Fractionated stereotactic body radiation therapy for medically inoperable stage I lung cancer adjacent to central large bronchus.

PURPOSE

To assess the body-framed stereotactic body radiation therapy (SBRT) results and toxicity for medically inoperable stage I lung cancer adjacent to central large bronchus and then compare the results with those of SBRT in peripheral lung tumor in the aspects of survival and SBRT-related pulmonary toxicities.

MATERIALS

From June 1999 to May 2006, 32 patients diagnosed as stage I, T1N0 or T2N0, resectable NSCLC were treated with body-frame based fractionated SBRT. Thirty-one patients had several medical problems conflicting surgical procedure. Stereotactic body frame was used for improving setup accuracy. Doses of 10-20 Gy per fraction were delivered to the planning target volume (PTV) up to a total dose of 40-60 Gy with three to four fractions on consecutive days. Centrally located tumor was defined as the tumor within 2 cm apart from large bronchial tree, and was subdivided into bronchial (main/lobar bronchus) and peribronchial (segmental or distal).

RESULTS

Median follow-up was 26.5 months. The 6-month major response rate, including complete or partial response, was 53.1%. One patient showed progressive disease 1 month after SBRT. The 1- and 2-year actuarial local tumor control rates were both 85.3%. Overall survival was 70.9% at 1 year and 38.5% at 2 years, and survival was not correlated with SBRT dose. Of 9 patients with centrally located tumors, three (33%) experienced Grades 3-5 pulmonary toxicities. Eight patients showed partial or complete bronchial stricture and secondary loss of normal lung volume. Median time to bronchial stricture was 20.5 months. Overall survival did not differ by tumor location.

CONCLUSIONS

SBRT in this fractionation should not be given to central lung tumors because it can cause the late major airway toxicities in some patients. More protracted hypofractionated treatment regimen may be more safe than that used usually in SBRT for central lung tumors.