ALT GIST: This phase II trial is testing imatinib (a type of chemotherapy) alone and in combination with the oral drug regorafenib as a first line treatment for advanced gastrointestinal stromal tumours (GIST)A Randomised Phase II Trial of Imatinib Alternating With Regorafenib Compared to Imatinib Alone for the First Line Treatment of Advanced Gastrointestinal Stromal Tumour (GIST)

Exclusion

• Concurrent GI illness which may prevent absorption of imatinib or regorafenib - please note that prior gastrectomy or bowel resection does not exclude patients from this study.
• Use of other investigational drugs within 4 weeks prior to enrolment.
• Known sensitivity to any of the study drugs, study drug classes, or excipients in the formulation.
• Participants receiving therapeutic doses of warfarin.
• Presence of brain metastases.
• The presence of PDGFR D842V mutation or other mutation known to cause imatinib resistance.
• Inability to swallow tablets.
• Arterial thrombotic or ischaemic events, such as cerebrovascular accident or pulmonary embolism within 6 months prior to randomisation; or major venous thrombotic events requiring use of an anticoagulant such as warfarin within 6 months prior to randomisation.
• Poorly controlled hypertension (systolic blood pressure > 140 mmHg or diastolic pressure > 90 mmHg despite optimal medical management).
• Major surgical procedure, open biopsy, or significant traumatic injury within 28 days prior to randomisation, or non healing wound, ulcer or fracture.
• Congestive cardiac failure (NYHA ≥ grade 2), unstable angina or new onset angina within the previous 3 months, or AMI within the previous 6 months. Cardiac arrhythmias requiring anti-arrhythmic therapy (beta blockers or digoxin are permitted).
• Haemorrhage or bleeding event ≥ Grade 3 according to CTCAE v4.0 within 4 weeks prior to randomisation.
• Ongoing infection of > Grade 2 according to CTCAE v4.0.
• Active hepatitis B or C or HIV, or chronic hepatitis B or C requiring treatment with antiviral therapy. Testing for these is not mandatory unless clinically indicated.
• Interstitial lung disease with ongoing signs and symptoms.
• Persistent proteinuria of ≥ Grade 3 (>3.5g/24 hours) according to CTCAE v4.0
• Other significant medical or psychiatric condition judged by the investigator to interfere with protocol requirements.
• Use of biological response modifiers such as granulocyte colony stimulating factor (G-CSF), within 3 weeks prior to randomisation.
• Patients taking strong cytochrome P (CYP) CYP3A4 inhibitors (eg clarithromycin, indinavir, itraconazole, ketoconazole, nefazodone, nelfinavir, posaconazole, ritonavir, saquinovir, telithromycin, voriconazole) or strong CYP3A4 inducers (eg carbamazepine, phenobarbitol, phenytoin, rifampicin, St John's wort).
• History of another malignancy within 5 years prior to registration. Patients with a past history of adequately treated carcinoma-in-situ, basal cell carcinoma of the skin, squamous cell carcinoma of the skin, or superficial transitional cell carcinoma of the bladder are eligible. Patients with a history of other malignancies are eligible if they have been continuously disease free for at least 5 years after definitive primary treatment.
• Pregnancy, lactation, or inadequate contraception. Women must be post menopausal, infertile, or use a reliable means of contraception. Women of childbearing potential must have a negative pregnancy test done within 7 days prior to registration. Women of childbearing potential and men must agree to use adequate contraception before entering the trial until at least 8 weeks after the last study drug administration.