Abstract
Background: Conformal Radiotherapy techniques adapting to the ballistics of delineated volumes allowed significant reduction in excess radiation induced mortality however the increasing number of long-term survivors and expanding use of cardiotoxic drug highlight the persistent need for maximal cardiac possible sparing. The low dose volume of left ventricle are better predictor of acute coronary events than mean heart dose. Materials and Methods: 38 post-MRM patients were randomized to treatment by 3Dimensional Conformal Radiotherapy (3D CRT) and Intensity Modulated Radiotherapy (IMRT) technique. Two tangential beams were used in 3D CRT technique while five to seven (mostly tangential beams) were used in inversely planned IMRT technique. The dose volume parameters of planning target volume, heart and left ventricle were compared. Results: The dosimetry of Planning target volume showed significantly better coverage in IMRT technique (D90, D95) however the D50 was comparable in both the techniques. In dosimetry of heart, the high dose volumes (V30, V40) were nearly comparable in both the techniques. The other dose volume parameters (V5, V10, V20, V25, D33, D67, D100) and the mean dose were significantly lesser in 3D CRT technique along with significantly better sparing of left ventricle (Dmean and V5). Conclusion: The dosimetry of target volume was better with IMRT technique, but this was accompanied by a huge increase in dose to whole heart and specifically the left ventricle which has strong potential to translate into an increased cardiotoxicity. A better distribution of the target region may be obtained by multiple segmentation of the two tangential fields in 3D CRT plans with further reduction in dose to heart and left ventricle.
Highlights
Conformal Radiotherapy techniques adapting to the ballistics of delineated volumes allowed significant reduction in excess radiation induced mortality the increasing number of long-term survivors and expanding use of cardiotoxic drug highlight the persistent need for maximal cardiac possible sparing
The dosimetry of planning target volume (PTV) was better in Intensity Modulated Radiotherapy (IMRT) technique with a significantly higher observed mean value of D90 and D95 D50 was nearly comparable with no significant difference observed in both the techniques
The dose volume parameters, D95% and D90% showed significantly higher mean observed values in IMRT technique the D50% which is considered to be largely representative of dose distribution inside the entire PTV and a better estimate of optimal coverage than other dose volume parameters showed no significant difference in two techniques [13]
Summary
Conformal Radiotherapy techniques adapting to the ballistics of delineated volumes allowed significant reduction in excess radiation induced mortality the increasing number of long-term survivors and expanding use of cardiotoxic drug highlight the persistent need for maximal cardiac possible sparing. Conclusion: The dosimetry of target volume was better with IMRT technique, but this was accompanied by a huge increase in dose to whole heart and the left ventricle which has strong potential to translate into an increased cardiotoxicity. Due to improvements in diagnostic modalities, wide implementation of screening programmes [2], advances in multimodality treatment, long-term cause-specific survival for all stages has shown significant improvement over the past few decades [3,4]. This has prompted an increased focus on long term treatment related toxicities. Conformal radiotherapy techniques adapting to the ballistics and the energy to the delineated volumes with careful evaluation of the dose-volume distribution of critical organs allowed a drastic reduction in cardiac mortality
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