Abstract
Objective
To determine whether biological effective dose (BED) was predictive of obliteration
after stereotactic radiosurgery (SRS) for cerebral arteriovenous malformations (AVMs).
Patients and Methods
We studied patients undergoing single-session AVM SRS between January 1, 1990, and
December 31, 2014, with at least 2 years of imaging follow-up. Excluded were patients
with syndromic AVM, previous SRS or embolization, and patients treated with volume-staged
SRS. Biological effective dose was calculated using a mono-exponential model described
by Jones and Hopewell. The primary outcome was likelihood of total obliteration defined
by digital subtraction angiography or magnetic resonance imaging (MRI). Variables
were analyzed as continuous and dichotomous variables based on the maximum value of
(sensitivity–[1–specificity]).
Results
This study included 352 patients (360 AVM, median follow-up, 5.9 years). The median
margin dose prescribed was 18.75 Gy (interquartile range [IQR]: 18 to 20 Gy). Two
hundred fifty-nine patients (71.9%) had obliteration shown by angiography (n=176)
or MRI (n=83) at a median of 36 months after SRS (IQR: 26 to 44 months). Higher BED
was associated with increased likelihood of obliteration in univariate Cox regression
analyses, when treated as either a dichotomous (≥133 Gy; hazard ratio [HR],1.52; 95%
confidence interval [CI], 1.19 to 1.95; P<.001) or continuous variable (HR, 1.00, 95% CI, 1.0002 to 1.005; P=.04). In multivariable analyses including dichotomized BED and location, BED remained
associated with obliteration (P=.001).
Conclusion
Biological effective dose ≥133 Gy was predictive of AVM obliteration after single-session
SRS within the prescribed margin dose range 15 to 25 Gy. Further study is warranted
to determine whether BED optimization should be considered as well as treatment dose
for AVM SRS planning.
Abbreviations and Acronyms:
AVM (arteriovenous malformation), BED (biological effective dose), CI (confidence interval), IQR (interquartile range), PIV (prescription isodose volume), RR (relative risk), TDR (treatment dose rate)To read this article in full you will need to make a payment
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Article info
Footnotes
Potential Competing Interests: Dr Brown reports personal fees from UpToDate (contributor), outside the scope of this work. Dr Foote reports grants from Hitachi, LTD, and financial support from Elsevier (textbook editor), UpToDate, (contributor), the American Board of Radiology (member with reimbursement for travel), NCCN (member with reimbursement for travel), Alliance for Proton Therapy Access (advisory board member), and the Cancer Terminator Foundation (member, scientific advisory board). Dr Foote has a patent with royalties paid to Bionix. All contributions to Dr Foote are outside the context of this work. All other authors report no competing interests.
Data Previously Presented: Preliminary data for this study were presented as a mini-podium presentation at the 2019 Congress of Neurological Surgeons meeting in San Francisco, California, October 19 to 23. This study has not been otherwise presented or published elsewhere.
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- Stereotactic Radiosurgery: From a Prescribed Physical Radiation Dose Toward Biologically Effective DoseMayo Clinic ProceedingsVol. 96Issue 5
- PreviewRadiosurgery or stereotactic radiosurgery was invented by Swedish neurosurgeon Lars Leksell in 1951. Leksell defined radiosurgery as “delivery of a single, high dose of irradiation to a small and critically located intracranial volume through the intact skull.” His initial efforts were focused on developing a noninvasive method to create lesions within the brain, using radiation rather than a conventional blade. In 1968, the first Gamma Knife (GK) unit (Elekta AB) appeared in Stockholm, using multiple cobalt 60 sources of radiation (currently 192 sources).
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