Correlation of local failure with measures of dose insufficiency in the high-dose single-fraction treatment of bony metastases.
OBJECTIVE
In the setting of high-dose single-fraction image-guided radiotherapy of spine metastases, the delivered dose is hypothesized to be a significant factor in local control. We investigated the dependence of local control on measures of dose insufficiency.


METHODS
The minimum doses received by the hottest 100%, 98%, and 95% (D(min), D(98), and D(95)) of the gross target volume (GTV) were computed for 91 consecutively treated lesions observed in 79 patients. Prescribed doses of 18-24 Gy were delivered in a single fraction. The spinal cord and cauda equina were constrained to a maximum dose of 12-14 Gy and 16 Gy, respectively. A rank-sum test was used to assess the differences between radiographic local failure and local control.


RESULTS
With a median follow-up of 18 months, seven local failures have occurred. The distributions of GTV D(min), D(98), and D(95) for treatments resulting in local failure were found to be statistically different from the corresponding distributions of the patient group as a whole. Taking no account of histology, p values calculated for D(min), D(98), and D(95) were 0.004, 0.012, and 0.031, respectively. No correlations between local failure and target volume or between local failure and anatomic location were found.


CONCLUSIONS
The results indicate that D(min), D(98), and D(95) may be important risk factors for local failure. No local failures in any histology were observed when D(min) was >15 Gy, suggesting that this metric may be an important predictor of local control.
Lovelock
D Michael
DM
Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA. lovelocm@mskcc.org
Zhang
Zhigang
Z
Jackson
Andrew
A
Keam
Jennifer
J
Bekelman
Justin
J
Bilsky
Mark
M
Lis
Eric
E
Yamada
Yoshiya
Y
D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy* / Q000556:secondary; D018450:Disease Progression; D006801:Humans; D010384:Pelvic Bones / Q000000981:diagnostic imaging; D019736:Prostheses and Implants; D011859:Radiography; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy* / Q000556:secondary; D017211:Treatment Failure; D047368:Tumor Burden