Feasibility of proton transmission-beam stereotactic ablative radiotherapy versus photon stereotactic ablative radiotherapy for lung tumors: a dosimetric and feasibility study.

Benjamin Mou,Chris J Beltran,Sean S Park,Keith M Furutani,Kenneth R Olivier,Eric Deutsch

doi:10.1371/journal.pone.0098621

Abstract

Stereotactic ablative radiotherapy is being increasingly adopted in the treatment of lung tumors. The use of proton beam therapy can further reduce dose to normal structures. However, uncertainty exists in proton-based treatment plans, including range uncertainties, large sensitivity to position uncertainty, and calculation of dose deposition in heterogeneous areas. This study investigated the feasibility of proton transmission beams, i.e. without the Bragg peak, to treat lung tumors with stereotactic ablative radiotherapy. We compared three representative treatment plans using proton transmission beams versus conformal static-gantry photon beams. It was found that proton treatment plans using transmission beams passing through the patient were feasible and demonstrated lower dose to normal structures and markedly reduced treatment times than photon plans. This is the first study to demonstrate the feasibility of proton-based stereotactic ablative radiotherapy planning for lung tumors using proton transmission beams alone. Further research using this novel approach for proton-based planning is warranted.

Highlights

Stereotactic ablative radiotherapy (SABR) plays an essential role in the treatment of patients with medically inoperable early stage lung cancer and oligometastasis
We report on the feasibility of proton transmissionbeam SABR (PT-SABR) for lung tumors which uses the transmission portion of a spot scanning proton beam, i.e. without the Bragg peak
PTSABR planning requires fewer beams than photons, and careful selection of optimal beam angles allows for minimal dose to adjacent normal tissues and tumor dose escalation which may translate to improved local control rates

Summary

Introduction

Stereotactic ablative radiotherapy (SABR) plays an essential role in the treatment of patients with medically inoperable early stage lung cancer and oligometastasis. The use of protons for lung SABR is emerging as an appealing treatment option because of its potential to deliver higher doses of conformal radiotherapy and spare normal tissues better than traditional photons [1,2,3,4]. This can be achieved because of the natural characteristics of proton beams that deposit its dose at depth with no exit dose, referred to as a Bragg peak. To the best of the authors’ knowledge, this is the first report on the use of this novel approach to plan SABR with protons without using the Bragg peak, which may have dosimetric advantages over photon treatments

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Results

Conclusion