This is a pragmatic trial with patients randomized between standard of care palliative thoracic radiation therapy (RT) vs. hypofractionated, dose-escalated, esophageal-sparing (HD-ES) intensity modulated radiation therapy (IMRT).

The investigators hypothesize that the use of advanced radiation planning techniques to optimize dose to esophagus will permit the safe delivery of a modestly dose-escalated five-fraction course of palliative radiation to intrathoracic malignancies. This approach aims to deliver higher biologically effective doses while improving toxicity when compared to conventional approaches with the goal of prolonging high-quality overall survival.

Inclusion Criteria:

• Intrathoracic tumour requiring palliative radiation, either for palliation of symptoms or prevention of progression that is expected to cause symptoms in the next 6 months (in the judgement of the enrolling investigator)
• Willingness and ability to provide informed consent
• Eastern Cooperative Oncology Group performance status 0-3
• Age 18 years or older
• Prior or planned systemic treatment (chemotherapy, immunotherapy, targeted agents) is permissible at the discretion of the treating medical oncologist
• Concurrent palliative radiotherapy to other metastatic sites is permissible at the discretion of the treating radiation oncologist.
• Life expectancy greater than 3 months

Exclusion Criteria:

• Prior thoracic radiotherapy which, in the opinion of the treating of radiation oncologist, precludes the delivery of further thoracic radiotherapy. If there has been prior thoracic radiotherapy, a composite of all RT plans must be created, and the dose constraints herein must still be met. An allowance for 10 percent repair is permitted if at least 12 months have passed between the prior radiotherapy and the trial protocol specified radiotherapy.
• Serious medical comorbidities which, in the opinion of the treating radiation oncologist, preclude the delivery of radiotherapy. This includes interstitial lung disease.
• Pregnant or lactating women
• Inability to attend the full course of radiotherapy or planned follow-up visits