Predictors of local control after single-dose stereotactic image-guided intensity-modulated radiotherapy for extracranial metastases.
OBJECTIVE
To report tumor local control after treatment with single-dose image-guided intensity-modulated radiotherapy (SD-IGRT) to extracranial metastatic sites.


METHODS
A total of 126 metastases in 103 patients were treated with SD-IGRT to prescription doses of 18-24 Gy (median, 24 Gy) between 2004 and 2007.


RESULTS
The overall actuarial local relapse-free survival (LRFS) rate was 64% at a median follow-up of 18 months (range, 2-45 months). The median time to failure was 9.6 months (range, 1-23 months). On univariate analysis, LRFS was significantly correlated with prescription dose (p = 0.029). Stratification by dose into high (23 to 24 Gy), intermediate (21 to 22 Gy), and low (18 to 20 Gy) dose levels revealed highly significant differences in LRFS between high (82%) and low doses (25%) (p < 0.0001). Overall, histology had no significant effect on LRFS (p = 0.16). Renal cell histology displayed a profound dose-response effect, with 80% LRFS at the high dose level (23 to 24 Gy) vs. 37% with low doses (≤22 Gy) (p = 0.04). However, for patients who received the high dose level, histology was not a statistically significant predictor of LRFS (p = 0.90). Target organ (bone vs. lymph node vs. soft tissues) (p = 0.5) and planning target volume size (p = 0.55) were not found to be associated with long-term LRFS probability. Multivariate Cox regression analysis confirmed prescription dose to be a significant predictor of LRFS (p = 0.003).


CONCLUSIONS
High-dose SD-IGRT is a noninvasive procedure resulting in high probability of local tumor control. Single-dose IGRT may be effectively used to locally control metastatic deposits regardless of histology and target organ, provided sufficiently high doses (> 22 Gy) of radiation are delivered.
Greco
Carlo
C
Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
Zelefsky
Michael J
MJ
Lovelock
Michael
M
Fuks
Zvi
Z
Hunt
Margie
M
Rosenzweig
Kenneth
K
Zatcky
Joan
J
Kim
Balem
B
Yamada
Yoshiya
Y
D000310:Adrenal Gland Neoplasms / Q000532:radiotherapy / Q000556:secondary; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001859:Bone Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D015179:Colorectal Neoplasms / Q000473:pathology; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology; D008113:Liver Neoplasms / Q000532:radiotherapy / Q000556:secondary; D008175:Lung Neoplasms / Q000532:radiotherapy / Q000556:secondary; D008207:Lymphatic Metastasis / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D011471:Prostatic Neoplasms / Q000473:pathology; D011832:Radiation Injuries / Q000473:pathology; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012074:Remission Induction; D012983:Soft Tissue Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D047368:Tumor Burden