I-FIRST: This phase II trial will use Dabrafenib and/or Trametinib to enhance treatment for people with thyroid cancer who no longer respond to radioactive iodine (a standard treatment for people with this type of cancer)A Prospective, Multi-Centre Trial of TKI Redifferentiation Therapy in Patients With RAIR Thyroid Cancer (I-FIRST Study)

Summary

This is a non-randomised, open-label study for adults with radioiodine refractory differentiated thyroid cancer with BRAF V600E or NRAS mutations. Prior to commencing interventional treatment, participants will commence a low iodine diet and undergo thyroxine withdrawal and commence T3 replacement from day -27. On day -5 they will receive an oral dose of 124I (40MBq/1.08 mCi) with imaging at 24 hours (+/-6) post dose and a second imaging assessment within 120 hours. During Days 1-30, participants with BRAF V600E mutations will then receive Dabrafenib (oral, 150mg twice daily) and Trametinib (oral, 2mg once daily); and participants with RAS mutations will receive Trametinib (oral, 2mg once daily). All participants will then receive a second oral dose of I124 will be administered at day 24 followed by imaging at the same interval as baseline. Participants achieving >20Gy tumour uptake of I124 will be administered 6GBq (3.3Gy/GBq) 131I, I131 wb scan and SPECT/CT will be performed within 24 hours and at hospital discharge. Participants who do not achieve >20Gy tumour update of I-124 will move into follow up. Follow up will occur every 12 weeks for 12 months.