The goal of this randomized, phase III trial is to to determine if Spatially Fractionated Lattice Radiotherapy (SFRT) known as LATTICE therapy, leads to a greater reduction in pain or discomfort compared with conventional Radiation Therapy (RT) in patients with large tumours. This is evaluated by assessing if a greater proportion of patients who receive RT with SFRT will have an improvement in pain/discomfort at 30 days defined using the International Consensus Pain Response (ICPR) compared with those treated with conventional RT.

This study aims to compare the pain scores of patients receiving conventional radiotherapy and spatially fractionated lattice radiotherapy (SFRT). About half of all cancer patients will undergo palliative radiotherapy (RT) during their illness to manage distressing symptoms such as pain and bleeding. Great and more durable pain responses have been observed with higher dose RT, including stereotactic body radiation therapy (SBRT). Unfortunately, it is not possible to treat large tumors with SBRT for several reasons. SFRT is an innovative RT technique that addresses some of the limitations of SBRT. SFRT uses very high doses of radiation on specific spots inside the tumour, creating a lattice-like pattern. The outer edges of the tumor get a much lower dose, which helps protect nearby healthy organs from radiation. Early phase studies have shown excellent response rates in terms of pain as well as dramatic and rapid resolution of large tumours. Similar results with high responses and low toxicity have been reported in the setting of locally advanced and bulky lung cancer, head and neck cancer, and cervical cancer. This study determines if SFRT leads to a greater reduction in pain or discomfort compared with conventional radiation therapy (RT), defined using the International Consensus for Pain Response (ICPR) which includes the short form Brief Pain inventory questionnaire and self-reporting of opioid and/or co-analgesic use, measured at 30 +/- 7 days following treatment. Pain is defined by a worst pain score of 2 or greater at the target site on the short form Brief pain inventory, within 7 days prior to randomization. The primary endpoint of this study is improvement in pain response with secondary endpoints including treatment-related toxicity above grade 2, objective tumor response, survival, and health-economics endpoints.

Inclusion Criteria:

• Diagnosis of solid tumor by at least one criterion below:

  a. Pathologically or cytologically proven solid tumor greater than 5 cm (largest dimension) from a primary site or site of metastasis and unsuitable for surgical resection or definitive RT. b. HCC diagnosed by standard imaging criteria permitted: arterial enhancement and delayed washout on multiphasic computerized tomography (CT) or magnetic resonance imaging (MRI) in the setting of cirrhosis or chronic hepatitis B or C without cirrhosis

• Eastern Cooperative Oncology Group (ECOG) Status: 0-4 within 14 days of randomization

• In the investigator's opinion, patient requires palliative radiation therapy to a lesion >5 cm measured in one of the following ways:

• Imaging performed within 90 days prior to randomization per Response Evaluation Criteria in Solid Tumors (RECIST)

• CT simulation performed for radiation planning

• Able to understand and provide written consent

• Willing and have the ability to complete the baseline and post-treatment questionnaires (short form brief-pain inventory) and to maintain a pain diary

• Patient is not pregnant, planning on becoming pregnant or planning on fathering a child in the next 90 days

• Patient must be accessible for treatment and follow-up. Investigators must ensure the patients randomized on this trial will be available for complete documentation of the treatment, adverse events, and follow-up

Exclusion Criteria:

• Prior radiotherapy that would result in substantial overlap of the irradiated volume thus precluding per protocol treatment
• Requirement for urgent surgical intervention prior to radiation treatment
• Confirmed pregnancy
• Hematologic primary malignancy
• Medical condition precluding the delivery of per protocol treatment (e.g. connective tissue disorder)
• Tumors overlying critical CNS, heart or spinal cord compression