Tolerance of the aorta using intraoperative iodine-125 interstitial brachytherapy in cancer of the lung

PURPOSE: A retrospective review to assess the efficacy and morbidity of surgical resection and I-125 interstitial lung brachytherapy placed in approximation to the aorta. METHODS AND MATERIALS: The records and postoperative films of 278 patients who had undergone intrathoracic I-125 brachytherapy at our institution were reviewed. All patients had undergone a gross total resection of a non-small-cell lung cancer using segmental resection, wedge resection, or sublobar resection. Frozen section margins of resection were required to be negative before the intra-operative delivery of the implant. Of those reviewed, 29 patients were implanted with I-125 impregnated Vicryl mesh that contacted greater than 50% with the aorta. Implants consisted of I-125 seeds sewn into a nomographically guided geometric array. Only implants where 50% or greater of the implant volume directly approximated the aorta were selected for inclusion into this study. The mean aortic volume receiving the entire prescribed dose was 17.2 cc (mean surface area = 34.4 cm(2)) and the mean prescribed dose was 114 Gy (range, 85-120) over the permanent life of the implant calculated by isodose curve distribution at a depth of 0.5 cm from the plane of the implant. Five patients have received postoperative mediastinal dose supplementation with external beam irradiation to further address occult mediastinal nodal disease not revealed during the intraoperative frozen section analysis. RESULTS: All patients tolerated the surgery and brachytherapy well with no perioperative mortality. With a median followup of 45.3 months (range, 1-117), 1 of the 29 patients suffered a fatal hemorrhage from suspected great vessel rupture. A review of this case demonstrated that the interstitial therapy had been supplemented with 4500 cGy of external irradiation, which overlapped a small portion of the implant volume overlying the aorta. No other patients suffered even minor events referable to the implant and have continued to do well without symptomatic evidence of chronic sequelae as of the publication of this article or the time of their death. Local control has been achieved in all patients still living and had been achieved in all patients who died from subsequent progression of metastatic disease or other cause. CONCLUSIONS: Interstitial I-125 intrathoracic brachytherapy is a safe and effective method when used with sublobar resection in high-risk stage I non-small-cell lung cancer patients and maybe used even in situations that require placement of the sources in close approximation to the aorta. The tolerance of the aorta seems to be greater than previously thought, and may well exceed 12,000 cGy over the permanent life of the interstitial implant. Interstitial I-125 brachytherapy can safely be used to deliver significant radiation dose indirect contact with the aorta but supplemental, overlapping external beam irradiation should be avoided. (C) 2008 American Brachytherapy Society. All rights reserved.