Stereotactic Radiosurgery for Treatment of Spinal Metastases Recurring in Close Proximity to Previously Irradiated Spinal Cord

Purpose As the spinal cord tolerance often precludes reirradiation with conventional techniques, local recurrence within a previously irradiated field presents a treatment challenge. Methods and Materials We retrospectively reviewed 51 lesions in 42 patients treated from 2002 to 2008 whose spinal metastases recurred in a previous radiation field (median previous spinal cord dose of 40 Gy) and were subsequently treated with stereotactic radiosurgery (SRS). Results SRS was delivered to a median marginal dose of 20 Gy (range, 10–30 Gy) in 1–5 fractions (median, 2), targeting a median tumor volume of 10.3 cm3 (range, 0.2–128.6 cm3 ). Converting the SRS regimens with the linear quadratic model (α/β = 3), the median spinal cord maximum single-session equivalent dose (SSED) was 12.1 Gy3 (range, 4.7–19.3 Gy3 ). With a median follow-up of 7 months (range, 2–47 months), the Kaplan-Meier local control and overall survival rates at 6/12 months were 87%/73% and 81%/68%, respectively. A time to retreatment of ≤12 months and the combination of time to retreatment of ≤12 months with an SSED of