First Results Of Costar: A Randomised Trial Of 3-Dimensional Conformal Radiotherapy (3dcrt) Vs Cochlea-Sparing Intensity Modulated Radiotherapy (Cs-Imrt) In Patients With Parotid Cancer.

6006Background: 30-50% of patients receiving post-operative RT for parotid cancer experience ipsilateral hearing loss. IMRT can reduce radiation dose to the cochlea. COSTAR (CRUK/08/004) investigated the role of IMRT in reducing hearing loss in these patients. Methods: Patients with histologically confirmed carcinoma of the parotid gland (pT1-4, pN0-3, M0) were randomized 1:1 to receive CT-planned 3DCRT or CS-IMRT. 60Gy (R0 resection) or 65Gy (R1-2) in 30 fractions were delivered over 6 weeks. Treatment allocation used minimisation, balancing for centre and planned RT dose. The primary endpoint was proportion of patients with hearing loss in the ipsilateral cochlea of ≥10dB measured by bone conduction at 4000Hz 12 months (m) after RT; compared between randomized groups by an exact test (α=0.05). Secondary endpoints (α=0.01) included hearing loss at 6m and 24m, vestibular function, acute and late toxicity, patient reported quality of life (including Glasgow Hearing Aid Benefit Profile (GHABP), time to tumo...