title: Long-term outcomes of stereotactic body radiation therapy (SBRT) with fiducial tracking for inoperable stage I non-small cell lung cancer (NSCLC).
abstract: BACKGROUND
  Stereotactic body radiation therapy (SBRT) for stage I non-small cell lung cancer (NSCLC) is considered standard of care in the medically inoperable patient population. Multiple methods of SBRT delivery exist including fiducial-based tumor tracking, which allows for smaller treatment margins and avoidance of patient immobilization devices. We explore the long-term clinical outcomes of this novel fiducial-based SBRT method.
  
  
  METHODS
  In this single institutional retrospective review, we detail the outcomes of medically inoperable pathologically confirmed stage I NSCLC. Patients were treated with the Cyberknife SBRT system using a planning target volume (PTV) defined as a 5-mm expansion from gross tumor volume (GTV) without creation of an internal target volume (ITV). Dose was delivered in three or five equal fractions of 10 to 20 Gy. Pretreatment and posttreatment pulmonary function test (PFT) changes and evidence of late radiological rib fractures were analyzed for the majority of patients. Actuarial local control, locoregional control, distant control, and overall survival were calculated using the Kaplan-Meier method.
  
  
  RESULTS
  Sixty-one patients with a median age of 75 years were available for analysis. The majority (80 %) of patients were deemed to be medically inoperable due to underlying pulmonary dysfunction. Eleven patients (18 %) developed symptomatic pneumothoraces secondary to fiducial placement under CT guidance, which precipitously dropped to 0 % following transition to bronchoscopic fiducial placement. The 2-year rib fracture risk was 21.4 % with a median time to rib fracture of 2.9 years. PFTs averaged over all patients and parameters demonstrated small absolute declines, 5.7 % averaged PFT decline, at approximately 1 year of follow-up, but only the diffusing capacity of lung for carbon monoxide (DLCO) demonstrated a statistically significant decline (10.29 vs. 9.01 mL/min/mmHg,p= 0.01). Five-year local control, locoregional control, and overall survival were 87.6, 71.8, and 39.3 %, respectively.
  
  
  CONCLUSIONS
  Despite reduced treatment margins and lack of patient immobilization, SBRT with fiducial-based tumor tracking achieves clinically comparable long-term outcomes to other linac-based SBRT approaches.
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital, Lower Level Bles, 3800 Reservoir Road, N.W, Washington, DC 20007 USA.
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Lischalk
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital, Lower Level Bles, 3800 Reservoir Road, N.W, Washington, DC 20007 USA.
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Woo
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital, Lower Level Bles, 3800 Reservoir Road, N.W, Washington, DC 20007 USA.
authors.forename: Shaan
authors.initials: S
authors.lastname: Kataria
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital, Lower Level Bles, 3800 Reservoir Road, N.W, Washington, DC 20007 USA.
authors.forename: Nima
authors.initials: N
authors.lastname: Aghdam
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital, Lower Level Bles, 3800 Reservoir Road, N.W, Washington, DC 20007 USA.
authors.forename: Ima
authors.initials: I
authors.lastname: Paydar
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital, Lower Level Bles, 3800 Reservoir Road, N.W, Washington, DC 20007 USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Repka
authors.affiliation: Division of Pulmonary, Critical Care, and Sleep Medicine, Georgetown University Hospital, Pasquerilla Healthcare Center, 5th floor, 3800 Reservoir Road, N.W., Washington, DC 20007 USA.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Anderson
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital, Lower Level Bles, 3800 Reservoir Road, N.W, Washington, DC 20007 USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Collins
keywords: Fiducial markers; Lung neoplasms; Non-small cell lung cancer; Pulmonary function test; Stereotactic body radiation therapy