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When metastatic spinal cord compression (MSCC)  is diagnosed, life expectancy is short and palliative radiotherapy (RT) aim to relieve pain and prevent further damage to spinal cord and nerve roots. When irradiating the cervical and thoracic spine, the pharynx and esophagus receives a significant dose, which can lead to dysphagia negatively impacting the patient’s performance status and quality of life.

Intensity modulated RT (IMRT) enables a reduction of dose to the esophagus by compromising dose to the vertebrae. The ESO-SPARE phase III trial randomizes patients with MSCC in the cervical- or thoracic spine to either esophagus sparing- or standard RT.  Strict esophagus constraints are set in the experimental arm to reduce toxicity to a minimum. This results in plans with underdosing of the anterior vertebrae. To assure that the trial constraints resulted in overall acceptable plans, we performed an in-study QA analysis of the achieved dosimetric parameters for the first 34 included patients.

The trial is planned to include 200 patients referred for palliative radiotherapy in any fractionation, for MSCC or spinal nerve root compression in the cervical or thoracic spine. Co-primary endpoints are patient reported  (PRO-CTAE) esophageal toxicity and preserved ability to walk. Secondary endpoints are change in other PRO-CTCAEs including pain, quality of life, reirradiation rate and overall survival. The trial is approved by the regional ethical committee and is awaiting Clinicaltrials.gov ID. Patients receives a trial diary for PRO-CTCAE and quality of lives assessments during the 9-week follow-up period. A fully electronic version of the trial diary is being developed. The affected vertebra(es) are delineated as a GTV and a 5 mm PTV margin is added. In both arms the esophagus (+ pharynx) is delineated. In the experimental arm an optimization volume (PTV- (esophagus+3mm) is created.  IMRT plans are created for all patients. PTV constraints are V_95% > 90% in both arms. There were no constrains to GTV. In the interventional arm, the constraint to the esophagus is prioritized over PTV coverage. In the standard arm esophagus is not used for optimization. Esophagus D_0.027cc differs between fractionations but all corresponds to an EQD2 of 8 Gy (α/β = 3 Gy). If an included patient was treated on several cervicothoracic targets in the same treatment session, one plan per isocenter were included for analysis. 

The study opened in May 2021 and by late October, 34 patients are included at two institutions. Two patients in the experimental arm had GTV V_95% < 80%. Figure 1 shows dose plans from the two arms. Treatment characteristics are listed in Table 1. 

Figure 1 - Dose plans examples 

Maximum dose to the esophagus was significantly lower in the interventional arm at the cost PTV as well as GTV coverage. A passus, that allows the treating physician to violate the esophagus constraint if GTV V_90% < 94%, is amended to the trial protocol.