Impact of dose on local failure rates after image-guided reirradiation of recurrent paraspinal metastases.
OBJECTIVE
To examine the impact of dose on local failure (LF) rates in the re-treatment of recurrent paraspinal metastases with image-guided intensity-modulated radiotherapy (IG-IMRT).


METHODS
The records of patients with in-field recurrence after previous spine radiation (median dose, 30 Gy) who received salvage IG-IMRT with either five 4-Gy (20-Gy group, n = 42) or five 6-Gy (30-Gy group, n = 55) daily fractions between January 2003 and August 2008 were reviewed. Institutional practice was 20 Gy before April 2006, when it changed to 30 Gy. A total of 47 cases (48%) were treated adjuvantly, after surgery to decompress epidural disease. LF after IG-IMRT was defined radiographically.


RESULTS
The median follow-up was 12.1 months (range, 0.2-63.6 months). The 1-year cumulative incidences of LF after 20 Gy and 30 Gy IG-IMRT were 45% and 26%, respectively (p = 0.04). Of all treatment characteristics examined (20-Gy vs. 30-Gy dose group, dose to 95% of the planned and gross target volume, tumor size, histology, receipt of surgery, and interval between first and second radiation), only dose group had a significant impact on actuarial LF incidence (p = 0.04; unadjusted HR, 0.51; 95% CI, 0.27-0.96). There was no incidence of myelopathy.


CONCLUSIONS
A significant decrease in LF after IG-IMRT with five 6-Gy fractions compared with five 4-Gy fractions was observed without increased risk of myelopathy. Until prospective data comparing stereotactic hypofractionated and single-fraction regimens become available, when reirradiating recurrent paraspinal metastases with IG-IMRT, administration of five 6-Gy daily fractions is reasonable.
Damast
Shari
S
Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA. damasts@mskcc.org
Wright
Jean
J
Bilsky
Mark
M
Hsu
Meier
M
Zhang
Zhigang
Z
Lovelock
Michael
M
Cox
Brett
B
Zatcky
Joan
J
Yamada
Yoshiya
Y
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019299:Decompression, Surgical; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000379:methods; D019233:Retreatment / Q000379:methods; D013125:Spinal Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary* / Q000601:surgery; D017211:Treatment Failure; D047368:Tumor Burden; D055815:Young Adult