Magnetic Resonance Imaging MRI T1 and T2 Volumetric Changes and Their Implications After Hypofractio

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Magnetic Resonance Imaging (MRI) T1 and T2
Volumetric Changes and Their Implications After
Hypofractionated Stereotactic Radiosurgery (SRS)
in Patients with Recurrent Malignant
Gliomas Amanda L. Schwer1, Brian D. Kavanagh1,
Robert McCammon1, Laurie E. Gaspar1, Jody
Tanabe2, Betty K. Demasters3, Kelly Stuhr1,
Changhu Chen1, MD. Departments of 1Radiation
Oncology, 2Radiology, and 3Pathology, University
of Colorado Health Sciences Center
Purpose/Objective To evaluate brain MRI T1 and
T2 volumetric changes after hypofractionated
stereotactic radiosurgery (SRS) and gefitinib.
-A 3rd patient who experienced an asymptomatic
increase in T1C after SRS was followed. After a
peak increase at 9 mo., the T1C has now declined
to 50 of the max. at 15 mo. (Figure 2).
-Median percentage increase in T2 volume likewise
trended upwards after SRS, from 14.8 at 1 month
up to 122.2 at 6 months. -Two pts who
experienced increases in their T1C volume
post-SRS underwent re-resection with both
specimens revealing only extensive radiation
necrosis (Figure 1).
-For the entire group, a greater increase in the
post-SRS T1C volume was associated with more
favorable prognosis survival of patients who
experienced a gt 150 increase in their T1C 5
months post-SRS was significantly greater than
those who did not (25.3 vs. 5.35 months, p
.008). (Figure 3).
Materials/Methods Patients with recurrent
high-grade gliomas were treated on a phase I SRS
dose escalation study. SRS consisted of 3
fractions delivered over 3 consecutive days. The
dose was escalated safely from 18 to 36Gy. The
target volume was the T1 contrast-enhancing (T1C)
lesion2 mm. Gefitinib was given at a dose of
250mg daily for gt 1 year. Brain MRIs were
performed routinely and all images were uploaded
into the BrainSCANTM SRS planning system. T1C
and T2 abnormalities were outlined on each MRI
slice and volumes were calculated.
Figure 1 T1 and T2 MRI images from one treated
patient (at pre-treatment, 1, 3, 5, 6, 9, and 12
mo. Patient underwent resection between the 5
and 6 month scans
Figure 3 Survival outcomes based on T1C
percentage changes.
Conclusions Most patients treated on this study
of SRS and gefitinib experienced a notable
increase in T1C and T2 volumes on MRI after
treatment. Interestingly, those patients with the
most dramatic early increase in MRI enhancement
ultimately had superior overall survival,
suggesting that the increased enhancement signals
a favorable reaction to treatment. We suggest
conservative management for patients exhibiting
early post-SRS MRI changes in view of the
observation that a transient exaggerated post-SRS
inflammatory/necrotic reaction may occur.
Figure 2 T1C MRI images (pre-txt and 3, 6, 12,
15 18mo. post-txt) from a patient whose volume
increases after SRS (30 Gy in 3fx) were observed
without intervention. The PTV is outlined
(purple), as are selected isodose lines 30Gy
(red), 20Gy (green) and 10Gy (blue). The middle
column represents isocenter slice, with the left
column one slice above and the right column one
slice below. Follow-up MRIs have been fused with
the initial pre-SRS scan to allow comparison of
changes in tissue in the same location. Note
that the enhancement increases initially,
stabilizes during gefitinib administration, and
then decreases after discontinuation of gefitinib
(15 and 18 mo. scans).
Results -87 MRI studies from 15 patients -Median
pre-treatment T1C vol. 40.9cc -Median
pre-treatment T2 vol. 184.1cc -Median post-SRS
percentage increases in T1C volume at 1, 2, 3, 4,
5, and 6 months were 8.9, 6.9, 57.3, 65.8, 92.8
and 152.2, respectively.