Novel Use of Continuous Positive Airway Pressure Permits Heart- and Lung-Sparing Mediastinal Involved-Site Radiation Therapy for Patient With Hodgkin Lymphoma in Community Clinic When Deep Inspiration Breath-Hold Technique Is Not Available

Continuous Positive Airway Pressure-Assisted Breathing With Supine Tangential Left Breast Radiation Therapy When Deep Inspiration Breath-Hold Radiation Therapy Was Ineffective or Unsuitable: Clinical Implications for an Affordable Heart-Sparing Breast Radiation Therapy to Reduce the Health Care Disparities in Low-Resource Settings

Purpose

To report continuous positive airway pressure (CPAP)-assisted breathing with supine tangential left breast radiation therapy (CPAP-RT) when deep inspiration breath-hold RT (DIBH-RT) was ineffective or unsuitable.

Methods and Materials

Ten patients with left breast cancer underwent computed tomography simulation scan (CT-sim) under DIBH followed by CPAP-assisted breathing (15 cm H2O) to create CPAP-RT plans in authors' institute. Reasons for CPAP-RT include inability to reproduce DIBH (n = 5), DIBH-RT plan exceeded dose limits to the heart (n = 2), and unable to proceed with planned DIBH-RT due to mechanical issues (n = 3). Radiation target volumes and organs at risk were contoured according to published atlas data. For dosimetric comparison, supine tangential fields for breast only RT (Breast-RT) and wide-tangential fields for breast + internal mammary nodal RT (Breast + IMN-RT) were used with prescription of 40 Gy in 15 fractions on each patients' CT-sim with free-breathing (FB), DIBH, and CPAP-assisted breathing, respectively.

Results

Planning target volume (PTV) coverage was acceptable and comparable in all RT plans. Compared with FB, both DIBH and CPAP-assisted breathing inflated the thorax and increased left lung volume on average by 46% and 51%, respectively (FB: 1230 vs DIBH: 1802 vs CPAP-assisted breathing:1860 cc, P < .01), and increased the shortest distance between PTVeval-Breast to the heart by 5.6 ± 3.0 and 11.9 ± 3.6 mm (P < .01) and to LAD by 4.9 ± 2.9 and 10.8 ± 4.3 mm, respectively (P < .01). Compared with FB, both DIBH and CPAP significantly reduced radiation dose to the heart and LAD. A mean dose to the heart (HeartDmean) was FB: 2.3 ± 0.9, DIBH: 1.2 ± 0.7, and CPAP: 0.9 ± 0.4 Gy in Breast-RT (P < .01); FB: 3.2 ± 1.7, DIBH: 1.7 ± 0.8, and CPAP: 1.3 ± 0.5 Gy in Breast + IMN-RT (P < .01). LADDmean was FB: 11 ± 4.5, DIBH: 5.4 ± 3.2, and CPAP: 2.4 ± 0.9 Gy in Breast-RT (P < .01); FB: 15.5 ± 7.8, DIBH: 7.4 ± 4.1, and CPAP: 3.5 ± 1.4 Gy in Breast + IMN-RT (P < .01). A maximum dose to LAD (LADDmax) was FB: 35.8 ± 8.7, DIBH: 22.4 ± 15.4, and CPAP: 7.8 ± 5.3 Gy in Breast-RT (P < .01); FB: 38.7 ± 5.0, DIBH: 25.3 ± 15.2, and CPAP: 10.2 ± 6.8 Gy in Breast + IMN-RT (P < .01). All patients successfully completed CPAP-RT.

Conclusions

CPAP-RT provides efficient and practical heart and LAD sparing RT using simple supine tangential fields for Breast-RT or wide-tangential fields for Breast + IMN-RT when DIBH-RT was ineffective or unsuitable. With its easy accessibility and low infrastructural requirement, CPAP-RT can provide affordable heart-sparing left breast RT to reduce the health care disparities in low-resource settings.

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

We aimed to determine the optimal pressure of continuous positive airway pressure (CPAP) for radiotherapy (RT) through changes in the dosimetric parameters and lung volume according to pressure. Patients with locally advanced lung cancer, who underwent CPAP during computed tomography (CT) simulation, were included. The air pressure was raised in five steps of 4, 7, 10, 14, and 17 cmH2O and a CT scan was performed at the baseline and at each pressure step, accompanied by contouring and RT planning. Paired t- and Wilcoxon signed rank tests were used to compare the volumetric and dosimetric parameters according to pressure and interpressure. A total of 29 patients were selected, and 158 CT datasets were obtained. The lung volume increased significantly at all pressures (p < 0.01). The Dmean of the lung decreased significantly from 7 cmH2O (p < 0.01), the V5, V10, V15, and V20 of the lung decreased significantly from 7 cmH2O with increasing pressure, and the Dmean and V5 of the heart decreased significantly from 14 cmH2O with increasing pressure. The V50 showed no significant differences at any pressure. We recommend the use of at least 7 cmH2O with 14 cmH2O as the optimal pressure to achieve the effect of heart preservation.

Application of Continuous Positive Airway Pressure for Thoracic Respiratory Motion Management: An Assessment in a Magnetic Resonance Imaging–Guided Radiation Therapy Environment

Purpose

Patient tolerability of magnetic resonance (MR)–guided radiation treatment delivery is limited by the need for repeated deep inspiratory breath holds (DIBHs). This volunteer study assessed the feasibility of continuous positive airway pressure (CPAP) with and without DIBH for respiratory motion management during radiation treatment with an MR-linear accelerator (MR-linac).

Methods and Materials

MR imaging safety was first addressed by placing the CPAP device in an MR-safe closet and configuring a tube circuit via waveguide to the magnet bore. Reproducibility and linearity of the final configuration were assessed. Six healthy volunteers underwent thoracic imaging in a 0.35T MR-linac, with one free breathing (FB) and 2 DIBH acquisitions being obtained at 5 pressures from 0 to 15 cm-H₂O. Lung and heart volumes and positions were recorded; repeatability was assessed by comparing 2 consecutive DIBH scans. Blinded reviewers graded images for motion artifact using a 3-point grading scale. Participants completed comfort and perception surveys before and after imaging sessions.

Results

Compared with FB alone, FB-10, FB-12, and FB-15 cm H₂O significantly increased lung volumes (+23%, +34%, +44%; all P <.05) and inferiorly displaced the heart (0.86 cm, 0.96 cm, 1.18 cm; all P < . 05). Lung volumes were significantly greater with DIBH-0 cm H₂O compared with FB-15 cm H₂O (+105% vs +44%, P = .01), and DIBH-15 cm H₂O yielded additional volume increase (+131% vs +105%, P = .01). Adding CPAP to DIBH decreased lung volume differences between consecutive breath holds (correlation coefficient 0.97 at 15 cm H₂O vs 0.00 at 0 cm H₂O). The addition of 15 cm H₂O CPAP reduced artifact scores (P = .03) compared with FB; all DIBH images (0-15 cm H₂O) had less artifact (P < .01).

Conclusions

This work demonstrates the feasibility of integrating CPAP in an MR-linac environment in healthy volunteers. Extending this work to a larger patient cohort is warranted to further establish the role of CPAP as an alternative and concurrent approach to DIBH in MR-guided radiation therapy.

Bilevel Positive Airway Pressure Ventilation for Improving Respiratory Reproducibility in Radiation Oncology: A Pilot Study

Background

Strategies for managing respiratory motion, specifically motion-encompassing methods, in radiation therapy typically assume reproducible breathing. In reality, respiratory motion variations occur and ultimately cause tumor motion variations, which can result in differences between the planned and delivered dose distributions. Therefore, breathing guidance techniques have been investigated to improve respiratory reproducibility. To our knowledge, bilevel positive airway pressure (BIPAP) ventilation assistance has not been previously investigated as a technique for improving respiratory reproducibility and is the focus of this work.

Methods and Materials

Ten patients undergoing radiation therapy treatment for cancers affected by respiratory motion (eg, lung and esophagus) participated in sessions in which their breathing was recorded during their course of treatment; these sessions occurred either before or after radiation treatments. Both unassisted free-breathing (FB) and BIPAP ventilation-assisted respiratory volume data were collected from each patient using spirometry. Patients used 2 different BIPAP ventilators (fixed BIPAP and flexible BIPAP), each configured to deliver the same volume of air per breath (ie, tidal volume). The flexible BIPAP ventilator permitted patient triggering (ie, it permitted patients to initiate each breath), and the fixed BIPAP did not. Intrasession and intersession metrics quantifying tidal volume variations were calculated and compared between the specific breathing platforms (FB or BIPAP). In addition, patient tolerance of both BIPAP ventilators was qualitatively assessed through verbal feedback.

Results

Both BIPAP ventilators were tolerated by patients, although the fixed BIPAP was not as well tolerated as the flexible BIPAP. Both BIPAP ventilators showed significant reductions (P < .05) in intrasession tidal volume variation compared with FB. However, only the fixed BIPAP significantly reduced the intersession tidal volume variation compared with FB.

Conclusions

Based on the established correlation between tidal volume and tumor motion, any reduction of the tidal volume variation could result in reduced tumor motion variation. Fixed BIPAP ventilation was found to be tolerated by patients and was shown to significantly reduce intrasession and intersession tidal volume variations compared with FB. Therefore, future investigation into the potential of fixed BIPAP ventilation is warranted to define the possible clinical benefits.

Practical Heart Sparing Breast Cancer Radiation Therapy Using Continuous Positive Airway Pressure (CPAP) in Resource-Limited Radiation Oncology Clinics

PURPOSE

The purpose of this study was to report experiences of practical heart sparing breast radiation therapy (RT) using continuous positive airway pressure (CPAP) in resource-limited radiation oncology clinics.

PATIENTS AND METHODS

Twelve patients underwent computed tomography-simulations with both free-breathing (FB) and CPAP under the individual maximum tolerable air pressure. For each patient, left-sided breast RT plans (9 with breast only, 3 with breast and regional nodal stations) with FB and CPAP were created using 3-dimensional conformal RT (supine tangential or wide tangential RT fields) according to RTOG 1304. For daily RT, patients started CPAP in the patients waiting area for 15 minutes before entering the treatment room and continued CPAP during RT. Treatment setup times between breast RT with and without CPAP were compared.

RESULTS

All patients tolerated CPAP well with 8 to 15 cm H2O of air pressure. Compared with FB, CPAP inflated the thorax and increased total lung volume by 35±16% (CPAP: 3136±751 vs. FB: 2354±657 cm, P<0.01); caudally displaced the heart by 1.8 cm (P<0.01); and decreased heart volume within tangential RT fields on computed tomography-simulation scans by 96±4% (1.4±2.5 vs. 21±17 cm, P=0.02) in all patients. Planning target volume coverage was acceptable in all RT plans. CPAP lowered mean dose (Dmean) to heart by 47±22% (2.5±1.5 vs. 5.4±3.3 Gy, P<0.01); heart volume receiving ≥25 Gy (V25) by 82±18% (2.2±2.6 vs. 9.1±7.1%, P<0.01); Dmean to left anterior descending coronary artery by 68±8% (4.7±1.9 vs. 14.8±3.3 Gy, P<0.01). CPAP decreased radiation dose to ipsilateral lung compared with FB: 9.1±5.8 versus 11.2±8 Gy (20% reduction, P=0.03) of Dmean; 15.7±12.5 vs. 20.5±17.5% (25% reduction, P=0.03) of V20. RT with CPAP did not increase treatment setup time compared with FB (week 1: 362±63 vs. 352±77 s; week 2 to 5: 217±13 vs. 201±14 s, all P>0.25).

CONCLUSION

Novel use of CPAP allowed efficient and practical heart sparing breast RT without increasing infrastructural requirements in resource-limited radiation oncology clinics.