Single fraction stereotactic radiosurgery (SFSR) for lung tumors - A phase I dose escalation trial

Abstract

7231 Background: Although stereotactic radiosurgery is well established for the treatment of intracranial neoplasms, its use for lung tumors is novel. We report preliminary results of SFSR in patients with inoperable lung tumors in a phase I study. Methods: Eligible patients included those with inoperable early stage (T1–2N0) non-small cell lung cancers (NSCLC) or solitary lung metastases. Treatments were delivered via a linear accelerator mounted on a computer-control robotic arm (Cyberknife, Accuray, CA). Before treatment, all patients underwent CT-guided metallic fiducial placement in the tumor for image guided targeting, which when combined with breath-holding ensures accurate tumor targeting. All radiation treatments were delivered in a single fraction. 9 to 10 patients were treated per dose cohort starting at 15 Gy/fraction followed by dose escalation of 5–10 Gy/fraction. A minimal 3 month period is required between each dose level for monitoring toxicity. Results: Nineteen patients (11 NSCLC and 8 metastatic tumors) were enrolled to date. The median age was 74 (range: 22–83). Tumor size ranged from 1.5 to 5 cm in maximal dimension. Nine patients received 15 Gy and 10 received 25 Gy. There were 2 complications related to fiducial placement - 1 pneumothorax requiring chest tube insertion and 1 emphysema exacerbation. One patient with prior thoracic irradiation for a separate esophageal cancer developed grade 3 radiation pneumonitis at 3 months post treatment. She subsequently died at 6 months post treatment with an enlarging pleural effusion in the face of both radiation-pneumonitis and tumor progression. For the remaining patients, there was no obvious clinical decline in pulmonary function. 17 patients were evaluable for radiographic response, which was scored as stable in 1, minor in 6, partial in 6 and complete in 4. 3 complete responders received 25 Gy. At a median follow up of 8 months (range 1–32), 4 have relapsed locally, all in the 15 Gy dose group. Conclusions: SFSR is feasible and well tolerated for the treatment of selected lung tumors. Additional dose escalation is underway to determine the optimal radiation dose and overall treatment efficacy. No significant financial relationships to disclose.