PURPOSE: To report clinical results from a prospective cohort of medically inoperable early stage lung cancer patients treated with stereotactic body radiotherapy (SBRT) employing intensity-modulated radiotherapy (IMRT) beams.
METHODS: Between 10/2003 and 3/2006, 43 lung tumor patients have been treated using SBRT. 28 had medically inoperable early stage lung cancer treated on a Novalis BrainLab unit with IMRT beams. After immobilization in a Novalis body cushion, compression by weighted abdominal belt was used to limit respiratory excursion. CT simulation images acquired at rest, at full inhalation, and at full exhalation were fused to generate an internal gross tumor volume (ITV) that reflected residual motion after external compression. Dose was prescribed using an IMRT approach to cover the planning target volume (PTV=ITV + 3-5 mm margin). SBRT was administered as 50 Gy in 5 sequential fractions of 10 Gy with 7 non-opposing, non-coplanar beams. IMRT calculations included heterogeneity corrections. Follow-up was at 6 weeks and then every three months.
RESULTS: For 28 patients, mean age was 65 years (range 54-87). There were 16 males (57%). Mean follow-up was 9 months (range 1.5-24). Tissue diagnosis was contraindicated in 8 (29%); PET was absent in 2 (7%). Lesions were: 18 T1 (64%); 7 T2 (25%); 3 scar recurrence (11%). All SBRT was completed without interruptions. There was no acute esophagitis; 1 of 38 (2.6%) had acute grade 2 pneumonitis. To date there are no delayed lung toxicities≥grade 2.There were 10/38 (26%) complete responses, 26/38 (69%) partial responses, 2/38 stable disease (5%). Local control and overall survival at 1 year are 96.4% and 93%, respectively; two patients failed regionally (7%) and 4 (14%) distantly.
CONCLUSION: Mindful of the limited follow-up, IMRT-based delivery of SBRT demonstrates a high response rate and excellent local control. There are minimal acute treatment-related toxicities and no treatment related deaths.
CLINICAL IMPLICATIONS: IMRT-based SBRT is feasible and effective for a challenging medical population.
DISCLOSURE: Gregory Videtic, None.