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

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 present study, we compare post modified radical mastectomy (PMRM) plans utilizing 3DCRT VMAT techniques. This prospective, single-institutional includes 40 PMRM patients. all patient, both were generated dosimetric comparison was done. 20 patients treated with other half VMAT. All received 40Gy in 15 fractions over 3 weeks. Acute reactions compared at end RT, 6 weeks months. The planning target volume (PTV) receiving V95%, Homogeneity Index Conformity significantly better than (p<0.001). V20, V30 Dmean values ipsilateral lung (p<0.001) less left-sided patients, V25 heart lower while right-sided there a non-significant difference (p=0.13). left right V5 lungs higher (P<0.001). Mean dose oesophagus contralateral Both equivalent terms acute toxicity. Dosimetric parameters are shown below table.Table: 84PParameter3DCRTVMATPTV V95% (%)83.84 ± 11.5298.06 1.10Conformity (CI)0.83 0.110.97 0.01Homogeneity (HI)0.173 0.030.10 0.01V20 I/L (%)46.49 7.629.82 2.5V30 (%)36.51 7.3319.26 2.4V5 (%)62.29 7.4678.75 12.62V5 C/L (%)2.24 2.4639.60 20.8Mean (Left MRM) (Gy)13.02 4.9613.24 2.39V25 (%)26.17 12.2712.81 4.18V25 Heart (Right (%)2.16 3.351.23 1.53V5 (%)44.75 17.3287.49 13.04V5 (%)11.57 11.6666.79 25.89Dmax spinal cord (Gy)34.45 6.2116.46 6.30Mean esophagus (Gy)8.65 2.911.3 3.05Mean (Gy)2.59 1.644.02 1.01 Open table new tab provided PTV coverage, reduced high to lung, more homogenous, conformal plans, as plans. will be helpful, where not giving proper distribution due variation chest wall shape or doses. Consequences low-dose volumes tissues need weighed against benefits reducing high-dose on individual patient basis.