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Session Item

Poster discussion 25: Lung 2

Session Type: Poster discussions

Track: Clinical

Journey:

Second In-field course of stereotactic body radiotherapy for thoracic tumors: a multicentre analysis

Panagiotis Balermpas, Switzerland

Presentation Number: PD-0872

Abstract

Abstract Title:

Second In-field course of stereotactic body radiotherapy for thoracic tumors: a multicentre analysis

Authors:

Caroline John¹, Riccardo Dal Bello¹, Nicolaus Andratschke¹, Matthias Guckenberger¹, Judit Boda-Heggemann², Eleni Gkika³, Frederick Mantel⁴, Hanno M. Specht⁵, Carmen Stromberger⁶, Franz Zehentmayr⁷, Oliver Blanck⁸, Panagiotis Balermpas¹

¹Zurich University Hospital, Radiation Oncology, Zurich, Switzerland; ²Medical Faculty Mannheim, Heidelberg University, Radiation Oncology, Mannheim, Germany; ³University Medical Center Freiburg, Radiation Oncology, Freiburg, Germany; ⁴University Hospital Würzburg, Radiation Oncology, Würzburg, Germany; ⁵Clinic for Radiation Oncology Freising, Radiation Oncology, Freising, Germany; ⁶Charite – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Radiation Oncology, Berlin, Germany; ⁷Paracelsus Medical University, Radiation Oncology, Salzburg, Austria; ⁸University Medical Center Schleswig-Holstein, Radiation Oncology, Kiel, Germany

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Purpose or Objective

Data of in-field thoracic re-irradiation with two courses of stereotactic radiotherapy (SBRT) is scarce. Aim of this study is to investigate patterns of care, efficacy and safety and to analyze cumulative dose distributions.

Material and Methods

Patients with a second SBRT-course in the lung, planning target volume (PTV) overlap and available treatment plans were analyzed in this retrospective, multicenter study. All plans and clinical data were centrally collected. Radiotherapy plans were subjected to summation and dosimetric evaluation (figures 1 and 2). All dosimetric and volumetric parameters were extracted using the software MIM (version 6.9.2, MIM Software Inc., Cleveland, USA). The applied dose was converted to the corresponding 2 Gy equivalent dose (EQD2) distribution using the parameters alpha/beta = 10 Gy (EQD2/10) for the tumor and alpha/beta = 3 Gy (EQD2/3) for the surrounding normal tissue. Kaplan-Meier curves were used for calculation of overall survival (OS), local and distant control rates (LCR, DCR).

Figure 1

Results

Twenty-seven patients from 8 centers have been amenable for evaluation: 12 with non-small-cell lung cancer, 16 with metastatic lesions. In 17 of the cases, the re-irradiated lesion was the only detectable tumor. The median PTV of the first and second SBRT was 35 cm³ and 29.5 cm³, respectively. The median PTV overlap was 22 cm³ and the median cumulative maximal EQD2/10 ponit-dose was 270.04 Gy. The median dose applied in the first SBRT course was 38.5 Gy to the 65%-isodose over a median of 5 fractions. 40 Gy in 5 fractions was the median prescription for the second SBRT-course. After a median interval of 20.2 months between the two SBRT-courses, the 1-year OS, -LCR and -DCR were 78.3%, 70.3% and 73.8% respectively. Three patients developed grade 1 and one patient grade 2 pneumonitis. No grade >2 toxicity was observed. A higher than median dose to the PTV in the second treatment correlated with improved OS (p = 0.005) and LCR (p = 0.055) and peripheral tumor location had also a significantly positive influence on local control (p = 0.013).

Conclusion

A second in-field course of SBRT with PTV overlap appears to be safe and achieves reasonable tumor control rates. A higher re-irradiation dose to the PTV is the most important factor for long-time tumor control and survival.