The Dosimetric and Temporal Effects of Respiratory-Gated, High-Dose-Rate Radiation Therapy in Patients With Lung Cancer

Abstract

Purpose:To evaluate the dosimetric and temporal effects of high-dose-rate respiratory-gated radiation therapy in patients with lung cancer.Methods:Treatment plans from 5 patients with lung cancer (3 nongated and 2 gated at 80EX-80IN) were retrospectively evaluated. Prescription dose for these patients varied from 8 to 18 Gy/fraction with 3 to 5 treatment fractions. Using the same treatment planning criteria, 4 new treatment plans, corresponding to 4 gating windows (20EX-20IN, 40EX-40IN, 60EX-60IN, and 80EX-80IN), were generated for each patient. Mean tumor dose, mean lung dose, and lung V20 were used to assess the dosimetric effects. A MATLAB algorithm was developed to compute treatment time.Results:Mean lung dose and lung V20 were on average reduced between −16.1% to −6.0% and −20.0% to −7.2%, respectively, for gated plans when compared to the corresponding nongated plans, and between −5.8% to −4.2% and −7.0% to −5.4%, respectively, for plans with smaller gating windows when compared to the corresponding plans gated at 80EX-80IN. Treatment delivery times of gated plans using high-dose rate were reduced on average between −19.7% (−0.10 min/100 MU) and −27.2% (−0.13 min/100 MU) for original nongated plans and −15.6% (−0.15 min/100 MU) and −20.3% (−0.19 min/100 MU) for original 80EX-80IN-gated plans.Conclusion:Respiratory-gated radiation therapy in patients with lung cancer can reduce lung dose while maintaining tumor dose. Because treatment delivery during gated therapy is discontinuous, total treatment time may be prolonged. However, this increase in treatment time can be offset by increasing the dose delivery rate. Estimation of treatment time may be helpful in selecting patients for respiratory gating and choosing appropriate gating windows.

Potential Morbidity Reduction for Lung Stereotactic Body Radiation Therapy Using Respiratory Gating

“…Furthermore, the fixed prescription scheme might limit the potential effect of gating that might be reached for specific patients and other dose regimes. The general trend of dose reduction by gating has been shown before [25,28,35]. Prunaretty et al showed a reduction of V20Gy by 33% [25].…”

“…Prunaretty et al showed a reduction of V20Gy by 33% [25]. Rouabhi et al [28] reported a reduction of the mean lung dose between 16.1% and 6.0% and of V20Gy between 20.0% to 7.2%. However, the clinical benefit of gating was questioned by others, who found only small dosimetric impact by gating [37,38] and thus concluded gating to be a solution only for a well-selected group of patients [25].…”

“…However, the performance of gating relies on the reproducibility of the breathing cycle and the extent of tumor motion. Another drawback of gating is the increased treatment time [26][27][28] depending on the duty cycle. Although in principle advantageous for all patients, one may expect gating to be especially beneficial in patients with critical scenarios such as central tumors or potentially increased toxicity risk in combination with systemic medication.…”

Efficacy and Optimal Pressure of Continuous Positive Airway Pressure in Intensity-Modulated Radiotherapy for Locally Advanced Lung Cancer

“…RGRT is a method of irradiating only a specific respiratory window, so the target volume can be reduced compared to free breathing [ 16 ]. Rouabhi et al reported that RGRT could reduce the mean lung dose and V20 by 6–16% and 7–20%, respectively, compared to the non-gated plans [ 17 ]. However, this method requires patient collaboration and a regular breathing pattern.…”

Impact of high-dose rate radiotherapy on B and natural killer (NK) cell polarization in peripheral blood mononuclear cells (PBMCs) via inducing non-small cell lung cancer (NSCLC)-derived exosomes

“…In addition, accumulated evidence indicates that stereotactic body radiotherapy is necessary to stimulating a systemic antitumor immune response (6,7). In recent years, ultrahigh-dose rate stereotactic body radiotherapy has become a focal point of research in the field of NSCLC radiotherapy, as this approach has the advantage of being able to deliver a high dose in a short period of time (8,9). However, whether or not ultrahigh-dose rate stereotactic body radiotherapy can augment the antitumor immune response is unknown, while the function of the dose rate in the regulation of the antitumor immune response is also poorly understood.…”