Re-irradiation has attracted attention as a potential therapy for recurrent head and neck tumors. However, carotid blowout syndrome (CBS) has become a serious complication of re-irradiation because of the associated life-threatening toxicity. Determining of the characteristics of CBS is important. We conducted a multi-institutional study.

Head and neck carcinoma patients (n=381) were treated with 484 re-irradiation sessions at 7 Japanese CyberKnife institutions between 2000 and 2010.

Of these, 32 (8.4%) developed CBS, which proved fatal that median survival time after CBS onset was 0.1 month, and the 1-year survival rate was 37.5%. The median duration between re-irradiation and CBS onset was 5 months (range, 0-69 months). Elder age, skin invasion, and necrosis/infection were identified as statistically significant risk factors after CBS by univariate analysis. The presence of skin invasion at the time of treatment found only in postoperative case, is identified as only statistically significant prognostic factor after CBS in multivariate analysis. The 1-year survival rate for the group without skin invasion was 42%, whereas no patient with skin invasion survived more than 4 months (0% at 1 year, p=0.0049).

Careful attention should be paid to the occurrence of CBS if the tumor is located adjacent to the carotid artery. The presence of skin invasion at CBS onset is ominous sign of lethal consequences.