Stereotactic radiosurgery for treatment of spinal metastases recurring in close proximity to previously irradiated spinal cord.
OBJECTIVE
As the spinal cord tolerance often precludes reirradiation with conventional techniques, local recurrence within a previously irradiated field presents a treatment challenge.


METHODS
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 cm(3) (range, 0.2-128.6 cm(3)). 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 Gy(3) (range, 4.7-19.3 Gy(3)). 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 <15 Gy(10) were significant predictors of local failure on univariate and multivariate analyses. In patients with a retreatment interval of <12 months, 6/12 month local control rates were 88%/58%, with a SSED of >15 Gy(10), compared to 45%/0% with <15 Gy(10), respectively. One patient (2%) experienced Grade 4 neurotoxicity.


CONCLUSIONS
SRS is safe and effective in the treatment of spinal metastases recurring in previously irradiated fields. Tumor recurrence within 12 months may correlate with biologic aggressiveness and require higher SRS doses (SSED >15 Gy(10)). Further research is needed to define the partial volume retreatment tolerance of the spinal cord and the optimal target dose.
Department of Neurosurgery, Stanford University Medical Center, CA, USA.
Clara Y H
CY
Choi
John R
JR
Adler
Iris C
IC
Gibbs
Steven D
SD
Chang
Paul S
PS
Jackson
A Yuriko
AY
Minn
Robert E
RE
Lieberson
Scott G
SG
Soltys
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000601:surgery*; D011836:Radiation Tolerance; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D019233:Retreatment; D012189:Retrospective Studies; D013116:Spinal Cord / Q000528:radiation effects*; D013125:Spinal Neoplasms / Q000401:mortality / Q000473:pathology / Q000556:secondary / Q000601:surgery*; D015996:Survival Rate; D047368:Tumor Burden; D055815:Young Adult