Room: AAPM ePoster Library
Purpose: Continuous positive airway pressure (CPAP) has recently shown promising results in radiotherapy. Our study evaluates the clinical worth of CPAP in SABR treatments for centrally located lung tumours. We present the effect of CPAP on tumour displacement to critical structures and plan dosimetry as well as patient tolerability.
Methods: Ten patients with centrally located lung tumours were enrolled in this ethics approved trial. Each patient underwent double CT simulation; free-breathing and with CPAP (15cm H20 pressure). 3DCRT plans were generated for both datasets with a 60Gy/8 fraction prescription. The treating clinician compared plan dosimetry and the patient underwent treatment with CPAP if deemed superior. Standard departmental imaging, immobilisation, planning, and clinical evaluation procedures were used. Patients ranked their CPAP experience from 1 (very good) to 10 (very bad). The minimum 3D tumour displacements to critical structures were evaluated retrospectively.
Results: CPAP provided superior overall plan dosimetry in seven patients, all of which successfully completed treatment delivery with CPAP. Tumour displacement to critical structures was increased with CPAP compared to free-breathing; on average the heart was further displaced by 3.8mm, oesophagus 0.9mm, proximal bronchus 3.6mm, spinal canal 8.2mm, ribs 2.3mm, great vessels 2.2mm, and trachea 2.3mm. Maximum doses to the heart, proximal bronchus, ribs, and great vessels were on average reduced with CPAP by 7.0Gy, 1.7Gy, 4.9Gy, and 2.9Gy respectively with no compromise to PTV dose coverage. Maximum doses to the oesophagus, spinal canal and trachea were on average increased with CPAP by 3Gy, 1Gy, and 2Gy respectively. The average CPAP ITV was 6% smaller than the free-breathing ITV. Patients tolerated CPAP extremely well, on average scoring CPAP tolerability 1.8, pressure comfort 2.2, and mask comfort 2.1.
Conclusion: CPAP displaced centrally located lung tumours further away from critical structures, improved overall dosimetry in 70% of patients, and was well tolerated.
Funding Support, Disclosures, and Conflict of Interest: This work received funding from Auckland City Hospital A+ Trust.