Initial experience treating lung tumors with the cyberknife

Stereotactic body radiosurgery (SBRS) of lung tumors with the CyberKnife® (Accuray Incorporated, Sunnyvale, CA) achieves excellent rates of local disease control with limited toxicity to surrounding tissues. We retrospectively reviewed treatments and outcomes for 90 patients with 109 lung lesions treated at the CyberKnife Center of Miami between March 2004 and September 2006. This monotherapy review included 49 patients with 53 primary lung cancers, 27 patients with 42 pulmonary metastases, 6 patients with external beam failure and 8 patients treated by SBRS as a boost following or before conventionally fractionated radiotherapy (3DCRT or IMRT). In the primary tumor category, 43 patients remain alive. Thirty-two have been followed 1 to 25 months (median = 11.5 months). Fortynine percent (21/43) of them have had a complete radiographic response and have been followed for a median of 18.5 months. Another 8 have evidence of at least a partial radiographic response. There have been 5 failures (5/43) within the PTV, for a local recurrence rate of 11%. Of the total 109 treated lesions, 97/109 (89%) showed radiographic evidence of at least a partial response to treatment. Six of the failures were in lesions < 20 cc; 4 were in lesions 21-100 cc and 2 were in lesions > 100 cc. All of the patients tolerated SBRS well with fatigue as the main toxicity. Two patients required hospitalization for Grade III radiation pneumonitis. We conclude that the delivery of precisely targeted, high dose, hypofractionated irradiation to lung tumors with the CyberKnife is well tolerated and has outcomes that are comparable with published results for other methods of SBRS.