Improving the Palliative Patient Journey in Radiation Oncology (original) (raw)

2019, International Journal of Radiation Oncology*Biology*Physics

Purpose/Objective(s): Radiotherapy (RT) has an important role in the symptomatic relief and improvement in the quality of life for patients with bony and soft tissue metastases. We hypothesised a streamlined palliative care pathway by removing the need for a simulation computed tomography (sCT) scan. The aim of this study was to investigate the use of the patient's diagnostic CT (dCT) dataset to produce palliative 3D conformal radiotherapy (3D-CRT) treatment plans. Materials/Methods: The impact on dose distribution of Hounsfield Units (HUs) variance from different dCT sources, patient position and couch curvature was assessed retrospectively. From 150 patients treated with palliative 3D-CRT, a sample of 92 diagnostic datasets covering the most common treatment sites were used. A slab geometry phantom was created in the treatment planning system to compare the dosimetric impact of variance in HU. Dosimetric evaluations were undertaken by comparing the clinical plan calculated with fixed monitor units on the dCT. The integration of dCT treatment planning into the palliative care path was done prospectively. Patients booked for palliative RT (1 to 5 fractions), and a dCT acquired within the last 4 weeks, were included. The dCT had to encompass the area of interest and have a complete field of view including body contours. Patients were then simulated as per standard department protocol, but in the dCT position. Treatment was dual planned on the dCT and the sCT and delivered with daily image guidance as per routine treatment. Results: The mean HU for vertebra (nZ12), femoral head (nZ17), lung (nZ22) and soft tissue (nZ41), was 185AE50, 416AE125,-741AE91, and 59AE41 respectively. From tissue slab phantoms, dose differences due to HU variation resulted in lung HU changes that impact dosimetry in the order of 3-5% for 6MV. In patient dCTs, uncertainty in dose calculation due to HU variation in the lung was in the order of 2.5-5% for 10MV and 1.5-3.5% for 18MV which needs to be considered when calculating on diagnostic scans since the higher the energy, the less impact change in HU has on dose. From the retrospective analysis, the most suitable treatment sites for the application of dCT planning were the abdomen, lumbar or thoracic spine, pelvis and sacrum. Of the first 35 patients planned and treated with dCT, 28 plans used 18MV, 6 plans 6MV and one plan 6/18MV mix. A curved full body vac-bag was designed to enable better replication of the posterior body curvature in dCTs for treatment. Dosimetric evaluations were made between the dCT and pre-treatment cone beam CT in 32 patients, with the planning target volume (PTV) dose difference being <2% in 29 patients. Conclusion: 3D-CRT plans for patients with bony and soft tissue metastases can be produced using dCT, eliminating the need for the sCT. This was demonstrated to be feasible and has been implemented as a standard clinical care pathway, with major implications for improving the care journey for patients with metastatic cancer.