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

Abstract 

Purpose

A retrospective review to assess the efficacy and morbidity of surgical resection and ¹²⁵I interstitial lung brachytherapy placed in approximation to the aorta.

Methods and materials

The records and postoperative films of 278 patients who had undergone intrathoracic ¹²⁵I 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 intraoperative delivery of the implant. Of those reviewed, 29 patients were implanted with ¹²⁵I impregnated Vicryl mesh that contacted greater than 50% with the aorta. Implants consisted of ¹²⁵I 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 17.2cc (mean surface area=34.4cm²) and the mean prescribed dose was 114Gy (range, 85–120) over the permanent life of the implant calculated by isodose curve distribution at a depth of 0.5cm 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 4500cGy 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 ¹²⁵I 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 may be 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 12,000cGy over the permanent life of the interstitial implant. Interstitial ¹²⁵I brachytherapy can safely be used to deliver significant radiation dose in direct contact with the aorta but supplemental, overlapping external beam irradiation should be avoided.

Keywords: Aortic tolerance, Sublobar resection, Lung cancer, Brachytherapy, Vascular radiation tolerance