Background: Synchronous chemo-radiotherapy is an alternative to cystectomy in patients with muscle invasive bladder cancer (MIBC). BC2001 trial reported improved local control in patients randomised to synchronous chemo-radiotherapy compared to radiotherapy alone (James, Hussain, Hall et al NEJM 2012). TUXEDO trial reports phase I trial results with additional weekly cetuximab (Cet) in combination with Mitomycin c (MMC), 5-Fluouracil (5-FU) and concurrent radiotherapy (RT). Methods: This two centre phase I trial recruited 7 patients with MIBC in Queen Elizabeth Hospital Birmingham and Clatterbridge Cancer Centre Liverpool to synchronous chemotherapy using Loading dose of Cet 400 mg/m2 followed by weekly Cet 250 mg/m2, continuous infusion 5-FU 500mg/m²/day during fractions 1-5 and 16-20 of RT and MMC12mg/m²on day 1 in combination with radical RT treatment 64 Gys in 32 fractions. The primary endpoint was to assess toxicity. Secondary end- points included 3 months pathological complete response, loco-regional disease-free survival and overall survival. Results: Median age of patients was 70 (range: 60-75) years, all were male, 6 had received prior neoadjuvant chemotherapy. Two patients had T2B, 3 T3A and 2 T3B disease, all had G3, TCC disease, 6 patients had neo-adjuvant chemotherapy. All 7 patients completed RT as planned except for 1 who withdrew from trial after 5 weeks of protocol treatment due to relocation. Median dose intensity for Cet and MMC was 97.6% and for 5-FU was 99.4%. Grade 3 toxicity to report was maculopapular rash in 3 patients. Grade 2 toxicities include UTI/ frequency/ nocturia / fatigue /constipation / hypokalemia/epistaxis/palmar-plantar reported in 3/1/1/1/1/1/1/2 cases respectively. Grade 2 maculo-papular rash was reported in 3 cases. All seven patients have achieved complete responses at 3 months cystoscopic assessment. Patients continue on surveillance as per TUXEDO trial protocol. Conclusions: Synchronous chemotherapy with Cet and 5FU/MMC concurrent with radical RT is safe to deliver. Complete response rates are encouraging and a phase II trial with added centres within UK is being launched. Clinical trial information: NOT KNOWN.