L. Pandey (Ambala, India)
Maharshi Markandeshwar Institute of Medical Sciences and ResearchAuthor Of 1 Presentation
84P - Prospective Comparative Study of Dosimetric Parameters and Acute Radiation Toxicity of 3-Dimensional Conformal Radiotherapy (3DCRT) And Volumetric Modulated Arc Therapy (VMAT) In Post Mastectomy Carcinoma Breast Patients
Abstract
Background
Radiation therapy (RT) is an integral component of breast cancer management. For mitigating the normal tissue toxicity, many radiotherapy techniques have been explored and utilized. In the present study, we compare post modified radical mastectomy (PMRM) radiotherapy plans utilizing 3DCRT and VMAT techniques.
Methods
This prospective, single-institutional study, includes 40 PMRM patients. For all the patient, both the plans were generated and dosimetric comparison was done. 20 patients were treated with the 3DCRT and the other half were with the VMAT. All the patients received 40Gy in 15 fractions over 3 weeks. Acute reactions were compared at end of RT, 6 weeks and 3 months.
Results
The planning target volume (PTV) receiving V95%, Homogeneity Index and Conformity Index were significantly better in VMAT than 3DCRT (p<0.001). V20, V30 and Dmean values of the ipsilateral lung (p<0.001) were significantly less in VMAT. In left-sided PMRM patients, V25 of the heart was significantly (p<0.001) lower in VMAT while in right-sided mastectomy there was a non-significant difference (p=0.13). In both left and right mastectomy patients, V5 of heart and both the lungs was significantly higher in VMAT (P<0.001). Mean dose of the oesophagus and contralateral breast were higher in VMAT (p<0.001). Both techniques were equivalent in terms of acute toxicity. Dosimetric parameters are shown in the below table.
Parameter 3DCRT VMAT PTV V95% (%) 83.84 ± 11.52 98.06 ± 1.10 Conformity Index (CI) 0.83 ± 0.11 0.97 ± 0.01 Homogeneity Index (HI) 0.173 ± 0.03 0.10 ± 0.01 V20 I/L lung (%) 46.49 ± 7.6 29.82 ± 2.5 V30 I/L lung (%) 36.51 ± 7.33 19.26 ± 2.4 V5 I/L lung (%) 62.29 ± 7.46 78.75 ± 12.62 V5 C/L lung (%) 2.24 ± 2.46 39.60 ± 20.8 Mean heart dose (Left MRM) (Gy) 13.02 ± 4.96 13.24 ± 2.39 V25 heart (Left MRM) (%) 26.17 ± 12.27 12.81 ± 4.18 V25 Heart (Right MRM) (%) 2.16 ± 3.35 1.23 ± 1.53 V5 heart (Left MRM) (%) 44.75 ± 17.32 87.49 ± 13.04 V5 heart (Right MRM) (%) 11.57 ± 11.66 66.79 ± 25.89 Dmax spinal cord (Gy) 34.45 ± 6.21 16.46 ± 6.30 Mean esophagus dose (Gy) 8.65 ± 2.9 11.3 ± 3.05 Mean contralateral breast (Gy) 2.59 ± 1.64 4.02 ± 1.01
Conclusions
VMAT provided better PTV coverage, reduced high dose volume to heart and I/L lung, more homogenous, and conformal plans, as compared to 3DCRT plans. VMAT will be helpful, where 3DCRT is not giving proper dose distribution due to variation in chest wall shape or is giving high heart or I/L lung doses. Consequences of higher low-dose volumes to normal tissues with VMAT need to be weighed against the benefits of reducing high-dose volumes on an individual patient basis.
Legal entity responsible for the study
Maharishi Markandeshwar Institute of Medical Sciences and Research.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.