What is the clinical evidence from this study?

Study design: Observational. Population: Lung and oesophageal cancer with left-sided subclavicular pacemakers (n=80). Intervention: Helical tomotherapy vs. IMRT and VMAT. Primary outcome: Mean maximum dose (Dmax) to the CIED (p=<0.01).

What question did this study set out to answer?

This research aimed to compare the dosimetric outcomes of IMRT, VMAT, and helical tomotherapy for patients with cardiac implantable electronic devices undergoing thoracic radiotherapy.

June 14, 2026Journal of the Egyptian National Cancer Institute0 citationsOpen Access

Minimising pacemaker exposure in thoracic radiotherapy: a comparative study of IMRT, VMAT, and helical tomotherapy

Q: What are the key findings of this study?

Helical tomotherapy with a 1 cm field width significantly reduced the mean maximum dose to the pacemaker to 1.10 Gy compared to 1.86 Gy with IMRT and 1.68 Gy with VMAT (p < 0.01).

Q: What question did this study set out to answer?

This research aimed to compare the dosimetric outcomes of IMRT, VMAT, and helical tomotherapy for patients with cardiac implantable electronic devices undergoing thoracic radiotherapy.

SSSandeep SinghAmrita Vishwa Vidyapeetham SSSupratik SenBhubaneswar Borooah Cancer Institute ASAbhay Kumar SinghBLK Super Speciality Hospital

Key Result

Helical tomotherapy with a 1 cm field width significantly reduced the mean maximum dose to the pacemaker to 1.10 Gy compared to 1.86 Gy with IMRT and 1.68 Gy with VMAT (p < 0.01).

Key Points

This research aimed to compare the dosimetric outcomes of IMRT, VMAT, and helical tomotherapy for patients with cardiac implantable electronic devices undergoing thoracic radiotherapy.
Planned treatment for 80 patients with left-sided subclavicular pacemakers using IMRT, VMAT, and tomotherapy with varying field widths.
Parameters assessed included CIED doses, target coverage, organ-at-risk metrics, and delivery efficiency across techniques.
Statistical analysis was performed using repeated-measures ANOVA with Holm-Bonferroni correction.
Helical tomotherapy significantly reduced CIED dose, with mean Dmax at 1.10 ± 0.25 Gy compared to 1.86 ± 0.43 Gy (IMRT) and 1.68 ± 0.38 Gy (VMAT), p < 0.01.
Mean heart dose decreased from 8.2 Gy to 3.8 Gy, and mean lung dose from 9.4 Gy to 7.6 Gy with tomotherapy.
VMAT demonstrated superior delivery efficiency, requiring fewer monitor units and shorter beam-on time than IMRT.

Study Design

Type

Observational (n=80)

Multicenter

Structured PICO

Does helical tomotherapy reduce CIED dose compared to IMRT and VMAT in thoracic cancer patients with pacemakers?

Population

80 patients with lung and oesophageal cancer and left-sided subclavicular pacemakers undergoing comparative dosimetric evaluation of thoracic radiotherapy techniques.

Intervention

Helical tomotherapy (1 cm, 2.5 cm, and 5 cm field widths) using 6 MV FFF photons.

Comparator

IMRT and VMAT using 6 MV FFF photons.

Outcome

CIED dose endpoints including Dmax, D0.03 cc, and Dmean.surrogate

Helical tomotherapy significantly reduces pacemaker radiation dose compared to IMRT and VMAT in thoracic radiotherapy, though VMAT offers superior delivery efficiency.

Main Result

Absolute Event Rate: 1.1% vs 1.86%

p-value: p=<0.01

Limitations

Retrospective design and modest sample size
Dosimetric assessment was based on treatment planning data and phantom validation without patient-specific in-vivo dosimetry
Use of a single tomotherapy unit and C-arm LINAC model limits generalizability
Biological risk modelling was not incorporated
Evaluated pacemakers were positioned outside the primary beam, so findings apply only to non-overlap geometries
IMRT and VMAT beam arrangements did not systematically exclude beam exit through the device region
All tomotherapy plans used fixed pitch and modulation factor settings across field widths

Abstract

Abstract Purpose Patients with cardiac implantable electronic devices (CIEDs) increasingly require thoracic radiotherapy, but comparative evidence guiding technique selection remains limited. This study evaluated CIED dose, target coverage, organ-at-risk (OAR) sparing, and delivery efficiency across IMRT, VMAT, and helical tomotherapy in matched thoracic cases. Methods Eighty patients with left-sided subclavicular pacemakers were planned using five techniques: IMRT, VMAT, and tomotherapy with 1 cm, 2.5 cm, and 5 cm field widths. All plans used 6 MV FFF photons with harmonised dose constraints. CIED endpoints included Dmax, D0.03 cc, and Dmean. Secondary endpoints included PTV coverage, homogeneity, conformity, lung and heart dose metrics, monitor units, and beam-on time. Statistical comparisons were performed using repeated-measures ANOVA with Holm-Bonferroni correction.Out-of-field dose was validated using OSLDs in a RANDO phantom. Results Target coverage was comparable across techniques (PTV D95 ≈ 98.5–99.2%). CIED dose was significantly reduced with tomotherapy, with mean Dmax decreasing from 1.86 ± 0.43 Gy (IMRT) and 1.68 ± 0.38 Gy (VMAT)to 1.10 ± 0.25 Gy for the 1 cm field width ( p < 0.01). Mean heart dose decreased from 8.2 Gy to 3.8 Gy, and mean lung dose from 9.4 Gy to 7.6 Gy. VMAT required fewer monitor units (500 vs. 910 for IMRT) and shorter delivery (1–1.5 min), whereas tomotherapy ranged from 140 to 500 s. Conclusion Helical tomotherapy improves CIED sparing and selected OAR metrics while maintaining target coverage. However, VMAT offers superior delivery efficiency. Technique selection should therefore be individualised, balancing dosimetric benefit against intrafraction motion risk, target geometry, and patient-specific clinical priorities.

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