Stereotactic body radiotherapy (SBRT) is widely used as a curative treatment option for
stage I non-small-cell lung cancer, but for patients with stage I small-cell lung cancer,
the role of stereotactic body radiotherapy is unclear. In this study, we retrospectively
analyzed the outcomes of a subset of patients with stage I small-cell lung cancer treated
with stereotactic body radiotherapy in the database of the Japanese Radiological
Society-Multi-Institutional stereotactic body radiotherapy Study Group. The 43 patients
treated with stereotactic body radiotherapy for stage I small-cell lung cancer between
2004 and 2012 at 11 Japanese institutions were studied: median age = 77 years; 32 (74%)
males and 11 females; and 80% were medically inoperable. The clinical stage was IA in 31
and IB in 12. In all patients, the lung tumors were pathologically proven as small-cell
lung cancer. A total dose of 48 to 60 Gy was administered in 4 to 8 fractions. The median
biologically effective dose (α/β = 10 Gy) was 105.6 Gy. Chemotherapy and prophylactic
cranial irradiation were administered in only 8 patients, respectively. The median
follow-up time was 23.2 months. The 2-year overall survival, progression-free survival,
and distant metastasis-free survival rates were 72.3%, 44.6%, and 47.2%, respectively. The
2-year local control was 80.2%. Regarding the patterns of failure, distant metastasis,
lymph node metastasis, and local recurrence were observed in 47%, 28%, and 16% of
patients, respectively. No ≥grade 3 stereotactic body radiotherapy-related toxicities were
observed. Although stereotactic body radiotherapy was thus revealed to be effective for
the local control of stage I small-cell lung cancer, the incidence of distant metastases
was high. Further investigations of larger cohorts are needed, including analyses of the
effects of combined chemotherapy.