PURPOSE: We report our early success in the definitive treatment of small peripheral inoperable thoracic malignancies using the CyberKnife® frameless image-guided stereotactic radiosurgery system with the Synchrony™ motion tracking module.
METHODS: Inoperable patients with stage I non small cell lung cancer or single metastases to the lung (size < 4cm) received treatment with the CyberKnife stereotactic radiosurgery system utilizing the Synchrony™ motion tracking module. Multiple fiducials (3-5) were placed in close proximity to the tumors under CT-guidance. A treatment plan was created using a 5mm margin and an average of 167 beams ranging in diameter from 15-40 mm. Each patient received 45 - 60 Gy in three separate brief (< 2 hours) radiation treatments over a 3 to 11 day period (BED > 100 Gy in conventional fractionation). PET/CT imaging and pulmonary function testing were followed.
RESULTS: Between July 2004 and April 2006, 30 patients with 32 small (average size 2.0cm) peripheral lung tumors were treated. 63% were inoperable stage I lung cancer and 37% single metastases. 15% of patients were oxygen-dependent, 13% had previous conventional thoracic irradiation and 46% had prior lobar resection. CT-guided fiducial placement resulted in pneumothorax in 36% of patients (16% of all patients required chest tube insertion). CyberKnife treatment was short and well tolerated. Mild fatigue and transient soft tissue discomfort were the only acute side effects. Pneumonitis requiring steroid therapy was seen in six patients, two of which had extensive prior conventional thoracic radiation. At nine month follow-up there were four deaths, one secondary to metastatic progression and three to co-morbidities. All tumors responded to treatment. Interpretation of tumor response has been complicated by focal radiation fibrosis. Local progression was observed in one patient. There has been no evidence of regional lymph node recurrence.
CONCLUSION: CyberKnife® frameless image-guided fractionated high-dose stereotactic radiosurgery with the Synchrony™ motion tracking module is a promising, well-tolerated single modality treatment option for inoperable small peripheral lung tumors.
CLINICAL IMPLICATIONS: CyberKnife is a new treatment option for inoperable peripheral lung tumors.
DISCLOSURE: Brian Collins, Consultant fee, speaker bureau, advisory committee, etc. I have received honoraria from Accuray for lectures given in 2006.