88: Innovative Radiation Techniques: Role of Brachytherapy and Intraoperative Radiotherapy in Treatment of Lung Cancer

Introduction

Brachytherapy, the use of radioactive isotopes placed directly on the desired target tissues during surgery or placed endoluminally, can be used for treatment of lung cancer. It offers several theoretic advantages when compared with traditional radiotherapy. Direct surgical placement of the radiation source allows for specific targeting and uniform delivery of the radiation minimizing the amount of normal lung in the radiation field. This potentially limits radiation side effects and ensures patient compliance which has been a major disadvantage of external beam radiation therapy.

Early Stage Lung Cancer

It has been established that lobectomy offers the best chance of cure for early-stage non–small-cell lung cancer. According to the Lung Cancer Study Group, sublobar or wedge resection is not as effective as lobectomy or pneumonectomy because it is associated with a high incidence of local recurrence.¹ However, a large resection requires the patient to have a reasonable residual forced expiratory volume in 1 second (FEV₁) of 0.8 to 1.2 L and a ventilation–perfusion scan corresponding to adequate breathing in other lung segments. Patients who have long histories of smoking commonly fail to have these advantageous characteristics. Techniques that combine sublobar resection with radiotherapy delivered intraoperatively or through the implantation of radioactive ¹²⁵I seeds at the lung resection margin have shown promising results (see section “planar seed experience”). This procedure has been reported to reduce local disease recurrence and improve palliation of symptoms. Additionally, it provides a treatment option for patients who are not physically capable of undergoing lobectomy or pneumonectomy or who are considered high-risk surgical candidates consequent to other comorbidities.

Varying systems for radiation delivery are presently used in clinical practice. Three techniques have been described for use following sublobar resection all of which are compatible with thoracoscopy.

Planar Seed Implant Technique

There are several reports of wedge resection procedures for stage I tumors that have been performed in conjunction with planar ¹²⁵I seed implants. This procedure has been reported to reduce local disease recurrence and improve local control.

After the wedge resection, the surgeon must measure the area at risk for length and width to determine the dimension of the implant. The implant is made of two components. The source material, called the Seed-in-Carrier, available through the Oncura Company (Plymouth Meeting, PA), consists of ¹²⁵I seeds that are embedded in strands of absorbable Vicryl suture. A second isotope recently became commercially available, using ¹³¹Cs, from Isoray Medical (Richland, WA). There are 10 seeds in each strand, and each seed and strand is spaced 1 cm apart center to center. The individual seed measures 0.7 × 4 mm in dimension. The source material is attached to an absorbable mesh material made of either Dacron or Vicryl that is custom trimmed to fit the area at risk. Before trimming, 1 cm is added to the overall ...