</i> &lt; .05). A significant relative skin risk reduction (RR = NTCP<sub>IMPT</sub>/NTCP<sub>IMXT</sub>) was obtained with IMPT<sub>2</sub> including the skin in the optimization with a RR reduction ranging from 0.3 to 0.9 depending on the analyzed skin toxicity endpoint/model. Both IMPT plans attained significant OARs dose sparing compared with IMXT. As expected, the heart and lung doses were significantly reduced using IMPT. Accordingly, IMPT always provided lower NTCP values. <b>Conclusions:</b> IMPT guarantees optimal target coverage, OARs sparing, and simultaneously minimizes the risk of skin morbidity. The applied model-based approach supports the potential clinical relevance of IMPT for left-side BC and RNI and might be relevant for the setup of cost-effectiveness evaluation strategies based on NTCP predictions, as well as for establishing patient selection criteria.