Excluding lung tissue from the ptv during internal mammary irradiation. A safe technique for oar-sparing?

Kai J. Borm, Christopher Hofmann, Mathias Düsberg, Markus Oechsner, Hendrik Dapper, Michal Devecka, Stephanie E. Combs

Research output: Contribution to journalArticlepeer-review

Abstract

The current study aims to determine whether exclusion of lung tissue from planning treatment volume (PTV) is a valid organ at risk (OAR)-sparing technique during internal mammary irradiation (IMNI). Twenty patients with left-sided breast cancer undergoing adjuvant radiotherapy including IMNI after mastectomy or lumpectomy with daily ConeBeam CT (CBCT; median n = 28) were enrolled in the current study. The daily dose distribution of the patients was estimated by recalculating treatment plans on CBCT-scans based on a standard PTV (PTV margin: 5mm-STD) and a modified PTV, which excluded overlapping lung tissue (ExLung). Using 3D-deformable dose accumulation, the dose coverage in the target volume was estimated in dependence of the PTV-margins. The estimated delivered dose in the IMN-CTV was significantly lower for the ExLung PTV compared to the STD PTV: ExLung: V95%: 76.6 ± 22.9%; V90%: 89.6 ± 13.2%, STD: V95%: 95.6 ± 7.4%; V90%: 99.1 ± 2.7%. Daily CBCT imaging cannot sufficiently compensate the anatomic changes and intrafraction movement throughout the treatment. Therefore, to ensure adequate delivery of the prescribed dose to the IMN-CTV, exclusion of lung tissue from the PTV to spare the OARs is not recommended.

Original languageEnglish
Article number1951
JournalCancers
Volume13
Issue number8
DOIs
StatePublished - 2 Apr 2021
Externally publishedYes

Keywords

  • Breast cancer
  • IGRT
  • Internal mammary irradiation
  • Organ-sparing
  • Radiotherapy

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