Purpose: To evaluate the appropriate modality for treating locally recurrent lung cancer patients following SBRT, using single fraction stereotactic body radiation therapy (SBRT), single fraction proton therapy, and single fraction interstitial high-dose-rate (HDR) brachytherapy for retreatment.
Methods: Six patients with recurrence (local failure) after SBRT were planned and evaluated using three modalities for retreatment: linac-based SBRT (VMAT using Pinnacle, ver-16.2), proton therapy (Pinnacle, ver-16.2), and HDR brachytherapy (Oncentra, ver-4.5, Ir-192 isotope); all treatments were prescribed to 30Gy in one fraction. All the plans for retreatment were exported to MIM Maestro (ver-7.0) for generating dose composites of each trial with the initial CyberKnife SBRT dose of 60Gy. Various parameters of target coverage and dose to the organs at risk (OARs) were compared.
Results: Interstitial HDR and proton plans showed reduction in OARs’ doses, specifically for heart, spinal cord, and trachea, while achieving comparable dosimetric coverage to the target volume. The average cumulative mean lung dose for proton therapy and HDR brachytherapy reduced by 2.0% and 5.2%, respectively. Both proton therapy and HDR brachytherapy also presented large decrease in average cumulative mean heart dose, 38.4% and 41.1%, respectively, in comparison to SBRT. For proton therapy and HDR brachytherapy, the maximum (0.035cc) spinal cord dose reduced by 38.4% and 36.9%; trachea (4cc) dose reduced by 31.5% and 68.7%, respectively.
Conclusion: This study reveals the benefit of using proton or interstitial HDR brachytherapy to reduce dose to OARs, which potentially can reduce side effects after salvage radiotherapy. Although single fraction proton therapy is uncommon, the findings of the current study may provide the clinicians with options of treating recurrent lung cancer patients with single fraction HDR brachytherapy or equivalent fractionated proton therapy.
Not Applicable / None Entered.