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

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.

Voluntary versus mechanically-induced deep inspiration breath-hold for left breast cancer: A randomized controlled trial

BACKGROUND AND PURPOSE

Deep inspiration breath-hold (DIBH) protects critical organs-at-risk (OARs) for adjuvant breast radiotherapy. Guidance systems e.g. surface guided radiation therapy (SGRT) improve the positional breast reproducibility and stability during DIBH. In parallel, OARs sparing with DIBH is enhanced through different techniques e.g. prone position, continuous positive airway pressure (CPAP). By inducing repeated DIBH with the same level of positive pressure, mechanically-assisted and non-invasive ventilation (MANIV) could potentially combine these DIBH optimizations.

MATERIALS AND METHODS

We conducted a randomized, open-label, multicenter and single-institution non-inferiority trial. Sixty-six patients eligible for adjuvant left whole-breast radiotherapy in supine position were equally assigned between mechanically-induced DIBH (MANIV-DIBH) and voluntary DIBH guided by SGRT (sDIBH). The co-primary endpoints were positional breast stability and reproducibility with a non-inferiority margin of 1 mm. Secondary endpoints were tolerance assessed daily via validated scales, treatment time, dose to OARs and their inter-fraction positional reproducibility.

RESULTS

Differences between both arms for positional breast reproducibility and stability occurred at a sub-millimetric level (p < 0.001 for non-inferiority). The left anterior descending artery near-max dose (14,6 ± 12,0 Gy vs. 7,7 ± 7,1 Gy, p = 0,018) and mean dose (5,0 ± 3,5 Gy vs. 3,0 ± 2,0 Gy, p = 0,009) were improved with MANIV-DIBH. The same applied for the V_5Gy of the left ventricle (2,4 ± 4,1 % vs. 0,8 ± 1,6 %, p = 0,001) as well as for the left lung V_20Gy (11,4 ± 2,8 % vs. 9,7 ± 2,7 %, p = 0,019) and V_30Gy (8,0 ± 2,6 % vs. 6,5 ± 2,3 %, p = 0,0018). Better heart's inter-fraction positional reproducibility was observed with MANIV-DIBH. Tolerance and treatment time were similar.

CONCLUSION

Mechanical ventilation provides the same target irradiation accuracy as with SGRT while better protecting and repositioning OARs.

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.

Continuous positive airway pressure with deep inspiration breath hold in left-sided breast radiation therapy

A dosimetric study to evaluate the use of continuous positive airway pressure (CPAP), with free-breathing (CPAP-FB) or with deep inspiration breath hold (DIBH-CPAP) an adjunct and alternative to DIBH to reduce heart and lung dose in the radiation therapy (RT) of breast cancer planned for left side RT with regional nodes and internal mammary. A retrospective analysis of 10 left-sided breast cancer patients whose heart or lung dose constraints were not met after RT planning based on FB or DIBH simulations and were referred for CPAP-based planning. All patients were simulated using FB, DIBH, CPAP-FB, and CPAP-DIBH. Treatment plans were calculated to cover the breast/chest wall and regional nodes using tangential field-in-field technique (FiF). Dose-volume parameters for heart, ipsilateral lung, and contralateral breast were compared using the Wilcoxon signed-rank test. For all RT plans, mean heart dose (Gy) was lower for treatment plans with CPAP: CPAP-FB (mean 3.4 vs 7.4, p = 0.001) and CPAP-DIBH (mean 2.5 vs 7.4, p = 0.006) compared to FB alone. CPAP-DIBH also significantly reduced MHD as compared to DIBH alone (mean 2.5 vs 4.3 Gy, p = 0.013). CPAP-DIBH significantly reduced mean lung dose as compared to both FB (mean 14.4 vs 20.1, p = 0.005) and DIBH alone (mean 14.4 vs 17.4, p = 0.007). Eight of 10 patients did not meet ipsilateral lung V20Gy dose constraints (≥35% of lung receiving 20 Gy) in either the free breathing or DIBH plans, whereas 8 out of 10 met lung V20Gy goal constraints (≤30% of lung receiving 20 Gy) in the CPAP-DIBH plans. Based on the outcomes of our study, CPAP could be a strategy for reducing lung and heart dose, both in patients not able to execute DIBH and as an adjunct in those not deriving sufficient dose reduction from DIBH alone.