Frontiers in Oncology (Jan 2022)

Adaptive MR-Guided Stereotactic Radiotherapy is Beneficial for Ablative Treatment of Lung Tumors in High-Risk Locations

  • Sebastian Regnery,
  • Sebastian Regnery,
  • Sebastian Regnery,
  • Sebastian Regnery,
  • Sebastian Regnery,
  • Carolin Buchele,
  • Carolin Buchele,
  • Fabian Weykamp,
  • Fabian Weykamp,
  • Fabian Weykamp,
  • Fabian Weykamp,
  • Moritz Pohl,
  • Philipp Hoegen,
  • Philipp Hoegen,
  • Philipp Hoegen,
  • Philipp Hoegen,
  • Philipp Hoegen,
  • Tanja Eichkorn,
  • Tanja Eichkorn,
  • Tanja Eichkorn,
  • Tanja Eichkorn,
  • Thomas Held,
  • Thomas Held,
  • Thomas Held,
  • Thomas Held,
  • Jonas Ristau,
  • Jonas Ristau,
  • Jonas Ristau,
  • Carolin Rippke,
  • Carolin Rippke,
  • Laila König,
  • Laila König,
  • Laila König,
  • Laila König,
  • Michael Thomas,
  • Michael Thomas,
  • Michael Thomas,
  • Hauke Winter,
  • Hauke Winter,
  • Hauke Winter,
  • Sebastian Adeberg,
  • Sebastian Adeberg,
  • Sebastian Adeberg,
  • Sebastian Adeberg,
  • Sebastian Adeberg,
  • Jürgen Debus,
  • Jürgen Debus,
  • Jürgen Debus,
  • Jürgen Debus,
  • Jürgen Debus,
  • Sebastian Klüter,
  • Sebastian Klüter,
  • Juliane Hörner-Rieber,
  • Juliane Hörner-Rieber,
  • Juliane Hörner-Rieber,
  • Juliane Hörner-Rieber,
  • Juliane Hörner-Rieber

DOI
https://doi.org/10.3389/fonc.2021.757031
Journal volume & issue
Vol. 11

Abstract

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PurposeTo explore the benefit of adaptive magnetic resonance-guided stereotactic body radiotherapy (MRgSBRT) for treatment of lung tumors in different locations with a focus on ultracentral lung tumors (ULT).Patients & MethodsA prospective cohort of 21 patients with 23 primary and secondary lung tumors was analyzed. Tumors were located peripherally (N = 10), centrally (N = 2) and ultracentrally (N = 11, planning target volume (PTV) overlap with proximal bronchi, esophagus and/or pulmonary artery). All patients received MRgSBRT with gated dose delivery and risk-adapted fractionation. Before each fraction, the baseline plan was recalculated on the anatomy of the day (predicted plan). Plan adaptation was performed in 154/165 fractions (93.3%). Comparison of dose characteristics between predicted and adapted plans employed descriptive statistics and Bayesian linear multilevel models. The posterior distributions resulting from the Bayesian models are presented by the mean together with the corresponding 95% compatibility interval (CI).ResultsPlan adaptation decreased the proportion of fractions with violated planning objectives from 94% (predicted plans) to 17% (adapted plans). In most cases, inadequate PTV coverage was remedied (predicted: 86%, adapted: 13%), corresponding to a moderate increase of PTV coverage (mean +6.3%, 95% CI: [5.3–7.4%]) and biologically effective PTV doses (BED10) (BEDmin: +9.0 Gy [6.7–11.3 Gy], BEDmean: +1.4 Gy [0.8–2.1 Gy]). This benefit was smaller in larger tumors (−0.1%/10 cm³ PTV [−0.2 to −0.02%/10 cm³ PTV]) and ULT (−2.0% [−3.1 to −0.9%]). Occurrence of exceeded maximum doses inside the PTV (predicted: 21%, adapted: 4%) and violations of OAR constraints (predicted: 12%, adapted: 1%, OR: 0.14 [0.04–0.44]) was effectively reduced. OAR constraint violations almost exclusively occurred if the PTV had touched the corresponding OAR in the baseline plan (18/19, 95%).ConclusionAdaptive MRgSBRT is highly recommendable for ablative treatment of lung tumors whose PTV initially contacts a sensitive OAR, such as ULT. Here, plan adaptation protects the OAR while maintaining best-possible PTV coverage.

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