Dosimetric comparison of static intensity-modulated radiation therapy and volumetric modulated arc therapy in lymphoma patients received mediastinal radiation / 国际肿瘤学杂志

ABSTRACT

Objective To compare target dosimetric distribution and normal tissue radiation between different static intensity-modulated radiation therapy (IMRT)plans and volumetric modulated arc therapy (VMAT),and to identify the best IMRT plan for lymphoma patients needed mediastinal radiation. Methods A total of 11 patients with lymphoma who received first course radiotherapy in the mediastinal region after che-motherapy in Cancer Hospital & Shenzhen Hospital,Chinese Academy of Medical Sciences and Peking Union Medical College from March 2017 to January 2019 were included in the study. There were 8 males and 3 fe-males,2 patients were in Ann Arbor stage Ⅰ-Ⅱ,and 9 cases in Ⅲ-Ⅳ stage. There were 6 patients with Hodgkin lymphoma (HL)and 5 patients with non-Hodgkin lymphoma (NHL). Patients with HL and NHL were given prescript doses of 36 Gy and 50 Gy,respectively. Three plans were designed for each patientstatic 5F-IMRT,7F-IMRT and VMAT plan. The target dosimetric distribution,normal tissue radiation dose,and effi-ciency of each plan were evaluated. Results The mean conformity index (CI)and homogeneity index (HI) values of plan target volume (PTV)in 5F-IMRT,7F-IMRT,VMAT plan were 0. 64 ± 0. 06,0. 67 ± 0. 05, 0. 76 ± 0. 04 (F = 17. 045,P < 0. 001)and 1. 07 ± 0. 01,1. 07 ± 0. 01,1. 09 ± 0. 01 (F = 9. 258,P =0. 001),respectively. VMAT showed significantly better CI than two static IMRT plans (both P < 0. 001),but worse HI (both P < 0. 001). The lungs low dose irradiation volume (V (V 5 )and high dose irradiation volume 30 )in 5F-IMRT,7F-IMRT,VMAT plan were (43. 98 ± 7. 77)％,(42. 71 ± 4. 98)％,(55. 92 ± 8. 16)％(F = 8. 281,P = 0. 001)and (8. 19 ± 2. 97)％,(8. 25 ± 2. 87)％,(7. 53 ± 3. 16)％ (F = 0. 140,P =0. 870),respectively. The volume of low dose irradiation in lungs of VMAT plan was significantly higher than 5F-IMRT and 7F-IMRT plans (both P < 0. 001),while high dose volume was no significant difference. The left and right breast low dose irradiation volume (V 4 )in 5F-IMRT,7F-IMRT and VMAT plan were (24. 29 ± 8. 14)％,(23. 87 ± 7. 70)％,(80. 17 ± 22. 92)％ (F = 14. 505,P = 0. 005)and (22. 12 ± 13. 28)％, (21. 13 ± 13. 01)％,(81. 77 ± 20. 76)％ (F = 13. 938,P = 0. 006),respectively. VMAT showed signifi-cantly higher breast low dose irradiation volume than static IMRT plan (both P < 0. 05). The number of monitor units and treatment time in 5F-IMRT,7F-IMRT,VMAT plan were (1622 ± 281)MU,(1729 ± 286)MU, (411 ± 75)MU (F = 105. 277,P < 0. 001)and (6. 79 ± 0. 93)min,(7. 42 ± 0. 95)min,(4. 98 ± 0. 00)min (F = 29. 545,P < 0. 001),respectively. VMAT showed significantly less monitor units than static IMRT (both P < 0. 001)and shorter treatment time (both P < 0. 001). Conclusion For lymphoma patients who have the indication of mediastinal radiotherapy,VMAT is highly efficient and has no definite dose advan-tage,the static 5F-IMRT or 7F-IMRT plan has good conformal and uniform target area,and some organs at risk exposure is even lower.