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Radiotherapy
treatment planning and long-term follow-up with [(11)C]methionine PET
in patients with low-grade astrocytoma
Nuutinen
J, Sonninen P, Lehikoinen P, Sutinen E, Valavaara R, Eronen E,
Norrgard S, Kulmala J, Teras M, Minn H
Department of Oncology and Radiotherapy, Turku University Central
Hospital, Turku, Finland.
Purpose. To evaluate the feasibility of
[(11)C]-methionine positron emission tomography (MET PET) in
radiotherapy (RT) treatment planning and long-term follow-up in
patients with low-grade glioma.
Patients. Thirteen patients with
low-grade astrocytoma and 1 with anaplastic astrocytoma underwent
sequential MET PET and magnetic resonance imaging (MRI) before and 3,
6, 12, and 21-39 months after RT, respectively.
Ten patients were
studied after initial debulking surgery or biopsy and 4 in the
recurrence phase.
Methods.
A total of 58 PET scans were performed.
After transmission scanning, a
median dose of 425 MBq of MET was injected intravenously and emission
data was acquired 20 min after injection for 20 min.
The uptake of MET
in tumor area was measured as standardized uptake value (SUV) and
tumor-to-contralateral brain SUV ratios were generated to assess
irradiation effects on tumor metabolism.
Functional imaging with PET
was compared with concurrent MRI in designing the RT planning volumes
and in assessment of response to RT during a median follow-up time of
33 months.
Results.
In 12 patients (86%), tumor area was clearly discernible in the
baseline PET study.
In the remaining 2 patients with a suspected
residual tumor in MRI, PET showed only a diffuse uptake of MET
interpreted as negative in the original tumor area.
In the dose
planning of RT, MET PET was helpful in outlining the gross tumor
volume in 3 of 11 cases (27%), whereas PET findings either coincided
with MRI (46%) or were less distinctive (27%) in other cases.
In
quantitative evaluation, patients with a low tumor SUV initially had
significantly better prognosis than those with a high SUV.
Tumor-to-contralateral brain uptake ratios of MET discriminated well
patients remaining clinically stable from those who have since
relapsed or died of disease.
Conclusion.
Quantitative MET PET has prognostic value at the time of initial
treatment planning of low-grade glioma.
Some patients may benefit of
RT volume definition with MET PET, which seems to disclose residual
tumor better than MRI in selected cases.
Stable or decreasing uptake
of MET in tumor area after RT during follow-up seems to be a favorable
sign.
PMID: 10924970 [PubMed - indexed for MEDLINE]
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