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A phase II trial of accelerated
radiotherapy using weekly stereotactic conformal boosts for
supratentorial glioblastoma multiforme. RTOG-0023
R. Cardinale, M.
Won, A. Choucair, M. Gillin, A.
Chakravarti, C. Schultz, L. Souhami, A.
Chen, H. Pham and M. Mehta
Medcl Coll of Virginia, Richmond,
VA; RTOG Headquarters, Philadelphia, PA; Univ of Wisconsin, Madison,
WI; M.D. Anderson Cancer Ctr, Houston, TX; MA Gen Hosp, Boston, MA;
Medcl Coll of Wisconsin, Milwaukee, WI; McGill Univ, Montreal, PQ,
Canada; U. of CA, Davis, CA; Virginia Mason Medcl Ctr, Seattle, WA
Background. Malignant
gliomas undergo molecular changes during radiation therapy
(RT) that lead to accelerated proliferation.
This phase II trial was performed to assess the feasibility,
toxicity, and efficacy of dose-intense RT employing weekly
fractionated stereotactic radiotherapy (FSRT) boosts for
patients with glioblastoma multiforme (GBM).
Methods. Patients with
histologically confirmed GBM with postoperative enhancing
tumor plus tumor cavity diameter ≤ 60 mm were
enrolled.
50 Gy of standard RT was given in daily 2 Gy
fractions.
In addition, patients received four FSRT treatments, once
weekly, during weeks 3–6 in lieu of standard RT to the
postoperative tumor bed plus enhancing tumor plus 5 mm (PTV).
FSRT dosing of either 7 Gy (PTV ≤ 40 mm) or 5 Gy (PTV > 40
mm) per fraction was given for a cumulative dose of 70 or
78 Gy in 29 (25 standard RT + 4 FSRT) treatments over 6
weeks.
A relocatable frame and shaped conformal fields were used
for FSRT.
Following the RT course, BCNU at 80 mg/m2 was
given for 3 days, q 8 weeks, for 6 cycles.
The sample size was calculated to compare survival with
RTOG-RPA class using one-sided p-values and calculated hazard
ratios.
Results. 76 patients were
analyzed.
Significant RT toxicity included: one grade 4 acute
(lethargy) and one grade 3 late (necrosis).
The median survival time (MST) was 12.5 months.
No survival difference is seen compared to the RTOG historical database.
Matched pair cox regression also showed no significant survival
difference.
For RPA class IV patients (50% of total) the MST was 14.7
mos. compared to 11.3 mos. for historic controls (p=0.15).
Patients with gross total resection (41%) had a MST of 16.1
mos. vs. 12.0 mos. for historic controls (p=0.19).
RT quality control was favorable with 90% compliance.
Conclusion. This
initial RTOG trial employing FSRT was feasible and well tolerated.
There appears to be no significant survival benefit for GBM
patients using this dose-intense, accelerated RT regimen although
RPA class IV and gross total resection patients trended toward
improved outcome.
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