IMRT and carbon ion boost for malignant salivary gland tumors: interim analysis of the COSMIC trial.

Background: The COSMIC trial is designed to evaluate toxicity in dose-escalated treatment with intensity-modulated radiotherapy (IMRT) and carbon ion boost for malignant salivary gland tumors (MSGT) of the head and neck including patients with inoperable/ incompletely resected MSGTs (R2-group) and completely resected tumors plus involved margins or perineural spread (R1-group).

Methods: COSMIC is a prospective phase II trial of IMRT (25 × 2 Gy) and carbon ion boost (8 × 3 GyE). Primary endpoint is mucositis CTC°III, secondary endpoints are local control, progression-free survival, and toxicity. Evaluation of disease response is carried out according to the Response Evaluation Criteria in Solid Tumors (RECIST); toxicity is assessed using NCI CTC v 3.0.

Results: Twenty-nine patients were recruited from 07/2010 to 04/2011, all patients have at least completed first follow-up. Sixteen patients were treated in the R2-group, 13 in the R1-group. All treatments were completed as planned and well tolerated, mucositis CTC grade III was 25% (R2) and 15.4% (R1), no dysphagia CTC grade III was observed, no feeding tubes were necessary. Side-effects rapidly resolved, only 4 patients (13.8%) reported xerostomia grade II at first follow-up. Overall response rate (complete and partial response) according to RECIST in the R2-group is 68.8% at 6-8 weeks post treatment, all patients within this group showed radiological signs of treatment response.

Conclusion: No unexpected toxicity was observed, mucositis rates and other side effects do not differ between patients with visible residual tumor and macroscopically completely resected tumors. Initial treatment response is promising though longer follow-up is needed to assess local control.

Trial Registration: Clinical trial identifier NCT 01154270.