Frequency, outcome and prognostic factors of carotid blowout syndrome after hypofractionated re-irradiation of head and neck cancer using CyberKnife: a multi-institutional study.

PURPOSE: 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. METHODS AND PATIENTS: Head and neck carcinoma patients (n=381) were treated with 484 re-irradiation sessions at 7 Japanese CyberKnife institutions between 2000 and 2010. RESULTS: 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). CONCLUSIONS: 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.

Comparison of calculated dose by helical tomotherapy treatment planning machine and measured dose of radiophotoluminescence glass dosimeter in lung lesions using Rando Phantom.

AIM: To examine the compatibility of the measured and calculated dose for the treatment of lung lesions by helical tomotherapy. MATERIALS AND METHODS: The administered dose was measured a total of 55 times at 22 points with a radiophotoluminescence glass dosimeter (RPLGD) inserted in the position of an anthropomorphic Rando Phantom. Two Gy were prescribed and calculated with a tomotherapy planning machine for a 3-cm diameter spherical planning target volume (PTV) created in the lung area. Compatibility (measured dose/calculated dose and σ value=(D(meas)-D(calc))/D(prescribed)) × 100 (%)) was analyzed according to dosimeter location. RESULTS: Deviations between measured and calculated doses for the lung lesion were within 4% for planning target volume, indicating that adequate dose delivery to the PTV was achievable. On the other hand, we found dose deviations up to 15% for the lower prescribed dose range (64% or less) for the measured dose/calculated comparison and a 6% deviation according to the σ value in or near inhomogeneous tissue. CONCLUSION: Although the measured dose satisfied the clinical requirement in almost all areas including PTV, we should note that there may be discrepancies between expected calculated dose and irradiated dose in or near inhomogeneous area.