DOSIMETRIC ANALYSIS OF INCIDENTALAXILLARY IRRADIATION IN BREAST CANCER USING TANGENTIAL FIELDS TREATED BY 3DCRT TECHNIQUE

Abstract

Introduction Radiotherapy is an important aspect of treatment for multimodality approach in cancer breast. Inclusion of axillary nodes in radiotherapy tangential elds remains a long-standing controversial issue. It is considered that axillary nodes receive incidental radiation through tangential beams of chest-wall. The benet of decreasing regional recurrences with axillary nodal irradiation needs to be weighed against the risk of chronic lymphedema and its impact on quality of life. The following study was done to analyze the incidental dose received to axillary region and whether the addition of radiotherapy to axillary region will be useful. Material and methods Twenty post Modied Radical Mastectomy (MRM) patients who had received adjuvant radiotherapy from 2018-2021were retrospectively selected. Planning was a done with Field in Field–Forward planned–3DCRT with mono-isocentric technique. Dose prescribed was 50Gy/25 fractions. Axillary Lymph nodes were contoured according to RTOG guidelines. Various parameters of PTV(V95,D90, D95, Dmax, Dmean, Homogeneity Index(HI), Conformity Index (CI), Volume of PTV), Axillary Lymph nodes I, II, III and SCF (Dmean,V95, V90, Volume) and BMI were evaluated. Correlation was done among these parameters and Statistical analysis was done using Pearson-Correlation coefcient. Results The mean dose to axillary Lymph node level I, II, III were 45.75Gy, 31.80Gy and 25.83Gy respectively. The V90% and V95% of Axillary level–III also received a dose of 32.97Gy and 22.73Gy respectively. The combined volume of I and II received a mean dose of 40.85Gy and all three levels received 39.44.Gy. There is a weak correlation of SCF dosimetry with axillary nodal volumes although PTV volumes and BMI had positive correlation with axillary lymph nodal irradiation. ConclusionAxillary levels I and II received substantial amount of incidental radiation by the tangential eld 3DCRT technique. Our small sample size may have impacted a more detailed analysis of the correlation among variables. However more prospective clinical studies addressing this issue may help in understanding the risks versus benets of axillary lymph nodal irradiation.