Document Type : Original Article
radiation oncology departement national cancer institute
radiation oncology department national cancer institute cairo university
Biophysics Department, Faculty of Science, Cairo University, Egypt
Purpose of work
To study the best planning techniques for post operative breast radiotherapy either F-IMRT or I-IMRT and VMAT . Another strategy is to check the dosimetric difference between using 6 or 10 MV energies for both I-IMRT and VMAT .
Materials and Method: In the present study, four different inverse plans and one forward plan of randomly selected twenty left breast cancer patients were compared dosimetrically.Plans were done on Monaco (5.1) treatment planning system and data analyses were accomplished using one-way Anova test using IBM SPSS (20) data editor software.
Results: Inverse planning achieve superior target coverage over forward planning (p value =0.001 ,0.07) and conformity index (p value < 0.05) maintaining adequate homogeneity index (p value = 0.461, 0.138) . Left lung and heart high dose levels decreased using I-IMRT, VMAT ( p value <0.05) at the cost of increasing volume irradiated by low doses (p value < 0.05 ). For contralateral lung VMAT increased absorbed dose over F-IMRT ( p < 0.05) but I-IMRT showed non significant increase of V5 GY ( p value = 0.14) .For contralateral breast both I-IMRT and VMAT increased absorbed dose over F-IMRT (P < 0.05 ) .
Conclusion: It may be concluded that with inverse planning achieved better target coverage that increases tumor control . Inverse planning also achieved lower volume of high doses that reduces acute radiation effect and increased irradiated volume by low doses significantly that increases the probability of late radiation effect.