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. 2024 Apr 17;16(8):1534.
doi: 10.3390/cancers16081534.

A Prospective Study on Deep Inspiration Breath Hold Thoracic Radiation Therapy Guided by Bronchoscopically Implanted Electromagnetic Transponders

Yuzhong Jeff Meng  1 , Nikhil P Mankuzhy  1 , Mohit Chawla  2 , Robert P Lee  2 , Ellen D Yorke  3 , Zhigang Zhang  4 , Emily Gelb  1 , Seng Boh Lim  3 , John J Cuaron  1 , Abraham J Wu  1 , Charles B Simone 2nd  1   5 , Daphna Y Gelblum  1 , Dale Michael Lovelock  3 , Wendy Harris  3 , Andreas Rimner  1   6
Affiliations

A Prospective Study on Deep Inspiration Breath Hold Thoracic Radiation Therapy Guided by Bronchoscopically Implanted Electromagnetic Transponders

Yuzhong Jeff Meng et al. Cancers (Basel). .

Abstract

Background: Electromagnetic transponders bronchoscopically implanted near the tumor can be used to monitor deep inspiration breath hold (DIBH) for thoracic radiation therapy (RT). The feasibility and safety of this approach require further study.

Methods: We enrolled patients with primary lung cancer or lung metastases. Three transponders were implanted near the tumor, followed by simulation with DIBH, free breathing, and 4D-CT as backup. The initial gating window for treatment was ±5 mm; in a second cohort, the window was incrementally reduced to determine the smallest feasible gating window. The primary endpoint was feasibility, defined as completion of RT using transponder-guided DIBH. Patients were followed for assessment of transponder- and RT-related toxicity.

Results: We enrolled 48 patients (35 with primary lung cancer and 13 with lung metastases). The median distance of transponders to tumor was 1.6 cm (IQR 0.6-2.8 cm). RT delivery ranged from 3 to 35 fractions. Transponder-guided DIBH was feasible in all but two patients (96% feasible), where it failed because the distance between the transponders and the antenna was >19 cm. Among the remaining 46 patients, 6 were treated prone to keep the transponders within 19 cm of the antenna, and 40 were treated supine. The smallest feasible gating window was identified as ±3 mm. Thirty-nine (85%) patients completed one year of follow-up. Toxicities at least possibly related to transponders or the implantation procedure were grade 2 in six patients (six incidences, cough and hemoptysis), grade 3 in three patients (five incidences, cough, dyspnea, pneumonia, and supraventricular tachycardia), and grade 4 pneumonia in one patient (occurring a few days after implantation but recovered fully and completed RT). Toxicities at least possibly related to RT were grade 2 in 18 patients (41 incidences, most commonly cough, fatigue, and pneumonitis) and grade 3 in four patients (seven incidences, most commonly pneumonia), and no patients had grade 4 or higher toxicity.

Conclusions: Bronchoscopically implanted electromagnetic transponder-guided DIBH lung RT is feasible and safe, allowing for precise tumor targeting and reduced normal tissue exposure. Transponder-antenna distance was the most common challenge due to a limited antenna range, which could sometimes be circumvented by prone positioning.

Keywords: deep inspiration breath hold (DIBH); electromagnetic transponder (EMT); thoracic radiation therapy.

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Conflict of interest statement

Mohit Chawla: Honoraria from Intuitive Surgical as Medical Advisory Board member. Seng Boh Lim: research grant from IBA dosimetry. Abraham J. Wu: research grants from CivaTech Oncology; SAB member for Simphotek, Inc.; consulting fees from Nanovi A/S. Charles B. Simone II: Varian Medical Systems research grants and honorarium. Daphna Y. Gelblum: funding for institutional PI for Merck. Andreas Rimner: research grants from Varian Medical Systems, AstraZeneca, Merck, Pfizer, and Boehringer Ingelheim; consulting fees from AstraZeneca and Merck; and a Scientific Advisory Board Member for Merck. This investigator-initiated study was funded by Varian Medical Systems, Palo Alto, CA, USA, who provided the electromagnetic transponders for this study. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Distances of transponders from the gross tumor volume (GTV). (a) As an example, two of the three transponders implanted are seen in this axial slice from the simulation CT, at 1.66 cm and 2.79 cm from the surface of the GTV (cyan), respectively. (b) Histogram of distances from transponders to GTV.
Figure 2
Figure 2
Mean duty cycles (percentage of beam-on time over total treatment time) over all treatment fractions for patients treated with initial gating windows of ±2, 3, 4, or 5 mm.
Figure 3
Figure 3
Histograms of the percentage reductions in (a) planning target volume (PTV) and (b) mean dose to lung (excluding GTV), comparing DIBH to 4D-CT plans for each patient. In two patients, the DIBH plan had a slightly larger PTV than the 4D-CT plan; in a separate patient, the DIBH plan had a slightly higher mean lung (excluding GTV) dose than the 4D-CT plan; these cases are represented by negative values on the x-axis.
Figure 3
Figure 3
Histograms of the percentage reductions in (a) planning target volume (PTV) and (b) mean dose to lung (excluding GTV), comparing DIBH to 4D-CT plans for each patient. In two patients, the DIBH plan had a slightly larger PTV than the 4D-CT plan; in a separate patient, the DIBH plan had a slightly higher mean lung (excluding GTV) dose than the 4D-CT plan; these cases are represented by negative values on the x-axis.
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