A hybrid conformal planning technique with solitary dynamic portal for postmastectomy radiotherapy with regional nodes

Abstract

Purpose:This study focuses on incorporation of a solitary dynamic portal (SDP) in conformal planning for postmastectomy radiotherapy (PMRT) with nodal regions with an intention to overcome the treatment planning limitations imposed by conventional techniques.Materials and Methods:Twenty-four patients who underwent surgical mastectomy followed by PMRT were included in this study. Initially, a treatment plan comprising tangential beams fitted to beam's-eye-view (BEV) of chest wall (CW) and a direct anterior field fitted to BEV of nodal region, both sharing a single isocenter was generated using Eclipse treatment planning system. Multiple field-in-fields with optimum beam weights (5% per field) were added primarily from the medial tangent, fitted to BEV of entire target volume, and finally converted into a dynamic portal. Dosimetric analysis for the treatment plans and fluence verification for the dynamic portals were performed.Results and Discussion:Conformal plans with SDP showed excellent dose coverage (V95%>95%), higher degree of tumor dose conformity (≤1.25) and homogeneity (≤0.12) without compromising the organ at risk sparing for PMRT with nodal region. Treatment plans with SDP considerably reduced the lower isodose spread to the ipsilateral lung, heart, and healthy tissue without affecting the dose homogeneity. Further, gamma evaluation showed more than 96% pixel pass rate for standard 3%/3 mm dose difference and distance-to-agreement criteria. Moreover, this plan offers less probability of “geometrical miss” at the highly irregular CW with regional nodal radiotherapy.Conclusion:Hybrid conformal plans with SDP would facilitate improved dose distribution and reduced uncertainty in delivery and promises to be a suitable treatment option for complex postmastectomy CW with regional nodal irradiation.

Dosimetric evaluation of 3 and/or 4 field radiation therapy of breast cancers: clinical experience

“…Adequate target coverage is associated with tumour control which leads to improve biochemical relapse-free survival, cancer progression-free survival and cancer-specific survival. Several studies [8][9][10][11][12][13][14][15][16]20,22,23,26,27,30 have reported similar PTV_eval coverage for breast cancer patients. Tanaka et al 16 investigated the FIF technique with lung blocks for breast radiotherapy and reported V 95% and V 100% of 93•2 and 62•7% for patients treated with the FB technique.…”

“…This is achieved using two tangential fields to treat the intact breast or chest-wall and an anterior and sometimes opposed posterior fields to treat the regional lymph nodes in the upper axillary and supraclavicular regions. 3,[19][20][21][22][23][24][25][26][27] There are several techniques used for breast radiation therapy including the use of wedges, field-in-field (FIF), hybrid technique (involving open and optimised fields), intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT). Several studies have reported that using IMRT, VMAT, FIF or the hybrid technique to treat the breast and regional lymph nodes have greater target coverage, reduced hotspots and reduced doses to the organs at risk (OAR) compared to conventional treatment with wedges.…”

“…Several studies have reported that using IMRT, VMAT, FIF or the hybrid technique to treat the breast and regional lymph nodes have greater target coverage, reduced hotspots and reduced doses to the organs at risk (OAR) compared to conventional treatment with wedges. 4,6,7,10,11,14,18,23,[27][28][29][30] Some studies 6,9,[12][13][14]16,17,21,26,31 that have evaluated and compared the dosimetric parameters of three-dimensional conformal radiation therapy using FIF technique have reported significant maximum dose and hotspots reduction, improved dose coverage and a more homogenous distribution within the target. Other studies 6,8,11,12,15,18,26,27 have also used the hybrid technique for breast radiotherapy and observed similar improved dose coverage, reduced hotspots in the target and less dose to the OARs.…”

“…4,6,7,10,11,14,18,23,[27][28][29][30] Some studies 6,9,[12][13][14]16,17,21,26,31 that have evaluated and compared the dosimetric parameters of three-dimensional conformal radiation therapy using FIF technique have reported significant maximum dose and hotspots reduction, improved dose coverage and a more homogenous distribution within the target. Other studies 6,8,11,12,15,18,26,27 have also used the hybrid technique for breast radiotherapy and observed similar improved dose coverage, reduced hotspots in the target and less dose to the OARs. The impact of respiratory motion during breast radiation therapy has also been investigated comparing free-breathing (FB) and deep inspiration breath hold (DIBH) techniques.…”