Abstract
PurposeTo assess the dosimetric benefits of online MR-guided radiotherapy (MRgRT) for esophageal cancer patients and to assess how these benefits could be translated into a local boosting strategy to improve future outcomes. MethodsTwenty-nine patients were in-silico treated with both a MRgRT regimen and a conventional image guided radiotherapy (IGRT) regimen using dose warping techniques. Here, the inter and intrafractional changes that occur over the course of treatment (as derived from 5 MRI scans that were acquired weekly during treatment) were incorporated to assess the total accumulated dose for each regimen. ResultsA significant reduction in dose to the organs-at-risk (OARs) was observed for all dose–volume-histogram (DVH) parameters for the MRgRT regimen without concessions to target coverage compared to the IGRT regimen. The mean lung dose was reduced by 28%, from 7.9 to 5.7 Gy respectively and V20Gy of the lungs was reduced by 55% (6.3–2.8%). A reduction of 24% was seen in mean heart dose (14.8–11.2 Gy), while the V25Gy of the heart was decreased by 53% (14.3–6.7%) and the V40Gy of the heart was decreased by 69% (3.9–1.2%). In addition, MRgRT dose escalation regimens with a boost up to 66% of the prescription dose to the primary tumor yielded approximately the same dose levels to the OARs as from the conventional IGRT regimen. ConclusionThis study revealed that MRgRT for esophageal cancer has the potential to significantly reduce the dose to heart and lungs. In addition, online high precision targeting of the primary tumor opens new perspectives for local boosting strategies to improve outcome of the local management of this disease.
Highlights
To assess the dosimetric benefits of online MR-guided radiotherapy (MRgRT) for esophageal cancer patients and to assess how these benefits could be translated into a local boosting strategy to improve future outcomes
Patients with histologically confirmed esophageal cancer treated with neoadjuvant chemoradiotherapy between December 2015 and April 2018 were eligible for inclusion
A total of 32 patients with esophageal cancer were enrolled in this study before the start of neoadjuvant chemoradiotherapy
Summary
To assess the dosimetric benefits of online MR-guided radiotherapy (MRgRT) for esophageal cancer patients and to assess how these benefits could be translated into a local boosting strategy to improve future outcomes. MRgRT dose escalation regimens with a boost up to 66% of the prescription dose to the primary tumor yielded approximately the same dose levels to the OARs as from the conventional IGRT regimen. Recent studies have suggested an expansion of 7–12 mm in different directions, resulting in PTVs that are approximately three times the volume of CTVs [3,4,5,13] These large PTVs inherently result in large high and intermediate dose levels at nearby organs-at-risk (OARs) such as the lungs and heart. It could be argued that a total dose of 61.6 Gy is too low to establish an increase in local control and that the OAR dose is a limiting factor in further dose escalation
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