To assess the impact of fractionation upon tumor control and toxicity in medically inoperable early stage lung cancer patients treated with stereotactic body radiotherapy.

We reviewed 94 consecutive stereotactic body radiotherapy treatments (86 patients) with medically inoperable stage I non-small cell lung cancer receiving either 50 Gy in five fractions (n = 56) or 60 Gy in three fractions (n = 38) from October 2003 to August 2007. Institutional practice was 10 Gy x 5 before March 1, 2006, when it changed to 20 Gy x 3 to conform to Radiation Therapy Oncology Group 0236 unless otherwise dictated clinically.

Median age was 73 years and median Karnofsky performance status 80. A total of 69 lesions were T1, 24 were T2 lung cancer. Median follow-up was 15.3 months. For the 50- and 60-Gy cohorts at 1 year, local control was 97.3% versus 100%, nodal failure 7.3% versus 3.4%, distant metastasis rate 21.8% versus 29.5%, and overall survival 83.1% versus 76.9% (p = 0.68, 0.54, 0.56, and 0.54, respectively). There was no difference in overall survival for patients with histologic (n = 61) compared with radiographic (n = 33) diagnosis. There was no impact of fractionation in the subset of T2 tumors. We observed two cases (2.2%) of clinical grade 2 pneumonitis. Mild late chest wall toxicity (grade 1 or 2) was seen in nine patients (10%) at a median of 8.4 months after treatment and was more common in the 60-Gy group (7 of 38 [18%] versus 2 of 56 [4%], p = 0.028).

Local control, overall survival, nodal failure, and distant failure were not affected by fractionation. Chest wall toxicity was more common with 60-Gy group.